Published by MALAYSIAN PALM OIL COUNCIL2nd Floor,Wisma Sawit Lot 6, SS6, Jalan Perbandaran,47301 Kelana Jaya, Selangor, Malaysia.

Copyright © 2010 Kurt G. Berger

All rights reserved. No part of this book may be reproduced in any form or by any meanswithout prior permission from the Publisher.

National Library of Malaysia Cataloguing-In-Publication Data

Berger, Kurt G.Quality and functions of palm oil in food applications: a layman's guide/ Kurt G. Berger ISBN 978-983-9191-09-7I. Palm oil -- Quality. 2. Palm oil--By product. 3. Palm Products--Malaysia I.Title633.85109595

FOREWORD

While working at the Palm Oil

Research Institute of Malaysia (now the

Malaysian Palm Oil Board) in the 1980s

I received a phone call from a social

acquaintance involved in the palm oil

trade, asking "I say old chap, what's a

fatty acid then?" It was not difficult to

help him.

Reflecting on the question later it

occurred to me that many of the peo-

ple involved in palm oil, from growing through to end use, would surely find it interesting

and of benefit to know something of the basic technology.

That thought led to a series of articles in the Global Oils & Fats Business Magazine

(GOFB). There were two main objectives.The first was to describe the parameters used

to judge the quality of the product and the measures needed to ensure its good arrival

at the user, and the second was to provide information on how it is used in food pro-

duction around the world and, with it, to give some insight into the fascinating scientif-

ic aspects of food.

My own involvement in palm oil dates back to my time in the London research laborato-

ries of a large food manufacturer. In 1953 the British food industry was finally liberated from

the shackles of the wartime Food Ministry control, and we started to experiment with

palm oil, which was a new ingredient to us.We found that it was functional and economic

in a number of our products.

This work led 20 years later to an invitation to talk about our experience at a two-day con-

ference in London dealing with palm oil from the planting to the eating. One of the other

speakers was Tan Sri Borg Bek-Nielsen. When we met again in 1976 he remembered my

presentation and said: "We are thinking of starting a Research Institute for palm oil and you

must come and help us when we are ready."

Two years later a formal invitation came, which I was able to accept. There followed an

exciting and busy eight years in Malaysia. First we needed to draft a research programme

and agree it with the technical committee of the industry; next, to establish temporary lab-

oratories, for which we found two shophouses in the suburbs of Kuala Lumpur; and then

came the planning of permanent buildings and selection of a site for the Institute.

Chemical research started in 1979 and within two years yielded results that were suitable

for presenting at an international palm oil conference organised by the Incorporated

Society of Planters.

Staff for the Technical Advisory Service were recruited in 1980 and soon started to inves-

tigate the potential uses of palm oil around the world, feeding back to the Food Technology

Unit any problems that needed practical investigation. It was important to publicise useful

results at international conferences and to take part in government-led trade missions.

Not surprisingly perhaps, we found people who were suspicious of an ingredient unknown

to them after using only their traditional ingredients for many years.At that time, only west-

ern Europe was knowledgeable about palm oil.To develop some confidence in the prod-

uct, a Familiarisation Programme was instituted; key people in government offices and

industry in developing countries were invited at the Institute's expense to visit Malaysia for

two weeks.They were shown the plantations, the refineries and the work of the research

institute and given opportunities to talk to all those concerned.

This programme continues today, and there is no doubt that the friendly contacts made

have oiled the wheels of commerce. It proved particularly useful in a number of countries

where purchasing decisions were made in government offices with little technical know-

how.

It is similarly urgent today to inform present and potential importers of palm oil's versatil-

ity in application in their accustomed food products.This book is based on the GOFB series

of articles, edited and brought up to date.

Kurt Berger

Food Technology Consultant, UK

CHAPTER 1Basic chemistry of fats

CHAPTER 2Tests of quality

CHAPTER 3Quality during transport

CHAPTER 4Bakery products

CHAPTER 5Aerated dairy products

CHAPTER 6Butter alternatives

CHAPTER 7The lauric oils

CHAPTER 8Confectionery fats

CHAPTER 9Frying oils

CHAPTER 10Low trans fats formulae

CHAPTER 11Palm-based oleochemicals

CHAPTER 12Oils and fats properties

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CHAPTER 1: BASIC CHEMISTRY OF FATS

Technical aspects of oils and fats are of importance to those in the business.This chapter

examines the chemical composition of oils and fats.

Nine propositions cover the basic chemical information required to understand the main

technical terms used in the oils and fats industry (see Box).

8

PHYSICAL PROPERTIES

What makes fats solid and oils liquid? More details about fatty acids are useful in answer-

ing this. At first sight, one would think that a double bond would be stronger than a single

one in linking the Carbon chain. However, the two bonds involved are bent out of their nat-

ural position and therefore are under strain. So, a double bond is actually weaker.

9

So triglycerides containing only or mainly straight saturated acids align easily together to form

crystals. Such triglycerides are solid at room temperature.The kink in the unsaturated acids

makes it more difficult for their triglycerides to align and form crystals, so they stay liquid.

Most of the major vegetable oils contain mainly unsaturated fatty acids and are liquid at

room temperature.These consist of soybean, rapeseed, sunflower, cottonseed, groundnut,

olive and maize oils.

The most important exception is palm oil.With 50% unsaturated and 50% saturated acids, it

has a solid consistency at room temperature and is therefore unusual among vegetable oils.

Coconut and palm kernel oils are also solid due to their unusual content of short and medi-

um chain saturated acids. They have special applications in food and in the oleochemical

industry. In terms of world supply, they are available in relatively small amounts.

FOOD USES

Many of the food uses of oils and fats depend on the consistency or body. A simple exam-

ple - you can't pour margarine or butter on salad, and you can't spread olive oil on bread.

A solid character to a varying degree is necessary in fats for margarine, for bakery prod-

ucts, for ice cream. Historically, this solid character was provided by animal fats, but these

are little used in margarine and bakery fats nowadays.

The liquid oils can be modified to have a solid consistency by hydrogenation. Hydrogen is

added to some of the unsaturated component fatty acids, so increasing the average satu-

ration of the oil. The process takes place at around 100°C when the oil is mixed with

hydrogen gas in the presence of a catalyst. This sounds very simple but at the molecular

level there is a complication.

During hydrogenation the unsaturated acid has to go through an intermediate stage. At

this point the kink at the double bond is ironed out, the chain becomes straight but the

double bond is still there. It is now a 'trans' unsaturated fatty acid (trans fat). Partly-hydro-

genated oils always contain a mixture of saturated acids, unchanged unsaturated acids and

trans fats.

Trans fats are now known to be nutritionally undesirable, since research has shown that

they raise the level in the blood of undesirable 'LDL cholesterol' which is involved in the

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process of clogging up the arteries. At the same time they also decrease the blood level of

the desirable 'HDL cholesterol' which removes excess cholesterol from the blood stream.

This doubly adverse result is now universally recognised and has led national and interna-

tional expert bodies to advise minimising trans fats in foods.

Some countries have labelling laws to declare the trans fats content in food products.

Denmark has imposed a legal limit on the amount. Consumer awareness of nutritional

issues is high everywhere and food industry management is therefore strongly motivated

to remove trans fats from products. In the UK a large supermarket is stating that most of

its products are now free of trans fats, and the rest are following.

Two approaches are used to make consistent fats without trans fats:

1. If you completely hydrogenate liquid oil, so that all double bonds are saturated, clearly

you no longer have any trans fats. However, such a fat is as hard as bricks and, on its own,

of no use in food.

Another simple chemical process, 'interesterification' comes into play.The fully saturated

fat is melted and mixed with liquid oil.A catalyst is added, which induces all the fatty acids

to disconnect from their glycerol and re-attach to some other available glycerol in a ran-

dom manner. If you get the right proportions of the ingredients, you finish with a fat of

just the desired consistency.

2. The second approach uses palm oil or its higher melting fraction, palm stearin, either in

a mixture with other oils, or by using the interesterification procedure on a mixture

designed to get the characteristics needed.

The choice between the two approaches will depend on circumstances; for example, the

availability of locally produced oils may point to the first method. In many situations the

palm oil method is the more economic, as in the USA.

The steady increase in recent USA imports (Figure 1) shows that some manufacturers

have been taking advantage of the 'solid fat' properties of palm oil and palm stearin

since 2000. This trend can confidently be predicted to continue. Some commercial

firms in the USA already offer palm-based products for formulations that are free of

trans fats.

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Interchangeable use

A degree of interchangeability of oils is welcomed by the food industry as it gives the buyer

a choice of the cheaper supply. But just how interchangeable are vegetable oils? This answer

very much depends on the intended use.

For example, when selecting the solid component for a margarine formula, it was possible

to choose between partly hydrogenated soybean, rapeseed or other liquid oil and palm oil.

Today this option is much less available due to marketing considerations; palm oil is there-

fore a unique ingredient for this purpose.

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For use as a salad oil it is desirable that the oil should remain clear at the temperature of

a domestic refrigerator (5°C or 40°F).This criterion is met by soybean, rapeseed, olive and

sunflower oils. It is also met by maize oil, provided its traces of natural waxes have been

removed. So, all these oils can be regarded as interchangeable. Both groundnut and cotton-

seed oil tend to crystallise in the refrigerator, as does palm olein, which is the more liquid

fraction of palm oil.

While the above salad oils are interchangeable as regards technical performance, there are

still aspects of consumer choice.Thus olive oil is often prized for its special flavour charac-

teristics and commands a high price.There may be a preference for sunflower oil or maize

oil because they have long been promoted as being healthy, due to their high content of

the nutritionally essential linoleic acid.

Use in frying

The important use of oils and especially palm oil for frying will be discussed in Chapter 9.

At present, interchangeability of oils is limited in deep frying.This is likely to change in the

future due to the efforts of plant breeders. They are succeeding in producing oils with

reduced levels of the more unsaturated acids.

Extensive full-scale trials with a 'high oleic' sunflower oil (and low in linoleic acid) have

proved its good performance in potato crisps. Rapeseed and soybean oils of modified com-

position suitable for frying are now available in limited quantity.

Some snack food operations have already changed from palm olein to the high oleic sun-

flower oil despite its significantly higher price.This demonstrates the dynamic nature of the

competition between the different oils and of their interchangeability.

The reason for the decision to change is the perception that the more unsaturated sun-

flower oil is healthier. It is clearly important for the long term that research into creating a

palm oil low in saturates and high in unsaturates should be successful.

To take full advantage of the productivity of the oil palm, the world market has a clear

demand for two types of palm oil - firstly, the present type of palm oil, so valuable in the

production of consistent fats; but secondly an unsatisfied demand for a palm oil that is truly

competitive in its characteristics with the liquid vegetable oils.

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CHAPTER 2: TESTS OF QUALITY

Chapter 1 explained the chemistry of oils and fats, how this affects their use in foods, and

why the special characteristics of palm oil are valued.

In this chapter, we look at how the quality of vegetable oil is analysed – how quality of oil

is defined at the time of purchase in global trade, in view of the need to protect against

deliberate or accidental adulteration.

It describes how analysis methods are standardised and applied in determining ‘quality’,

which the dictionary defines as:

a. An inherent or distinguishing characteristic, a property; essential character or nature

b. Superiority of kind, degree or grade of excellence

In practical terms, is the oil what it is supposed to be and is it in good condition? Both these

aspects are defined by means of chemical analyses. For credibility, these must be carried out

by qualified analysts using standardised procedures.

STANDARD METHODS OF ANALYSIS

The process of standardisation is elaborate and is organised by national bodies such as the

British Standards Institute or American Oil Chemists Society, or international bodies like the

International Union of Pure and Applied Chemistry, International Standards Organisation,

or the Codex Alimentarius Commission set up under the United Nations.

A number of reputable laboratories volunteer to take part in the study of a method. A

‘recipe’ is circulated together with appropriate samples and the results are analysed statis-

tically. If not within acceptable limits of agreement, the details of the ‘recipe’ are discussed,

modified and further tests arranged. Eventually acceptable results are obtained and the

agreed method is given official status.

The Codex commission’s objectives are to agree on codes of practice and standards for

food commodities in order to facilitate international trade.Technical committees develop

the standards which are adopted at government level. Over 100 nations collaborate in the

Codex system and its standards carry a great deal of weight in commerce. Codex stan-

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dards deal with products in consumable condition and, therefore, mainly with refined oils.

Olive oil is an exception, since it is mainly used for direct consumption as crude oil.

CHEMICAL AND PHYSICAL DEFINITIONS OF IDENTITY

Source of oil

The first thing is to define the source of the oil. For example, soybean oil is derived from

seeds of the soybean (Glycine max); olive oil from the fruit flesh of the tree Olea europea,

and palm oil from the fruit flesh of Elaeis guineensis. Olive oil and palm oil are the only

major vegetable oils derived from fruit flesh. All others are extracted from seeds.

Iodine number

All oils contain a mixture of fatty acids, both saturated and unsaturated.The proportion of

unsaturated acids is a useful identity characteristic.The total number of unsaturated bonds

is readily measured by the Iodine Value – literally the number of grams of iodine needed to

react with the double bonds in 100gm of oil.

Being natural products, oils show some variation due to variety and growing conditions.

However, a range of Iodine Values normal for each oil can be established. For example,

Codex gives these ranges for three oils:

The Palm Oil Refiners Association of Malaysia (PORAM) has adopted the range for palm

oil products in its standard specifications.

Slip melting point

The melting point is a useful measure of the physical properties of oil. Fats are mixtures of

different glycerides, so they melt over a range of temperatures. A conventional method of

obtaining a clear-cut result is used. The ‘slip melting point’ is obtained by filling a capillary

tube with the sample in liquid form, crystallising it under precise cooling conditions, and

then determining the point at which the sample rises in the tube when heated in a water-

bath.The sample is not completely molten but a precise reproducible figure is obtained.

• For palm oil, extensive surveys by the Palm Oil Research Institute of Malaysia (now the

Malaysian Palm Oil Board) have established a range of 33-39°C, also used in PORAM

trading specifications.

• PORAM and Codex have adopted a slip melting point of 24°C or less for palm olein,

and 44°C or more for palm stearin. Codex also gives a point of 19.5°C or less for palm

super olein.

Composition of oils

Table 1 gives compositional data obtained by gas chromatography for typical samples of

palm oil and its fractions, as well as for soybean and olive oils. For simplicity only the main

fatty acid components are specified.

Chromatographic methods are also useful for analysing the minor components of oils. In

the Vitamin E group of substances (tocols), these consist of saturated tocopherols and

unsaturated tocotrienols (Table 2).

Sterol composition of oils also reveals differences useful for identification (Table 3).

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CRUDE PALM OIL (CPO) QUALITY

Different tests are needed to determine the condition of oils. Until the development of

Malaysian refining capacity, palm oil was mainly traded internationally as crude oil. Basic qual-

ity specifications of free fatty acids (ffa, maximum 5%) and moisture and impurities (maxi-

mum 0.25%) were adopted and are still used today for standard CPO.

The 5% ffa limit for standard CPO is higher than would be acceptable for other vegetable

oils.This is because the palm fruit contains a very active lipase (fat splitting) enzyme, which

rapidly breaks down the triglycerides to a mixture of ffa, monoglycerides and diglycerides.

The enzyme is released from the fruit cells when the fruit is over-ripe or when it is bruised.

In practice, the 1,000 or more fruitlets in a bunch do not all ripen simultaneously, so

it is likely that some will be over-ripe during harvesting; others will be bruised as the

bunch falls, and the lipase then becomes active. Fur ther bruising takes place in the var-

ious operations before the bunch is sterilised and the lipase is destroyed. If fresh fruit

is taken directly to the laboratory from the field, cooked and pressed immediately it

is possible to obtain oil with only 0.8% ffa, but this is not practicable on a manufac-

turing scale.

However, a special quality crude oil is offered by some producers. It is obtained by harvest-

ing somewhat early to minimise over-ripe fruit. Since oil synthesis in the fruit is very active

towards the end of ripening, some loss of yield results. Bruising during transport is avoided

by taking steriliser cages to the field for loading and sterilisation is carried out without delay.

Oil with a maximum ffa of 2.5% and minimal oxidation is produced and is easier to refine.

Moreover, lower ffa means also a lower content of mono- and di-glycerides which can

cause difficulty in fractionation.

Bleachability test

A pale near-white colour is regarded as an important characteristic of well-refined oil.The

bleachability of CPO in the refining process is largely determined by the extent of oxida-

tion, which leads to the formation of persistent coloured products.

European refiners use an empirically standardised bleaching test in the laboratory to esti-

mate the bleachability of CPO. Malaysian refiners have adopted a more science-based

procedure developed by PORIM, known as the Deterioration of Bleachability Index

(DOBI).

The DOBI test involves the measurement of the absorption of ultraviolet light by a solu-

tion of the oil at two different wavelengths:

• One (A) is a measure of the unchanged carotene present (carotene is easily destroyed

by oxygen).

• The other (B) measures the concentration of certain oxidation products of the fatty acids.

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The ratio of A to B is a sensitive indicator of the extent of oxidation. PORAM has adopt-

ed a minimum level of 2.30 as a standard.

Test for oxidation

Two measures of the oxidation level in crude oil are commonly used – Peroxide Value and

Anisidine Value.

The peroxide value is a direct measure of the amount of oxygen that has com-

bined at the double bonds of the fatty acids. In time these oxidised bonds are

broken, resulting in shor t chain volatile compounds and residues of oxidised glyc-

erides. These residues are measured by the Anisidine Value. A high figure is an

indication that oxidation has taken place in the past, and there has been a loss of

quality.

The two are sometimes combined – 2 x Peroxide + 1 x Anisidine is defined as the Totox

Value.While convenient, it entails some loss of information.

The full specifications for special quality CPO are given in Box 1.

REFINED PALM OIL QUALITY

Fully refined palm olein and palm oil are the main exports today. The PORAM trading spec-

ifications for refined palm oil are shown in Box 2.

The Codex Alimentarius has extensive specifications (Box 3), common to all vegetable oils

traded as refined oils. Each figure represents the maximum specification.

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CHAPTER 3: QUALITY DURING TRANSPORT

No commodity is improved by transport.The best that can be expected is that it should

arrive in unchanged condition.

Edible oils can suffer during transport in three ways:

• Oxidation through contact with air, particularly at higher temperatures

• Hydrolysis through the action of traces of water, catalysed by acidity or by enzymic

action from microbiological contaminants such as moulds or yeasts

• Foreign matter such as dirt or residues from previous cargoes

Most of the major vegetable oils are transported as crude oils at ambient temperature.

Malaysian palm oil is mainly transported in fully refined form. It needs to be kept warm to

prevent excessive crystallisation. Any loss of quality has to be rectified by a second refinery

treatment resulting in extra costs to the purchaser. Any chemical changes will occur faster

at temperatures above ambient.

In its early years, the Palm Oil Research Institute of Malaysia (PORIM, now the Malaysian

Palm Oil Board or MPOB) collected information on the extent and causes of quality

changes during transport.The transport chain usually involves a number of steps.

In some ports, unloading also involves the use of barges. At each stage the transfer involves

pumps,pipelines and tanks where contamination by previous cargoes or foreign matter can occur.

Each stage of the transport chain is under different management. In order to provide an

assurance of good practice, independent surveyors are employed to approve the condition

of the various facilities.

PORIM undertook to obtain first-hand information by sampling and analysing oil at various

stages of transport. Some results are summarised in Tables 1 to 3.

The shipment to New Zealand (Table 1) arrived in unchanged condition.The Pakistan ship-

ment showed some increase in acidity.The South Korea shipment showed appreciable oxi-

dation which had occurred partly during the journey and further during transfer by barge

at the port of arrival.

Samples were taken from several ships’ tanks during a voyage and analysed on board (Table

2). Measurements were made of the level of oxygen dissolved in the oil and of the perox-

ide value.

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The high iron content in the crude palm oil stearin catalysed oxidation of the oil, so that

the dissolved oxygen was nearly all used up and oxidation was appreciable. The refined

stearin had much lower iron content, and oxidation was quite moderate.A substantial pro-

portion of oxygen remained in solution.

Samples were drawn from a pipeline delivering oil into a shore tank at a foreign destina-

tion (Table 3).

Clearly the pipeline was not clean, but contained some water and a quantity of some

strongly coloured oil. From the rate of pumping it was calculated that the first 30-40 tonnes

of product were sub-standard.

As explained in Chapter 2, fully refined oil is expected to have a free fatty acid (ffa)

content below 0.10%. Evidence from a number of shipments has shown that it is a

case of the ‘the lower the better’. A follow-up study of 20 shipments showed that

when the acidity was 0.05 or less at loading, then 75% landed with ffa below 0.10%.

If the initial ffa was 0.05-0.10% (still within acceptable limits), only 20% landed with ffa

below 0.10%.

Inspection of some ships showed wide variation in conditions, from clean tanks with a per-

fect protective coating to those showing somewhat rusty surfaces. However clean the lat-

ter are, they catalyse oxidation reactions.

The overall conclusion was that the effect of transport varied, with significant effects on oil

quality in some instances.

PREVENTING LOSS OF QUALITY

Quality loss during transport is avoidable provided that exceptional care is taken in the

cleanliness and condition of the equipment, and that access to the air is prevented.The lat-

ter requires the provision of nitrogen gas throughout the transport chain from the refinery

to destination.

Storage tanks and ships’ tanks are flushed with nitrogen before being filled, and a nitrogen

atmosphere is maintained in the headspace above the oil. Gas is ‘sparged’ into the oil as it

is pumped through pipelines.This involves fitting an inlet tube so that nitrogen is forced into

the oil under pressure. Excellent results can be achieved, as seen in the examples in Tables

4 and 5.

Clearly nitrogen-blanketing largely prevented oxidation, but it also prevented any

increase in acidity.This is because the ‘sparging’ removes some of the low level of water

dissolved in the oil (no more than about 0.1%), which otherwise promotes some

hydrolysis.

Arrival of oils in perfect condition can be achieved, especially if the cargo is protected by

nitrogen throughout. However, nitrogen use involves extra costs and this has prevented its

use for the majority of cargoes. Still, the costs can be at least partly offset by avoiding any

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reprocessing to clean up the oil. At present only small quantities of oil are shipped with

nitrogen protection. The reputation of Malaysian palm oil is enhanced when such quality

maintenance is achieved, and the adoption of this handling procedure could form the basis

of a brand image that could not at present be matched elsewhere.

For speciality products shipped in smaller quantities, ISO tank containers may be used.

These are stainless steel tanks conforming to specifications laid down by the International

Standards Organisation (ISO).They hold about 21 tonnes of oil, have external heating coils,

top and bottom discharge points and are easily cleaned.Their use is more expensive, but

the likelihood of deterioration of the cargo is reduced.

SHIPPING CONTRACTS

The quality of Malaysian palm oil intended for export is controlled by government regula-

tions and monitored by the MPOB. Issues of quality are at the forefront of shipping con-

tracts and are dealt with in government and international regulations.

The Federation of Oils, Seeds and Fats Associations (FOSFA), based in London, prepares

formal shipping contracts. Clauses relate to the quality and specification of the oil and the

responsibility for cleanliness of the ship’s tank. The ship’s surveyor and the analytical

chemists are expected to be members of FOSFA.The ship’s master is required to com-

plete a certificate regarding the suitability of the tank, heating system and pipelines and

the cleaning procedures used. The three previous cargoes carried in the tank must be

specified.

The surveyor in turn completes a certificate of the cleanliness and suitability of the ship’s

tank. Loading and discharge procedures and the method of sampling for analysis are also

laid down. FOSFA provides training courses for the junior and middle management of sur-

veying companies.

The FOSFA operating procedures emphasise the control of temperatures of the

cargo.This is of par ticular importance for palm oil products. At ambient temperature,

palm oil would set solid and become vir tually impossible to unload. However, to keep

it totally liquid, a temperature would be required which would risk a serious level of

oxidation.

FOSFA requires the temperature to be controlled according to minimum and maximum

limits laid down by the International Association of Seed Crushers. Some crystallisation

occurs during the voyage, and controlled reheating is therefore applied some time before

discharge to raise the temperature by no more than 5°C/day, so that the oil arrives in a

homogenous liquid condition.

It is the surveyor’s responsibility to check that this condition has been reached at the time

of arrival and sampling. In the past, disputes have arisen due to inadequate reheating. In con-

sequence, the palm oil had partially fractionated into olein and stearin, and there were vari-

ations in composition of the oil throughout the tank.

In the USA, the National Institute of Oilseed Products (NIOP) carries out functions similar

to those of FOSFA. It prepares contracts, and its trading rules contain detailed requirements

regarding the quality of the shipping operations.

FOSFA also has recommendations for the handling temperatures for palm oil and palm ker-

nel oil products. Substantially, the same temperatures are advised by Codex Alimentarius

(Table 6).

The Palm Oil Refiners Association of Malaysia has a shipping contract for processed palm

oil, which is frequently used.The latest revision in 2002 uses the oil specification shown in

Chapter 2. Other items relating to quality are essentially the same as those given in the

FOSFA contract.

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CODE OF PRACTICE

The quality aspects of transport were discussed at an international oils and fats technical

conference in 1982. As a result a number of large industrial firms and some surveyors’

organisations collaborated with PORIM in preparing an advisory booklet on transport. It

covered design of pipework, tanks and heating systems, and operating procedures.

As a further step, the Codex Alimentarius Committee on oils and fats was requested to

put a Code of Practice for storage and transport into its programme of work.The adviso-

ry booklet was used as a starting point.

The question of possible contamination by previous cargoes required detailed study. Most

vegetable oil transport is from east to west, and ships carry a variety of chemical cargoes

on the return trip. Contamination of edible oils with traces of previous cargoes is undesir-

able and may be dangerous.

Discussion in the Codex Committee identified a number of questions to be answered, including:

a. which cargoes are toxic;

b. which products can be removed during a clean-up process of the oil;

c. which products are absorbed by the tank coatings and how can they be removed; and

d. what analytical methods are to be used.

FOSFA was asked to co-ordinate the extensive work programme required to provide

answers.

Document CAC/RCP 36 entitled ‘Recommended International Code of Practice for the

Storage and Transport of Edible Oils and Fats in Bulk’ was issued by Codex in 1987 and most

recently revised in 2005. It covers the design and operation of the facilities involved in the

transport chain. An important recommendation is that the condition of the equipment

involved in every transfer of the oil should be inspected by a qualified superintendent.

Previous cargoes

On the question of previous cargoes, it advised that the three previous cargoes carried in

a ship’s tank should be declared. Previous immediate cargoes are divided into those that

are banned and those that are acceptable. FOSFA adopts a similar ruling.

The NIOP rule is different. It only lists acceptable prior cargoes. A limited list is permitted

prior to the shipment of edible oil that may or may not be reprocessed before use, while

a somewhat longer list is allowed for oils that are intended for reprocessing.

These lists continue to be reviewed as necessary.

The European Community (EC) has also adopted a positive list of acceptable previous car-

goes, but believes that a negative list of banned immediate previous cargoes can cause con-

fusion in administering the system.

Oils that are not to be further processed must be carried in tanks that are:

a. of stainless steel, or lined with epoxy resin or similar coating; and

b. have been used for foodstuffs on the three previous voyages.

Where the oils are to be further processed, using tanks as in (a), only the immediate pre-

vious cargo must be foodstuff or from the permitted list. In due course an evaluation of the

acceptable list will be required by the EC’s technical committee.

The International Maritime Organisation (IMO) has a number of regulations which impact

indirectly on the quality of transport. It is chiefly concerned with preventing pollution of the

environment. Cargoes cause pollution if there is leakage due to an accident, and when tank

washings are discharged.

Vegetable oils are classified by IMO as hazardous, because they harm sea birds and marine

life.They must therefore be carried in vessels with double bottoms and in tanks of stainless

steel or suitable coatings. An exception is made for cargoes from destinations only served

by smaller, older vessels.

Recent experience indicates that contamination by previous chemical cargoes is rare.

Occasional quality problems occur due to the ingress of sea water, resulting in elevated ffa,

and also from overheating, resulting in some oxidation. Overheating may be due to a rapid

heating-up process before discharge or from heat passing from adjacent tanks.

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CHAPTER 4: BAKERY PRODUCTS

In the first three chapters, we discussed the chemical composition of fat, how its quality is

measured, and how we can ensure that exports reach their destination in good condition.

We will now consider the function of the fat in the food products.

Nutritionally fat is an efficient source of energy, usually measured in calories.A given amount

of fat yields nearly twice the calories produced by the same quantity of the other major

components of foods, the proteins and carbohydrate (starch and sugar).

Fats provide some essential dietary components, that is, those that cannot be synthesised

in the body.These are Vitamins A and E, pro-Vitamin D – which is converted into Vitamin

D in the body – and the fatty acids linoleic (2 double bonds) and linolenic (3 double bonds).

A further function is to contribute to the flavour of the foods, both directly – for example

in the use of butter or olive oil – and indirectly, as a result of chemical changes and interac-

tion with other ingredients during cooking. Finally of particular interest to the food technol-

ogist is the part that fat plays in developing the structure of various food products.This will

be discussed, first in relation to bakery products.

AIR CONTENT AND THE ROLE OF FAT

We do not generally appreciate that air is an important component of many foods. For

example a loaf of white bread contains about 60% of air by volume. Without the air you

would have a hard flat biscuit, the unleavened bread of the Bible.

Before discussing the different types of bakery products we need to understand the nature

of wheat flour, the major ingredient (Table 2).

The protein content of wheat varies from 8-14% or more, depending on variety and grow-

ing conditions. Low protein ‘weak’ flours are used for cakes, and for most pastry and biscuit

types. High protein ‘strong’ flours are needed for bread and puff pastry products.

The most interesting component of the wheat flour protein is gluten. During mixing of

dough it hydrates and, as mixing continues, it becomes elastic and stretches into thin fila-

ments.When a product is baked the gluten dries, denatures and becomes tough.

In cakes, we do not want a tough chewy texture, and the weak flour may be treated to

reduce the activity of the gluten further.

Cakes

Our first example is a Madeira cake.The fat used in cake manufacture performs two impor-

tant functions. Firstly it enables air to be incorporated in the batter, and secondly it con-

tributes to the tender ‘short’ eating quality of the baked cake. Good aerating properties

require a sufficient liquid oil content to enable air bubbles to be formed, and also the pres-

ence of solids in the form of small crystals (Figure 1).

In a typical two-stage mixing process for a Madeira cake, the fat is first mixed thoroughly

with about half of the flour and beaten to incorporate air. A Hobart-type of mixer fitted

with a whisk type mixing arm is usually used both in the home and in the industry.The mix

is aerated to 40-45% air. Examination under the microscope shows that the air bubbles are

surrounded by fat.

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31

Next, the remainder of the flour and the aqueous ingredients are added and mixed.The air

content of the batter has now been diluted to about 15%. Figure 1 is an electron micro-

graph of an air bubble in cake batter, magnified about 5,000 times. We are looking at the

internal surface of the bubble, which has been cut in half.The surface consists of liquid oil

and looks smooth: however it shows a number of sharp lines.These are edges of small fat

crystals lying on the exterior surface of the bubble.The diagram in Figure 2 shows the need

for small crystals that line the air cells efficiently. Large crystals would not be effective in

containing and stabilising the air cells (Figure 2).

Small crystals are ensured both by correct formulation of the fat blend and by its pro-

cessing. A good shortening requires the fat to be in the ‘beta prime’ polymorphic

form, in contrast to the large crystals of the ‘beta’ form. The difference is made clear

under the optical microscope, using polarised light to show up the crystals (Figures 3

and 4).

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33

The aspects of polymorphism of fats will be discussed in a later chapter.The word derives

from the Greek for ‘many shapes’.

Coming back to our well aerated cake batter, it is now ready for the oven. When

baking star ts and the temperature rises, water vapour is generated and goes into

the existing air cells, as does the carbon dioxide from the baking powder. The air

cells become larger. At this stage they are still surrounded by fat. As the tempera-

ture reaches about 40ºC the fat melts and the air bubbles move into the aqueous

phase. Here the viscosity is increasing due to swelling and gelling of the starch, so

the air bubbles are retained. Eventually the egg protein sets and the cake structure

is fixed.

Measurements under the microscope give air bubbles of an average diameter of 20 microns

(1 micron = 1 millionth of a metre) in the batter ; and in the baked cake, of 110 microns.

So, they are still very small.The final air content is 65%. Figure 5 shows a slice of Madeira

cake with its very fine air bubble structure.

Three tested formulae for bakery shortenings are given in Table 3.These fats have proved

successful both in cakes and in pastry products.

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35

Puff pastry

Its distinctive character is derived from thin layers of a crisp pastry separated by large air

spaces. Dough is made using a ‘strong’ flour of high protein content and a small proportion

of fat, and is formed into a flat rectangle. A layer of special pastry margarine is then placed

on half of the dough area.The other half of the dough is folded over and the parcel is pro-

gressively rolled down in thickness through a pair of pastry rollers.The dough is folded over

once, turned through a right angle and rolled again.

A complete sequence of rolling, folding and turning results finally in many thin layers

of dough inter-leaved with layers of fat. This pastry is baked in a very hot oven. The

steam generated within the dough is retained by the layers of fat and can only escape

after it has lifted the thin layers apar t. They then cook to give an attractive crispy

nature.

The properties of the fat must be rather special. It is essentially important that the fat

does not mix into the dough during the rolling process. It must therefore be very

resistant to work-softening. A high degree of plasticity and a somewhat high melting

point is required. Palm oil and palm stearin are suitable components for pastry mar-

garine.

Figure 6 shows the effects of correct and incorrect processing of the dough. If there are

too few ‘turns’, not enough layers are formed. If there are too many, the fat has worked

into the dough. Figure 7 shows puff pastry samples prepared in a comparison of two

fats.

Formulae for a puff pastry fat

Successful formulae based on hydrogenated palm oil are in use but have a content of the

undesirable trans fats. It should be possible to use palm stearin instead, for a trans-free

product.

Table 4 shows tested formulae.The third column shows the unusually high melting point of

fat that is required to get good performance in a hot climate. Column 4 gives a softer blend,

which is suitable for the preparation of flaky pastry products.

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Short pastry and biscuits

The major components of these products are flour, fat and sugar in varying proportions,

together with a small proportion of water. Minor components such as dried fruit or choco-

late chips are added to biscuits to give a particular character.The eating properties – the

texture – of biscuits and pastry vary over a wide range (Figure 8).

37

Think for instance of a ginger biscuit with a crisp tough character and, at the other extreme,

a shortbread biscuit which has a crumbly ‘dissolve in the mouth’ character. In most prod-

ucts the air spaces play a minor role in the structure.

38

The different textures are obtained by controlling the extent to which the gluten is enabled

to develop. By using a high proportion of fat and ensuring that the flour particles are well

coated with fat, the access of water to gluten can be minimised. A very short, melt-in-the-

mouth texture is obtained, as in Scotch shortbread. With a lower proportion of fat and

more intense mixing, the gluten is developed to some extent and a somewhat tougher or

crispier texture achieved.

The characteristics of fat are also important. If liquid oil is used, it will fail to coat the flour

particles efficiently because it has a tendency to form droplets. A fat blend must have small

crystals and a smooth easily spreadable texture. Palm oil is very effective as a major com-

ponent of such a blend.

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CHAPTER 5: AERATED DAIRY PRODUCTS

Dairy and vegetable oil based creams can be whisked or whipped in such a way that at

least an equal volume of air is incorporated. As a result the products have a more attrac-

tive texture and mouth-feel.

Whipped cream

Whole milk contains about 4% of fat which is present as small globules averaging 7-8

microns in diameter. Each globule is enclosed by a coating or membrane of milk protein.

Cream is traditionally made by skimming the upper layer from milk that has been allowed

to stand. In effect the fatty emulsion phase has been concentrated.

In modern practice this concentration is achieved efficiently in a centrifuge and can be taken

to the stage of single cream (18% fat) or double cream (about 42% fat). If the cream is agi-

tated sufficiently the fat globules impact on each other and stick together. In due course the

fatty phase becomes more or less continuous and butter is obtained.

If the cream is agitated in such a way that air is incorporated, then it is possible to form a

rigid structure containing about 50% by volume of air. The continuous phase which gives

the product stability is the fat that has coalesced during the agitation. If homogenised cream

is agitated in the same way, a whipped cream of similar air content is obtained. During

homogenisation the individual fat globules are broken down to a size of about 1 micron.

During the aerating process the small globules cluster together and impart sufficient

strength to the air-cell walls to produce a stiff aerated cream. The relatively low melting

point of butterfat means that the aerated cream has limited stability up to about 25ºC in

the European summer and in warmer climates.

Imitation cream

Imitation creams are made by homogenising an emulsion of vegetable fat in skimmed milk

with added sugar. Their behaviour on aeration is then very similar to that described for

homogenised dairy cream. By an appropriate selection of the fat used, aerated structures

of greater stability than real creams can be produced.

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A very suitable fat for ambient temperatures up to 25ºC is hardened palm kernel oil

(HPKO) with melting point 35ºC and Iodine Value 1.0. For higher ambient temperatures, a

formula of particular interest consists of fully hydrogenated palm kernel oil together with

palm stearin (Iodine Value 19). In this, 66 parts of the HPKO and 34 parts of the palm

stearin are interesterified.This process causes all the fatty acids to change places in a ran-

dom manner and alters the melting properties of the mixture.The whipped cream made

using this fat was stable at a temperature of 35ºC. For even higher temperatures an

increase of a few percent of the stearin proportion can be used.

Curves for the solid fat content of HPKO and of the blend are shown in Figure 1.The shad-

ed area of increased solids in the blend is responsible for its better stability at the higher

ambient temperature, but without affecting the mouth-feel.

41

The structure of the cream is shown in an electron micrograph for a cross-section of an

air bubble (Figure 2).The air cell has a continuous surface layer of fat which is then lined by

numerous intact fat globules. The ‘stand up’ strength of the whipped cream is mainly

dependent on the fat globules.

ICE CREAM

Ice cream is made with dairy cream or an emulsion of vegetable fat with skimmed milk.

Table 1 compares a typical composition of ice cream with that of milk.

42

There is considerable flexibility in the formulation of ice cream.Thus luxury grades contain-

ing 15% or more of fat and also reduced fat content products have been marketed. In the

latter type of product, the desired creaminess effect on the palate can be obtained by

changes in the thickeners used.

Ice cream is also a good vehicle for introducing nutritional supplements such as vegetable

sterols which lower blood cholesterol levels, or minerals such as calcium and magnesium

which strengthen bones.

Processing steps in developing ice cream structure

1. Prepare the mix.

2. Pasteurise it to destroy harmful bacteria.

3. Homogenise the hot mix to break up the fat into small globules (0.04-3 microns)

and make the emulsion.

4. Cool the emulsion to 4ºC and store for 2-3 hours or more to allow it to settle

down. Time is needed for the fat to partly crystallise and the milk proteins to coat

the surface of the fat globules.

5. Freeze and aerate the mix

The freezing takes place in a scraped surface heat exchanger. It is the most dynamic stage

in the processing and results in the development of the final structure.The following events

occur in the freezer:

• An increase occurs in the collision frequency of the fat globules due to mechanical

agitation.

• Ice crystals force the fat globules into the decreasing spaces occupied by unfrozen

material, and probably cause shape distortion.The development of ice crystals and

the mechanical action in the freezer cause some breakdown of the emulsion.

• Air is introduced into the mix and dispersed into fine bubbles by the intense agitation.

The partial destabilisation of the emulsion in the freezer is now generally accepted as

important in the formation of a stable ice cream structure.

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On leaving the freezer about 50% of the water in the mix has turned to ice and the struc-

ture is fully formed.The ice cream is filled into packages, hardened in a cold store at -30ºC

and is then ready for distribution. It is generally held at -17ºC or -18ºC until retailed.

Structure of ice cream

The final structure is similar to that obtained for whipped cream; stability is provided part-

ly by fat globules lining the air cells but also by the ice in the continuous phase.

Figure 3 shows an electron micrograph of ice cream.The frozen sample has been cut across

and what we see is half of an air bubble. It is lit from above, so that the top part is in shad-

ow, the lower part being brightly lit.The surface is smooth, consisting of a layer of liquid oil.

The ‘bumps’ in the surface are small fat globules (A) sitting on the outside of the oil layer.

An ice crystal (B) can be seen protruding into the air bubble.The scale is indicated by the

one micron bar. The air bubble is about 5 microns in diameter, while fat globules are 0.5

microns or smaller.

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The layer of liquid oil forming the surface of the air bubble is derived from fat globules

which were broken open during the intense agitation in the freezer. Figure 4 shows such

broken fat globules.

The dimension of some components of ice cream, as measured under the optical and the

electron microscope, are shown in Table 2.

By the time the product has reached the refrigerator at -18ºC, about 85% of the water is

present as ice and it might be thought that the ice alone would be sufficient to maintain

the structure. However, this is not the case.

45

If an ice cream is made with liquid vegetable oil, a different picture is seen in the electron

microscope (Figure 5).The air bubble is not lined by intact fat globules, and none can be

seen in between the air cells.

The frozen ice cream soon starts to lose air during storage, shrinks in the container and

becomes unattractive. Evidently a good ice cream fat needs to have a solid fat content dur-

ing processing.Table 3 gives the proportion of liquid oil remaining of some satisfactory fats

at +5ºC and -5ºC, the temperature before and after freezing.

CHAPTER 6: BUTTER ALTERNATIVES

It is no exaggeration to say that the invention and subsequent widespread manufacture

of margarine initiated the development of the oils and fats processing industry as we

know it.

Up to the 19th century the fats available for food use in North Europe were solely those

produced in the farm yard. Contemporary English cookery books referred only to butter,

beef fat and lard.The industry consisted of the rendering of carcase fats and a limited frac-

tionation of beef fat to produce stearin for candles.1

In Mediterranean Europe, olive oil had been the main edible oil in use for some 5,000 years.

Rapeseed was crushed for oil in North Europe, but was only suitable for inedible applica-

tions such as lamp oil. Palm oil, imported in small amounts from West Africa since 1780,

was likewise of inedible quality.

The Industrial Revolution in Europe resulted in the movement of the population from

the countryside into the cities, resulting in shortages of food from time to time. In

1865 there was a shortage of butter in Paris and in supplies to the army.This led the

emperor Napoleon III to offer a substantial prize for the invention of a suitable but-

ter substitute.

French pharmacist and inventor Hyppolyte Mege Mouries took up the challenge. In his

experiments, already in hand in 1867, he noticed that cows starved of food continued to

produce milk. Although reduced in volume, the milk still contained fat. He argued that the

cow was able, by means of enzymes in the udder, to transform its high-melting body fats

into the softer butterfat.

He took carefully rendered beef fat, allowed it to crystallise at about 30ºC and separated

the still liquid portion.This was called ‘oleo-margarine’.The name was taken from oleic acid

from the Greek word for ‘pearl’, referring to the lustrous appearance of the fat when solid.

46

1 Candles were a valuable commodity in the home, without these, activity in the long winter evenings was verylimited. Coalmine owners supplied candles to underground workers and had to colour them green to prevent theft.

47

The oleo-margarine was melted and mixed with 30-35% skimmed milk, to which 0.1% of

minced cow’s udder was added.The whole was stirred for 2-3 hours at the body temper-

ature of the cow.The resulting emulsion was churned as if it was real cream.Then chilled

water was added to crystallise the fat. Free water was removed and the fat kneaded until

no more water separated. During the kneading some salt was added. The end product

looked like butter.

The addition of cow’s udder was thought to help the emulsification, but it was soon aban-

doned. Mege Mouries won the prize: he patented his process in France, then in the UK in

1869 and in the USA in 1873. He started manufacture in Poissy near Paris, but the enter-

prise did not succeed. However the process was licensed to Jurgens in Holland in 1871 and

production also soon started in Germany, Austria, Scandinavia and the USA.

The product proved popular, but soon local supplies of beef fat ran out. Imports from the

USA and Argentina were used. Already in the 1870s some patents described the use of

10-20% of vegetable oils. Initially, carefully prepared unrefined groundnut oil and coconut oil

were used but, as the refining process was developed, other vegetable oils became suitable.

Hydrogenation

The invention of hydrogenation of unsaturated bonds and its development for edible oils

early in the 20th century widened the ingredients available. Any liquid oil could be hydro-

genated, in other words hardened, to a chosen extent. So, the industry was no longer

dependent on beef fat to provide the structure of margarine.

New ingredients became available, in particular whale oil and fish oils, both of which need-

ed partial hydrogenation. Although palm oil had been imported for over 100 years from

West Africa it was of very high acidity and suitable only for industrial uses. Some palm oil

of superior quality then became available from Africa that was suitable for the edible fats

industry. A reliable quality of palm oil has been available from Malaysia and Indonesia since

the 1950s.

The dairy industry in many countries reacted strongly to the competition from margarine

and lobbied for restrictive regulation. For example, in Germany, butter and margarine could

not be sold on the same premises. Retailers had to erect partition walls and doors to sat-

isfy the letter of the law.

In Italy a campaign by agricultural organisations led to a ban on the manufacture of mar-

garine for household use in 1934, followed by a complete ban in 1937. This was relaxed

after the war, but restrictive controls remained until food laws were unified in the European

Union.

A number of countries required the addition of sesame oil as a ‘marker’. A small percent-

age was added and could be easily detected in the laboratory, thus preventing margarine

from being mixed with butter. Elsewhere a small amount of starch was added for the same

purpose.

Developments in the USA

The industry in the USA had a par ticularly hard struggle under both federal and state

restrictions. Margarine manufacture star ted in 1874; at this time butter was mainly

made on the farm, packed and distributed in small wooden barrels to be portioned

out and wrapped by the retailer. Margarine was handled in the same way, and it was

easy to mix both in the shop. Initial attempts to regulate the trade at state level were

ineffective. Control was achieved under federal law in 1886 requiring proper labelling,

introducing a tax on margarine and the purchase of licences by manufacturers and

dealers.

Later regulations required margarine to be packed and labelled in 1-1b blocks in the facto-

ry. In 1902 a tax of 10 cents/lb was imposed on margarine coloured yellow, making it more

expensive than butter at times.Attempts to colour it with natural palm oil were disallowed.

For a long time margarine could be bought white, with a sachet of colour which the con-

sumer had to knead into the block. Additional 10-cent taxes were imposed at state level.

Examples of state and federal tax stamps are shown in Figure 1.

During World War II shortages lead to greater use of margarine and a generally favourable

consumer attitude.As a result, federal taxes and licence fees were removed in 1950. Today

the dairy and margarine industries coexist peacefully in the USA and elsewhere.

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NUTRITIONAL CONSIDERATIONS

Margarine was accepted as a nutritionally satisfactory basic food. Early regulations con-

trolled the minimum fat and maximum water content and allowed fortification with

Vitamins A and D. In the 1950s concerns over heart disease led to advice to reduce the

intake of cholesterol, present in animal products, and therefore there was a move towards

vegetable oil formulations.

An emphasis developed on the use of ingredients containing the essential linoleic and

linolenic acid which cannot be synthesised in the body.They are the precursors for longer

chain acids of 20 carbons with 5 double bonds and 22 carbons with 6 double bonds. These

are used in the body to make essential hormones and brain components.

Linolenic acid is present in rapeseed and soybean oils, which can easily be used in mar-

garines and spreads.The 20 and 22 carbon acids are present in fish oils.They are very sen-

sitive to oxidation and need special handling if they are to be used.

Trans fatty acids

Partly hydrogenated oils were generally used, having a significant content of trans fatty acids

(trans fats).Their adverse health effects are now universally accepted.The position is well

stated by Dr A Aro, an experienced researcher who reviewed the results of many studies:

“A high intake [of trans fats] affects the ratio between LDL- and HDL- cholesterol in a way

that is unfavourable compared with all other fatty acids.”

LDL-cholesterol is the ‘bad’ compound associated with an increase in the risk of heart dis-

ease, whereas HDL-cholesterol is the ‘good’ one that removes excess cholesterol.

The body of evidence against trans fats has grown. Further studies have indicated that they

raise the levels of triglycerides and the tendency towards inflammation; both are risk fac-

tors in heart disease.

On the regulatory front, the USA has implemented since January 2006 new labelling reg-

ulations requiring the trans fats content in food products to be declared. The consumer

now understands that trans fats are undesirable, thereby inducing strong moves by manu-

facturers to reduce the use of hydrogenated oils.

The New York City government has gone further to tell restaurants and food suppliers to

reduce trans fats to the low level of 0.5g/serving.This has had a knock-on effect, since the

wholesale suppliers to the restaurants have had to reformulate their products, and in prac-

tice would then use the new formulae for all their manufacture. Other local authorities in

the USA may follow suit.

In Denmark, legislation has restricted the trans fats content of all food oils and fats to below

2% since 2003; no adverse effect has been noted on the quality of food products.

In Canada it became mandatory to give the trans fats content on product labels in

December 2005. A government task force recommended that regulations should be made

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51

by 2008 but, in June 2007, the government decided instead to request industry to reduce

the trans fats content voluntarily to the lowest possible levels within two years, to avoid leg-

islation being imposed.

A consequence of these moves against hydrogenated fats is that the use of palm oil prod-

ucts continues to increase, to provide the required solid fat content.

Reduced-fat spreads

Another nutritional problem led to the development of reduced-fat spreads to meet the

need to reduce calorie intake to combat the rise in obesity. These products cannot be

called ‘margarine’ but need to behave and look like it. A part of the fat content is replaced

by water, and in order to maintain the desired consistency, small amounts of thickening

agent dissolved in water are used.The consumer can then apply a generously thick layer to

a slice of bread, but with fewer calories.

Vegetable sterols

The most recent development with a nutritional objective is the enrichment of

spreads with vegetable sterols. It has been known for many years that the consump-

tion of vegetable sterols reduces the absorption of dietary cholesterol, and there-

fore reduces blood cholesterol level (which is a risk factor for hear t disease if it is

elevated).

The vegetable oils consumed normally contain about 0.3gm sterol, but this is not sufficient

to be useful. An additional daily intake of about 2gm reduces blood cholesterol by around

10%. Products containing vegetable sterols are now readily available.

‘Conjugated’ linoleic acid (CLA)

An interesting recent finding is that one particular type of trans fats actually has beneficial

health effect. CLA has one of its double bonds in the ‘cis’ and the second in the ‘trans’ posi-

tion. It is naturally present in small proportions in animal fats, which are nowadays con-

sumed in lesser amounts. CLA inhibits tumour growth and the risk of blocked arteries, and

tends to reduce body fat. Canola oil has been interesterified with CLA and used at the

Malaysian Palm Oil Board (MPOB) to prepare margarine on a pilot-plant scale. It contains

over 10% CLA.

FORMULATION OF FAT BLENDS

How does the food technologist set about formulating products such as margarine or bak-

ery fat? Two basic properties of the finished product are important – the proportion of solid

fat present at temperatures relevant to its use: and the shape and size of the crystalline solids.

Individual triglycerides may have melting points as high as 60ºC or as low as -10ºC. Any

natural fat is a mixture of a number of triglycerides and will contain a percentage of solid

glycerides at intermediate temperatures. This percentage can be readily measured

because the solid glycerides respond to a magnetic field differently from the liquid. By

measuring at a range of temperatures we can construct a curve of solid fat percentage

against temperature.

Palm oil

We need to look at palm oil and palm kernel oil in more detail. Palm oil is readily fractioned

into a hard portion (stearin) and a more liquid portion (olein).The process involves hold-

ing the oil at a chosen temperature to allow partial crystallisation to occur, then separating

the olein, usually in a filter press. Depending on process conditions, the properties of the

fractions can be varied.

Curves for the solid fat content (SFC) of palm oil and its products are shown in Figure 2

and compared with butterfat.

The curves for butterfat and palm oil are remarkably close, but there is one important point

of difference. At body temperature (36-37ºC), butterfat is completely molten, but palm oil

has 4-5% solids.This means that it may leave a greasy feel on the palate. Below 15ºC, but-

terfat becomes rather hard. As we know, butter taken straight from the refrigerator is not

easy to spread.What is clear from the curves is that palm oil is suitable as a major compo-

nent of margarine formulae.

The two curves for palm stearin (2 and 3) show that a variety of properties can be

obtained, enabling the technologist to choose the most suitable. Curve 4 shows a standard

palm olein with appreciable solid content at 15ºC and 20ºC, unlike unsaturated vegetable

oils such as soybean and rapeseed oils.To obtain improved properties, a double fractiona-

tion process is required (Curve 5), but it makes this olein more expensive.

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The SFC curves for palm kernel oil (PKO) products are shown in Figure 3. PKO has high

solid content at 15ºC and 20ºC and is a firm solid, but above 20ºC it melts rapidly. This

behaviour is even more pronounced in palm kernel stearin, and leads to some special appli-

cations at high value, which are described in Chapter 7.

PKO is a valuable ingredient in margarine blends, in particular when palm oil is also used.

Mixtures of palm oil with PKO have some difficulty in crystallising because the diverse chain

length fatty acids do not fit in together easily. Figure 3 shows this effect in terms of the liq-

uid oil content. A mixture of 60% palm oil and 40% PKO is still liquid at temperatures

where each of the components on its own would be solid.

When used in a margarine formula, such mixtures improve the melting characteristics in

the mouth, bringing it closer to the behaviour of butter.The mixture is technically described

as ‘eutectic’, derived from the Greek, meaning ‘good melting’.

An economically major ingredient for margarine and spreads is obtained by interesteri-

fying palm stearin (60%) with palm kernel olein (PKOL, 40%). The stearin component

provides the necessary firmness in the end product, while the PKOL ensures good melt-

in-the-mouth properties. The margarine will have a content of short and medium chain

fatty acids similar to those in butter.

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55

It is clear that palm oil – which is free of trans fats – offers a direct way of obtaining the

solid content needed to give margarine its consistency. A second way is to prepare fully

hydrogenated oil, such as soybean or rapeseed, and interesterifying it with a proportion of

liquid oil.This is normally more expensive.

WHAT IS THE RIGHT CONSISTENCY?

The desired consistency of margarines and spreads can be defined as being spreadable at

the temperature of use. Margarines have a physical behaviour in between that of liquids –

which flow when poured – and solids, which move as a whole when pushed.

They have an internal structure that consists of a network of very small crystals of the solid

triglycerides.This three-dimensional network holds the liquid oil component and also the

emulsified aqueous phase.The network is rigid enough so that the product looks solid but

is easily disturbed when ‘pushed’.Then the liquid component takes over, and the margarine

flows until the pushing stops.

‘Spreadability’ means we can cut a portion of margarine from a block or out of a tub, apply

it to a slice of bread and spread it. Physicists define the force needed to make the mar-

garine flow as ‘yield value’.This can be measured with simple equipment and used to com-

pare the spreadability of different products. The spreadability changes quite rapidly with

temperature. It may be said that the spreadability of butter is not ideal. It is good between

15ºC and 25ºC, but outside this range is either too hard or too soft in a warm climate.The

margarine manufacturer can improve this.

Experience shows that a SFC between about 15% and 35% is suitable. See Figure 5 for SFC

curves of various products.

A second factor is that the solid fat must be in small crystals. As we have seen in relation

to shortenings, this requires the beta prime polymorphic form (Figure 3, Chapter 4).

Problems arose in Canada when margarine was formulated with hydrogenated rapeseed

oil, the local produce. It transformed during storage to the beta form, giving an unsatisfac-

tory appearance and a gritty feel on the palate (Figure 6).

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57

The reason for the transformation is that the canola oil contains almost solely fatty acids of

18 carbon atoms. When the margarine was reformulated using a proportion of palm oil

(with palmitic acid of 16 carbon atoms) the change to the beta form was made difficult due

to the diversity of chain lengths, and the product was stable in the prime form.

HISTORIC MARGARINE FORMULAE

Table 1 gives a number of published formulae.Apart from the first, the formulae all contain

trans fats from the hydrogenated component.

Experimental formulae that have satisfactory characteristics and are free of trans fats have

been developed in the laboratories of MPOB (Table 2).

58

While manufacturers do not generally reveal the blend formulae in use, analyses show that

today, margarines in Europe are substantially free of trans fats and that there have been big

reductions also in the USA. At the same time, their imports of palm oil and stearin have

increased.

Improved margarine processing

Mege Mouries’ original process was soon improved.The margarine emulsion was pumped

in a thin layer onto a rotating drum, which was chilled internally with ice water or a refrig-

erant. Crystallisation in the desired small crystals was initiated.The partly crystallised mass

was scraped off into an open trough fitted into a rotating shaft fitted with beater arms.The

fully crystallised fat was rested for a time and packed.

This processing is today essentially unaltered, but now it is carried out within a scraped sur-

face heat exchanger (Figure 7) and then a second cylinder – the ‘worker unit’ – where fat

is intensely mixed (Figures 8 and 9). After a period in a resting tube, the product is ready

for packing; today, usually into 250gm or 500gm packs or plastic containers.

Table 3 gives prices of products on the shelves of a London supermarket.The second col-

umn gives the price calculated for the fat component (i.e. the nutritional element).

59

60

Production and consumption

Margarine production has shown continuous growth, with some increase in rate during and

after World War I. During World War II, the high quality of the product was recognised and

when rationing was relaxed, production went up. The slower increase from about 1960

was due to the lower fat content of the increasing market for reduced fat spreads. Figure

10 shows world production data for margarines and spreads.

It may be noted that Denmark has the highest per capita consumption of margarines and

spreads. This is because its important dairy industry exports much of the production.

Consumption in some Western countries is listed in Table 4.

VANASPATI

In the Indian subcontinent, butter very quickly develops an off-flavour mainly due to

hydrolytic breakdown of the glycerides at the high ambient temperature. It has therefore

been traditional to market ‘butterfat ghee’. This is made by melting butter and boiling off

the water layer. A desirable flavour develops.

61

In 1930 Hindustan Lever developed vanaspati as a vegetable oil-based alternative.

In order to find acceptance among consumers, some butter flavour was added and

the appearance of butterfat ghee was imitated. When the melted butterfat cools

slowly, it crystallises in rather coarse grains, up to 1-2mm across, with a little free oil

remaining.

62

Figure 11 is a photograph of the crystals in a thin layer of vanaspati. This appearance is

regarded as important by the consumer and therefore had to be achieved in the alterna-

tive product.

Government regulations initially required the melting point to be no higher than 37-38ºC but

subsequently the range was widened to 41ºC. A suitable product was obtained by partial

hydrogenation directed towards the production of trans fats in preference to saturated acids.

Similar products are used in the Middle East and Egypt, and by expatriate Indian popula-

tions in other countries. Most of these countries rely on imported oils for a large part of

their consumption. The market for vanaspati in Pakistan is 1.7 million tonnes, while the

world market was estimated at 5-6 million tonnes in 2009.

63

Formulation

Palm oil has the desired melting point for vanaspati. However, when crystallised slowly, it

forms small crystals and a high proportion of liquid oil. A better appearance can be

obtained with a blend containing some hydrogenated oil, or by interesterification. Some sat-

isfactory experimental formulae with zero trans fats are shown in Table 5.

In the 1980s, when vanaspati was largely based on hydrogenated vegetable oils, the trans

fats content was high with a figure of 53% for India, more than 50% for Iran and 27% for

Pakistan. However, as palm oil became available, a lower trans fats value of 3.7% was report-

ed in Pakistan.

More recently, as consciousness of the adverse effects of trans fats spread, Iran introduced

a limit of 20%, to be reduced further with time. In India, adverse comments appeared in

the press in April 2009 about analyses of products in the market with 23-24% trans fats.

At present the formulations used in Pakistan are varied. Due to the high summer temper-

atures a firmer product is required (Table 6).

64

The processing of vanaspati is very simple.The warm blends are filled into large tins, typi-

cally 28lb, and placed in a temperature controlled store at 21-22ºC until cold.

65

CHAPTER 7: THE LAURIC OILS

The oil palm is the only crop yielding two different types of oil.The yield of palm kernel oil

(PKO) is about 10% of the oil derived from the flesh.The most interesting feature of the

two oils is the substantially different make-up of the fatty acids.

Palm oil, like most vegetable oils, contains mainly fatty acids with 16 or 18 carbon atoms.

PKO typically contains 48% lauric acid with only 12 carbon atoms and another 9-10% of

fatty acids with shorter chain length.The only similar oil available commercially is coconut

oil.These two are often described as lauric oils.

Figure 1 shows how the production and export of the two oils have developed over 20

years. There is a striking difference. The availability of PKO has grown in line with the

increase in palm oil supplies. The volume of coconut oil has, however, remained about

static.

66

The oil palm and coconut palm are members of a large family of some 3,000 species.

Several hundred of them are native to the Amazon basin in South America, and some have

been exploited by the native populations for their oil content.

Chemical analyses of kernel oils from a number of these species show that they are all lau-

ric oils, and this is probably true of all the palm family. Attempts to commercialise some of

these kernel oils have failed. The exception is babassu oil – a few thousand tonnes have

occasionally appeared in the market.

The babassu is a large palm of the Amazon forest and it grows in dense natural stands.The

kernel forms only 10% of the fruit, so it must be extracted on site from the nut for

economies of transport. However, it is encased in a thick and extremely hard shell, which

presents a technical challenge. It has been estimated that 1-2 million tonnes of oil per year

are not being utilised. A commercial evaluation of the oil has indicated that its properties

are intermediate between PKO and coconut oil and that it would serve similar applications.

Table 1 shows the fatty acid composition of the lauric oils – note the contrast with palm oil.

Oleochemical demand

The content of medium and short chain length fatty acids renders the lauric oils of great

interest to the oleochemical industry.Worldwide, it uses up to half of the lauric oil supplies.

67

The demand from both the food and oleochemical industries means that lauric oils usual-

ly fetch a premium over other vegetable oils.The rapid development of the oleochemical

industry in Malaysia is indirectly illustrated by figures for domestic disappearance of 53,000

tonnes in 1986, rising to 1.41million tonnes in 2009, most of which was converted into

chemical products for export.

Probably the biggest chemical use of lauric oils is in soap making, as has been prac-

tised since the time of the ancient Egyptians. A good soap formula consists of 75-

80% tallow, palm oil or palm stearin and 20-25% lauric oil. Functionally, the shor ter

chain fatty acids impar t good foaming while the long chain fatty acids give the foam

persistence. The foam suspends par ticles of dir t and is impor tant for a good cleans-

ing action.

Other technical uses require, as a first step, the formation of fatty acid compounds such as

esters, fatty alcohols, a variety of nitrogen compounds and metal soaps. Further chemical

modification is often required to reach end products with a long list of applications in a vari-

ety of industries.The list includes personal care products, surface active agents, anionic and

nonionic detergents, fabric softeners, lubricants, mineral processing aids and corrosion

inhibitors.

FOOD USES OF PKOThe solid fat content curves for PKO products are shown in Figure 3, Chapter 6. The steep

melting curve of PKO in comparison with palm oil should be noted. This is even more

marked in palm kernel stearin (PKSt).

When eaten, foods with a high content of PKO give rise to a pleasant cooling sen-

sation on the tongue due to heat being rapidly abstracted as the oil melts. This may

be noted in biscuits with a cream filling, in whipped cream and some confectionary

products.

Margarines and spreads

Another feature of PKO behaviour of particular value in margarine formulations is its for-

mation of eutectic mixtures with palm oil, as shown in Figure 4, Chapter 6.

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Dairy products

PKO is the preferred replacement for butterfat in various dairy products because:

1. Countries like Malaysia, which have an inadequate supply of fresh milk, import

skimmed milk powder and make recombined ‘filled’ milk with locally available

vegetable oil. The product may be marketed in cans or as UHT processed in

tetrapak cartons.

2. There is less risk of deterioration during transport of skimmed milk powder than

of full cream milk powder.

3. Filled milk is cheaper.

4. In some products, better performance can be achieved with a ‘tailor-made’ fat blend.

There are long-standing recommendations from the International Dairy Federation for the

specifications of the oils to be used.These include clean flavour, low acidity and oxidation,

and low levels of trace metals and impurities. Refined PKO has no difficulty in meeting these

specifications.

Some ‘filled’ milk products are used as a powder – for example, coffee ‘whitener’ and cof-

fee ‘creamer’ used in drinks dispensers and provided in sachets in restaurants or fast-food

outlets.These products are required to have a long shelf life; therefore, fully hydrogenated

PKO (with zero trans fats) is preferred. PKO is a very suitable component for ice cream

and is widely used.

There is a limited market for cheese made with vegetable oil.A large part of cheese flavour

is derived from the short chain fatty acids in butterfat.A satisfactory mozzarella cheese can

be made using a blend of 70% palm kernel olein (PKOL) with 30% PO.This blend has a

similar solid fat content to butter but is cheaper.The fatty acids of PKOL help to develop

the desirable flavour. Mozzarella cheese is an important ingredient in pizzas. Danish-type

cheeses have been made using a blend of 50% palm oil, 40% coconut or PKO and 10%

rapeseed oil.

69

Frying

PKO and PKOL are suitable for frying. A particular use is for frying nuts intended for snack

foods or in bakery products. PKOL blended with palm olein is useful for shallow pan fry-

ing, but not deep fat frying, because the mixture tends to foam.The high stability of PKO

also makes it suitable for the ‘popping’ of popcorn.

Biscuits

A blend containing 40% PKOL with palm olein forms a eutectic mixture similar to that

described for PKO with palm oil. It finds applications as spray oil for certain types of biscuit

such as cream crackers. The purpose is to provide an attractive shiny appearance and to

act as a moisture barrier so that the crackers remain crisp.The high stability to oxidation

of the blend is important.

PKO is used in other types of biscuits such as Bourbon Creams, where two biscuits are sand-

wiched with a layer of PKO-sugar mixture. In the manufacturing process, the warm fluid fill-

ing is deposited mechanically on one biscuit and the second biscuit is placed on top. As

PKO crystallises very rapidly, the timing of the process must be judged so that there is still

enough liquid to ‘glue’ on the second biscuit.

Dietary product

A special use of PKO is in the manufacture of medium chain triglycerides (MCT).This

is a dietary product used for people with a metabolic problem, who are unable to

digest ordinary fats. MCTs are made by first fractionating the fatty acid components

of PKO and then re-synthesising those of the shorter chain lengths into triglycerides.

A blend of 80-90% of capric (10 carbons) and 10-20 % of caprylic (8 carbons) is pre-

ferred.

A major area of use for PKO – and one where considerable added value can be obtained

– is in fats for confectionery use.This is discussed in Chapter 8.

CHAPTER 8: CONFECTIONERY FATS

Palm oil and palm kernel oil (PKO) are, in different ways, valuable ingredients in confec-

tionery products. The best starting point to understand the special character required in

confectionery fats is cocoa butter, the fat of the cocoa bean.

When the Spaniards arrived in America in the 16th century they found the Aztecs were

making a popular drink called 'chocolatl' from powdered roasted cocoa beans. Recipes also

contained maize and flavouring like chilli or vanilla.

Research has shown that this drink was in use more than 3,500 years ago. Ancient pottery

vessels found in southern Mexico, where the cocoa tree is native, contained brown

residues. When analysed, the residues were found to contain theobromine, an important

substance specific to the cocoa bean.

The Spaniards introduced the bean and its use as a drink to Europe. It became a luxury

item favoured by the aristocracy. Chocolate bars, as we know them, were developed in the

18th century, with Fry of Bristol being a pioneer.

The chocolate bar requires extra fat over and above the natural fat content of the bean.

The added fat is obtained by pressing roasted cocoa beans, leaving a cocoa powder with a

much reduced fat content.

CHARACTERISTICS OF CHOCOLATE

Chocolate has a number of attributes valued by the consumer. It has an attractive, smooth

but shiny appearance.The chocolate bar has a firm solid texture and breaks cleanly when

a bite is taken. It melts rapidly in the mouth, releasing its complex flavour.

The flavour is developed in two stages.After harvest the beans are allowed to ferment nat-

urally for 2-3 days before being dried. Later they are roasted and ground, resulting in the

cocoa mass used in chocolate.

The appearance, texture and melting behaviour depend on the properties of the fat,

whereas the flavour is derived mainly from the cocoa solids.

70

The formulae for chocolate vary quite widely between manufacturers, but Table 1 shows a typ-

ical example of plain chocolate and the composition of the roasted ground bean (cocoa mass).

Cocoa butter is much more expensive than other vegetable fats - at the time of writing, it

is 21/2 times the price of palm oil.Therefore, there is interest in the use of alternative fats

which must not, however, alter the physical appearance and melting behaviour of the

chocolate.

There are two possibilities: firstly to replace some or all of the added cocoa butter in

chocolate; and secondly to make a more economical product using an alternative fat with

cocoa powder. Each approach has limitations.

The concept of chocolate is protected legally in many countries. In the European Union (EU)

the amount of vegetable fat that may be added is restricted to 5% of the end product.

The properties of PKO products are quite similar to those of cocoa butter, as is evident

from the solid fat content (SFC) curves shown in Figure 1.

Unfortunately the lauric oils are not compatible with cocoa butter.They form eutectics, sim-

ilar to that formed with palm oil.The chocolate is softened and loses its desirable crispness.

Cocoa butter

The composition of cocoa butter is very simple (Table 2).The fatty acids are also the major

components of palm oil, albeit in different proportions. However, early attempts to make

confectionery fat from palm oil were unsuccessful.

71

In 1956, researchers at Unilever obtained a patent for a cocoa butter equivalent (CBE) fat;

in other words, a fat that can be mixed with cocoa butter in any proportion without chang-

ing its hardness or melting behaviour.

This achievement required first a detailed knowledge of the triglycerides present in cocoa

butter. Typically three major components1 made up 85% of the fat: POP (18%); POSt

(39%); and StOSt (28%).

These glycerides are symmetrical, with the unsaturated oleic acid placed on the glycerol

molecule in the middle position between the two saturated fatty acids.This proved to be

an essential feature of a compatible fat.

72

1 P = palmitic acid, St = stearic acid, O = oleic acid

The fatty acids are of similar chain length and identical structure, resulting in the character-

istic sharp melting behaviour of cocoa butter. Palm oil contains two of these glycerides in

useful concentration, i.e. POP 29% and POSt 5%. They can be concentrated by a partial

crystallisation and filtration to separate the higher melting portion and a second crystallisa-

tion at a lower temperature to remove the more unsaturated portion.

The resulting palm mid-fraction (PMF) forms about 20% of the original palm oil and con-

tains typically 57% POP, 11% POSt and 2% StOSt. PMF is miscible with cocoa butter but

has a lower melting point and, to match its characteristics, it needs to be blended with

another fat rich in StOSt.

A number of seeds from tropical trees have a suitable fat; in some cases the desired com-

ponent has to be concentrated by fractionation.Their content of the important glycerides

is shown in Table 3, together with cocoa butter.

Seed fats

It is not possible to prepare blends which exactly match the main glycerides of cocoa but-

ter, but blends are available that are completely compatible with cocoa butter (Table 4).

In terms of availability, all the seed fats listed in Table 3 (except PMF) present some difficulty.

Illipe nuts are obtained from tall forest trees growing in remote parts of Borneo.The trees do

not flower every year and the harvest of nuts can vary from nil to 50,000 tonnes. Attempts

73

to grow them in plantations have not succeeded. Furthermore, they grow in rainforests and

the harvest is gathered from the ground, so a varying degree of biodegradation occurs.

Shea nuts are also gathered from the ground in the rainforests of West Africa.The oil con-

tent is 44-55%, but includes some undesirable components and the oil is difficult to refine.

Sal nuts are collected from forest trees in India. Supplies of kokum fat are small, but its high

content of StOSt is valuable. Most mangoes are consumed as fresh fruit, so kernel collec-

tion is only feasible from those that are industrially processed.

Cocoa butter from different sources shows some variability - the Brazilian product is soft-

est, while Malaysian cocoa butter is the hardest. At least some of this variability is due to

climatic conditions. This was proved by a very elegant experiment, in which heating was

provided to raise the temperature of half of a tree by a few degrees during the period of

fruit formation.The warmer part of the tree produced significantly harder fat.

Hardness at room temperature is a highly desirable characteristic, provided the melting at

mouth temperature is still rapid. It is possible to improve the behaviour of Brazilian cocoa

butter by using a CBE rich in the StOSt glyceride, such as kokum fat.The EU legal defini-

tion of chocolate permits the addition of vegetable fat from the list shown in Table 3 at a

level of 5% of the finished product, equivalent to about 15% of the fat content. Legislation

varies elsewhere.

Improving chocolate behaviour

Since the price of CBE fats is often half or less than that of cocoa butter, such additions

represent a worthwhile saving and can help improve the behaviour of the chocolate.

74

The formula of dark chocolate (Table 1) can be modified by using 7 parts of cocoa butter

and 5 parts of CBE as the added fat.

Products containing more than 5% CBE may no longer be called chocolate. They are

described as super coatings. All the added cocoa butter can be replaced by CBE or, to go

further, a low-fat cocoa powder (containing 11% cocoa butter) can be used in place of

cocoa mass together with a higher level of CBE.

A large part of today's market for chocolate is for milk chocolate, in which usually there is

less cocoa and a large part of the overall flavour is given by the milk solids and fat. Butterfat

contents of 5-20% or even higher are used in different quality products.The butterfat soft-

ens the texture of the chocolate. By selecting a CBE fat such as Blend 4 or 5 in Table 4, a

firmer product is obtained.

CRYSTALLISING OF CHOCOLATE

Molten chocolate is a suspension of the solid ingredients in liquefied fat.To obtain the shiny solid

surface, a special method of crystallising the fat is used.The chocolate is cooled slowly, with con-

stant stirring until it thickens. It is then carefully warmed a few degrees and allowed to set.

The science behind this process is fascinating.Although the glyceride composition of cocoa

butter is very simple, its crystallising behaviour is very complex. It can go into six different

arrangements of the glycerides in the crystals, with increasing melting points (Table 5).

The desired form giving a shiny surface is Form V. During the crystallising process, a mixture

of the forms develops. By reheating the mass to just below the melting point of Form V, the

less stable forms melt. Subsequently the remaining crystals act as nuclei to induce recrys-

tallisation in Form V.

Transition to Form VI, which is the most stable form, can be induced by temperature fluc-

tuations during storage. Formation of Form VI, which is characterised by larger crystals, leads

to some fat crystals appearing on the surface of the chocolate, giving it a grey appearance

called 'chocolate bloom'.While this is harmless, it is unattractive and consumers may think

it indicates mould. As the Form VI develops further the chocolate loses its smooth texture

and becomes gritty on the palate.

75

Figure 2 shows electron micrographs of all six forms. At the thousand-fold magnification

used, the difference between Forms V and VI is dramatic.The last section shows the crys-

tals of bloom on a bar of chocolate, clearly of Form VI.

76

CONFECTIONERY FATS FROM PKO

PKO has the rapid melting characteristics required in a confectionery fat, but its melting

point (28°C) is too low for a direct replacement of cocoa butter in chocolate.

Figure 1 shows the SFC curves of cocoa butter and various PKO products.The stearin pre-

pared from PKO has a solid content profile very close to cocoa butter. Hydrogenated

stearin (having virtually zero trans fats) is also suitable for chocolates, especially in hot cli-

mates.

Because PKO products cause an unacceptable softening of the chocolate, they can be used

only if the cocoa butter content is 5% or less of the product. This means using a low-fat

cocoa powder. A typical formula using palm kernel stearin (PKSt) as a cocoa butter replac-

er (CBR) is shown in Table 6.

The total fat content is 32.5%, of which 1.5% is cocoa butter contributed by the cocoa

powder. Figure 3 shows chocolate made with hydrogenated PKSt.

PKO products can develop off flavours if a fat splitting enzyme (lipase) - derived from con-

tamination by yeast or mould - is present.The lipase splits off some fatty acids and the short

chain acids characteristic of PKO have a strong soapy flavour.

Contamination can be introduced by an ingredient such as milk powder or as a result of

poor hygiene. Precautions need to be taken by testing ingredients and ensuring good

hygiene.This drawback does not arise when a non-lauric confectionery fat is used.

Other CBRs

Fats with a suitable sharp melting behaviour can be made by partial hydrogenation of oil

77

high in oleic acid. Palm olein is a good starting material, although other fats are also used.

It is necessary to use a catalyst and hydrogenation conditions that maximise the formation

of trans-oleic (elaidic) acid.

A typical product has about 18% trans fats and only a small increase in the saturated stearic acid.

However, it does not fit in well with current recommendations to minimise trans fats in foods.

Coatings for ice cream

Ice cream bars and lollies (stick confectionery) coated in chocolate are very popular.They

are handled at a low temperature (below -10°C) from manufacture to retail sale. A true

chocolate is very brittle under these conditions and often flakes off.

Suitable fat blends are specially formulated according to the method of use. For bars a palm

oil-PKO blend can be used, the lower melting eutectic being an advantage here.

For stick confections a PKO or coconut oil blend with liquid oil may be used.The manufac-

turing process involves dipping the ice cream into the coating, withdrawing it and, in some

cases, applying a layer of crushed nuts or crisp biscuit crumbs.The coating must be 'tacky'

to permit adhesion of the layer, and must set immediately before being packed. The oil

blend is subtly adjusted to the timing of the process.

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79

CHAPTER 9: FRYING OILS

Palm oil and palm olein are widely used for frying because they are economic and effec-

tive. However, it is of primary importance for every business to understand the competi-

tion it faces.This chapter describes the development of alternative oils in the context of the

technical requirements for satisfactory frying oil.

Most cooking processes are carried out at the boiling point of water (100°C).This is true

even in oven baking. Although the oven temperature is well above 100°C, the high mois-

ture content of food, such as meat joints and cake batter, means that the food itself does

not get above 100°C except for the surface layer, which develops a brown crust and an

attractive flavour.

Similarly during frying, which is carried out with the oil heated to a temperature of 170-

180°C, the food itself gets no hotter than about 100°C except on its surface. Frying in the

kitchen may be done in a shallow pan or in a deep pan. In the case of the shallow pan, a

little oil is used.The food is cooked on one side, turned over and cooked on the other side.

Virtually all the oil is absorbed by the food.

Some kinds of food, for example potato chips or French fries, are best cooked fully

immersed in a deep pan full of oil. A small proportion is absorbed and the rest is kept

for re-use. Deep pans are used in fast-food restaurants everywhere, while snack foods

such as potato crisps and instant noodles are manufactured in large continuous frying

baths.

Inevitably, over time, some chemical changes take place in the oil. Initially these con-

tribute to the desirable taste of the cooked food. However, over time, some oxidation

of the oil takes place, occurring mainly at the unsaturated double bonds of the fatty

acid chains. The resulting changes produce an unpleasant taste as the oil has become

rancid. Eventually some polymerisation occurs, the viscosity becomes higher and more

oil is absorbed into the food. When the quality of the food is affected, the used oil has

to be discarded and replaced. Clearly this has an important effect on the economics

of use.

Two main factors control the useful life of frying oil:

• The first is good practice in its use. The temperature must be controlled, the

equipment kept clean and the correct oil level maintained. During frying, oil is

absorbed by the food product and therefore removed from the pan. It is replaced

by fresh oil, so maintaining quality. Clearly a high rate of oil turnover is desirable.

• The second is the choice of frying oil. The susceptibility of an unsaturated fatty

acid to oxidation increases with the number of double bonds in the chain. Linoleic

acid (2 double bonds) oxidises 10 times more rapidly than oleic acid (1 double

bond), while linolenic acid (3 double bonds) oxidises at least 20 times more rapidly

than oleic.

Therefore oils with more than 3% linolenic acid are not regarded as suitable for

deep-fat frying.Vegetable oils all contain some minor components, the antioxidants,

which inhibit the action of oxygen on the unsaturated bonds.

The fatty acid composition of palm olein is shown in Table 1 on page 81. It has a very low

level of the sensitive linolenic acid and a moderate level of linoleic acid. The other main

components - palmitic and oleic acids - are highly stable to oxidation. In addition palm oil

and olein are relatively rich in protective antioxidants especially the Vitamin E tocotrienols.

These good properties have been recognised. It is estimated that globally some 10 million

tonnes of palm oil and palm olein are used annually in restaurants, fast-food outlets and

industrial deep-fat fryers.There is also substantial domestic use.

Nutritional guidelines

The high content of the saturated palmitic acid undoubtedly contributes to the stability of

palm oil in frying, but is often questioned with regard to its nutritional benefits, especially in

terms of blood cholesterol modulation.

With increasing understanding of the association between diet and health, many countries

have published nutritional guidelines for their populations.There is broad agreement among

developed countries that fat intake should be no more than 30% of total energy (current

fat consumption in the West is about 35-37% of energy).

80

Within that 30% it is recommended generally that saturated fatty acids (SFA) should be no

more than 10% of total energy intake, with polyunsaturated (PUFA) at 7-10% and mono-

unsaturated (MUFA) at 10% or more.

The recommended level of SFA refers to the total amount of fat consumed. Competitive

marketing considerations have led to a desire for the lowest possible SFA content in oils

used for frying. Some commodity oils fit this specification quite well, for example soybean

oil (SFA 15%) and rapeseed oil (SFA 7%).

However they also have high levels of PUFA, and especially of linolenic acid (>7%) and

therefore lack stability at the frying temperature. As a result, plant breeding programmes

for these oils and others have been undertaken to develop frying oil with a fatty acid com-

position that could confer higher stability.

81

Ideal specifications

It would be instructive to first draft a specification for frying oil that meets as far as possi-

ble the current nutritional and technical optima.

The following requirements need to be met:

• Linolenic acid less than 3%, as low as possible

• Linoleic acid - a good fried flavour needs about 10% while higher levels can lead to

off flavours due to oxidation

• Saturated acids below 15%

• Oleic acid 65-70%, can be higher

More precisely:

• Saturated acids 10-15%

• Oleic acid 65-75%

• Linoleic acid 15-20% (I would suggest 10-15% at most)

• Linolenic acid 1-2%

Palm oil and palm olein, in their current form, are excellent frying fats. However, given the

desire for higher oleic varieties and efforts to reduce saturates content, palm olein of

higher unsaturation - obtained through multiple fractionation - is becoming increasingly

available.

Through process innovations, it is possible to obtain palm olein with unsaturated fatty

acid content (mostly oleic) in excess of 62% of its composition. Advanced research,

especially through hybrid selection or genetic modification, has demonstrated the

potential to develop palm olein with a fatty acid composition that mirrors olive oil. Such

a composition would be competitive against the new varieties of frying oils described

next.

MODIFIED OILS

Several modified oils have been produced using conventional plant breeding techniques

and tested in frying trials. We will now review results of these breeding programmes and

of any practical frying results reported in using the modified oils.

82

Modern analytical techniques enable a single seed to be sampled and its fatty acid composi-

tion to be determined while the seed remains viable. If therefore, the analysis reveals an inter-

esting variation from the standard composition, the seed can be used for further breeding.

Furthermore, when the crop is an annual one, it is possible by the use of greenhouses and

artificial lighting to produce three generations per year. Rapid progress can be made

towards a new product. In contrast, the oil palm requires 3-5 years before the oil from a

new plant becomes available for testing and, furthermore, the replanting of a large area

would require some years compared to an annual crop.

Sunflower oil

A thorough collaborative project was carried out from 1994-1996 between different

research centres in the European Union to test the frying properties of High Oleic

Sunflower Oil (HOSFO). Palm olein was used in the trials as the reference oil.The compo-

sition of the oils used is shown in the first three columns of Table 1.The last column shows

the composition of Nusun, an equivalent product in the USA.

The oils were used to prepare, on an industrial scale, potato crisps and pre-fried frozen

French fries.The products were submitted to extensive analytical tests and to tasting tests

before and after storage.

The conclusion was that the HOSO was as good as palm olein for both the French fries

and potato crisps.The storage life of the potato crisps was shorter than when palm olein

was used, but adequate for retail purposes.

83

Today HOSO is increasingly used for snack food frying in Europe, either replacing palm olein

or used in a blend with it. Consumption figures for the high oleic oils are not available in Europe

but in the USA, 200,000 tonnes/year of the equivalent Nusun is currently in use. However, a

significant premium accompanies HOSO, curtailing its use for many low-cost foods.

Rapeseed oil

A high oleic rapeseed oil has been developed by the Dow chemical company, under the

name Natreon. Its composition in comparison with typical commercial oil is shown in Table 2.

The most important feature of the Natreon composition is the reduction in the highly-sen-

sitive linolenic acid.The oil was compared in domestic scale deep-fat frying of potatoes with

HOSO and palm olein.

The conclusion, after a number of analytical tests and tasting of both the used oils and the

French fries, was that the three oils were comparable. The potatoes still had acceptable

taste after the oil had been used for 66 hours. No production figures are available for high

oleic rapeseed oil, but it is in commercial use.

Soybean oil

Experimental quantities of soybean oil with various modified compositions have been pro-

duced (Table 3). Small-scale frying trials were conducted with bread cubes, potato crisps,

French fries or tortilla chips.The modified oils all performed better than the standard oil.

Significantly better flavour and storage performance were reported for the oils with the

lowest linolenic acid content. In one trial, oil with 0.8% performed better than one with

2.0%.This result provides good evidence for the recommendation for a minimal content of

linolenic acid. The oil with raised oleic and low linolenic acid gave very good results. The

only production figure reported for Asoyia was about 10,000 tonnes in 2009.

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Peanut oil

Peanut oil has long had the reputation of being excellent as frying oil for snack foods.

However, some cultivars of peanuts are being grown commercially in the USA in which

oleic acid content is increased and the linoleic acid decreased.

Standard oil typically has 53% oleic acid and 27% linoleic acid and, in addition, the saturated

long chain acids arachidic (0.5%), behenic (2.5%) and lignoceric (1.0%), with 20, 22 and 24 car-

bon chains respectively. High oleic cultivars have 76-81% oleic acid and only 3-5% linoleic acid.

The modified oil is more stable to oxidation but the linoleic acid content is too low for opti-

mum 'fried' flavour development. Behenic and arachidic acids are unique fatty acids occurring

in peanut oil.Their nutritional implications at high levels of consumption are still unclear.

Cottonseed oil

Standard cottonseed oil contains 28% saturated acids (mostly palmitic), 17.5% oleic acid

and 52-56% linoleic acid. One strain has been produced in Australia with 77% oleic acid,

the increase being mainly at the expense of the linoleic acid content.The oil is more suit-

able for frying.

Other oils

Modified oils have been produced from three other commercial oilseed crops but are not

yet commercialised as far as can be ascertained.Their compositions are given in Table 4.

The modified corn oil and safflower oil fit the ideal specifications for frying oil. Neither of

the modified linseed oils is good for frying, one with still too much linolenic acid and the

other with high linoleic acid content.

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It may be concluded, therefore, that palm oil and palm olein will meet growing competition

from other oils, despite higher cost.The latter have the advantage that they can be grown

in a wide range of temperate climates.

One practical way of improving the properties of palm olein has been demonstrated in a

project carried out at the Malaysian Palm Oil Board. A good quality palm olein was inter-

esterified with methyl oleate.The product was fractionated to give a new olein with Iodine

Value of 81 and a cloud point of -1.5C.The oil had oleic acid (60.5), linoleic acid (16.0%)

and saturated acids (22.6%), quite comparable with the liquid oils.

Blended oils

Blended oils provide the best cost-benefit opportunity to produce frying oil with optimised

fatty acid composition. Such blends can be made with two or more commodity oils.

Work has been reported from Iran on two-component blends of palm olein with rape-

seed (canola) oil, olive oil and corn oil, and on three-component blends of canola/palm

olein/olive and canola/palm olein/corn oil. In each case canola was 75% of the blend.The

frying performance of the blends was superior to that of canola, especially the 3-compo-

nent blends. In India coconut oil was blended with sesame or palm olein. The latter had

the better frying performance.

In most cases, it has been demonstrated that palm oil and/or palm olein could be one of

the major components, blended with any of the commodity seed oils that are otherwise

limited in their usefulness for use as frying fats. The palm oil component significantly

improves the keeping properties of the blends and the proportions can be adjusted to give

the desired clarity during storage.

86

87

CHAPTER 10: LOW TRANS FATS FORMULAE

It is useful to bring together the low trans fats formulae proposed earlier, with new pub-

lished studies relating to a wide range of food products.

The product formulae that will be discussed have met the laboratory test for function-

ality and in some instances have been adopted for manufacture. However, they may

well require minor modification for specific market requirements. In any case, they

should properly be submitted to a test market, as would normally be done for any new

product.

The physical characteristics of palm oil products are shown in Figure 2, Chapter 6 with

those of butterfat for comparison. It is apparent that palm oil products are suitable as major

components of food fats.

Palm stearin is an ideal high melting component (of zero trans fats content) to provide con-

sistency in place of hydrogenated oils. The process of interesterification is often the best

way to incorporate palm stearin in a blend with other oils. By the use of high temperature

and a catalyst, the fatty acids become detached from the glycerol backbone of the fat mol-

ecule and re-attached in a random manner.

For example, if palm stearin is reacted together with a suitable proportion of soybean oil,

a semi-solid fat results with a consistency similar to butter.The change in physical behaviour

is illustrated in Figures 1 and 2 on page 87, which relate to a practical application using palm

stearin and palm kernel olein.

BAKERY SHORTENINGS

1. The Malaysian Palm Oil Board (MPOB) has processed on a pilot scale a number of zero

trans fats shortenings. In each case, the performance was assessed by comparison in a

standard cake-baking test with a high quality commercial shortening. Some trans-free

shortening formulae are given in Table 3, Chapter 4.

2. Workers in Denmark have published formulae for a conventional and a liquid shortening

for cakes (Table 1).

3. Belgian workers have proposed an interesterified blend of 30 parts soybean oil with 70

parts of palm stearin (melting point 55.5°C, Iodine Value 34.8) as a basis for margarine

and also shortenings.

4. American workers have been accustomed to formulating mainly with various grades of

hydrogenated soybean oil, which result in high trans fats content. Several methods for

reduced or zero trans fats products have now been proposed:

• The use of a hard stock of 50% fully hydrogenated (therefore zero trans) soybean

oil interesterified with 50% soybean oil: When this hard stock was blended with an

equal quantity of soybean oil, the resulting shortening had a solid content profile

close to commercial products. However, no practical baking tests have been

reported.

• Blends with suitable proper ties for a bakery shor tening were obtained by

interesterifying 15 parts fully hydrogenated soybean oil with rapeseed oil and palm

stearin (melting point 53.7°C) in various proportions.

• 71% rapeseed oil and 29% stearic acid were interesterified: 52 parts of this were

blended with 33 parts palm mid-fraction and 15 parts cottonseed oil.This blend

was made into margarine which was comparable with two products in the market.

88

• Partly hydrogenated oils were prepared by a special process which gave lower

trans fats content. Canola, soybean, safflower and sunflower oils were used. Some

hydrogenation was done with a conventional nickel catalyst, followed by a second

step using a special platinum catalyst.When blended with soybean oil to get a solid

fat content (SFC) suitable for spreads and also shortenings, the product had trans

fats content of 2% or less.

• 25% fully hydrogenated soybean oil interesterified with 75% palm oil, alternatively

80% soybean oil interesterified with 20% fully hydrogenated soybean oil: The

products are diluted with 20 parts soybean oil for tub margarine.

5. Canadian workers interesterified 40% palm stearin with 60% palm kernel olein.These are

both the less valued products of the respective fractionations. Figure 1 shows the SFC

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profile before - and Figure 2 after - interesterification.The undesirable long 'tail' of the

blend, which would give poor eating properties, has been eliminated.

6. An approach similar to the Canadian example has been to interesterify palm stearin with

palm kernel oil.

MARGARINE AND SPREADS

Some trans-free margarine formulae are given in Table 2, Chapter 6.

In recent years the market for spreadable fats has moved strongly towards reduced-fat

spreads. The MPOB has published some suitable formulae. For soft blends suitable for

plastic tubs the range of 25-50% palm oil with 75-50% sunflower oil is suitable. For pack-

ets, formulae within the range of 80-75% palm oil, 10-15% sunflower oil and10-0% palm

kernel oil are recommended. Similar blends using interesterification also have the right

properties.

In Chapter 1, we indicated that the practical approach to obtaining low and zero trans

products is by incorporating either palm stearin or fully hydrogenated liquid oil, often cou-

pled with interesterification.This approach is now being adopted very widely.

VANASPATI Vanaspati was developed in India in 1930 as a substitute for butterfat ghee. It was made

from partially hydrogenated groundnut oil and cooled so that it crystallised in large gran-

ules with little free oil, to simulate the character of butterfat ghee.

Analyses from India, Pakistan and Iran in the 1980s indicated a high trans fats content of

30-50%. A high level of palm oil in vanaspati can substantively reduce or even eliminate

trans fats.

In India, little palm oil is used in vanaspati. A recent analytical survey revealed levels of

23.3% and 23.7% trans fats in two popular brands.These results received adverse com-

ment in the Indian press.The country's labelling regulations only require a declaration of

the range of trans fats content. In one case, 8-33% is declared which is not very helpful

to the consumer.

90

Indian workers have proposed two trans-free blends incorporating palm-based products

(Table 2).

The granular crystals desired are readily obtained in interesterified blends, as shown in Table 3.

Low and zero trans fats vanaspati formulae currently in use in Pakistan are detailed in

Chapter 6.

INDUSTRIAL FRYING

Industrial frying in restaurants and snack food factories requires oil with good resistance to

high temperature. Partly hydrogenated oils have been widely used in preference to liquid

oils, and inevitably there is a significant content of trans fats. As an alternative, palm oil pro-

vides the required high temperature stability naturally. Annually, at least 10 million tonnes

are used worldwide.

A particular application is in doughnut frying.The cooked product is given a sugar coating.

If liquid oil is used the coating falls off; therefore, hydrogenated oil is often specified by the

manufacturers of large-scale equipment. Experience has shown that palm oil has the nec-

essary properties to ensure satisfactory adhesion of sugar.

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MINOR USES OF PALM OIL

Peanut butter

To prevent oil separation during storage of peanut butter, manufacturers add about 2% of

partly hydrogenated vegetable oil.This is now often replaced by a similar quantity of a hard

grade of palm stearin (zero trans fats).

Dried soups

The fat traditionally used in dried soup powders was beef fat.This was changed to partly

hydrogenated vegetable oil to avoid the cholesterol content and achieve good storage life.

Palm oil is now the preferred (zero trans fats) ingredient; where long-term storage is

required, partly hydrogenated palm oil is used (melting point 40-42°C), providing a low

trans fats option.

Pastry mix

The product consists of a flour-and-fat mix packed as a free flowing powder for home

use. Hydrogenated vegetable oil has been replaced by palm oil or palm oil blended with

10-15% palm stearin. By chilling the fat and the flour and using an appropriate mixing

machine, a free flowing powder is obtained. The user only has to mix in water and roll

out the dough.

While commercial concerns do not usually reveal their formulae beyond the legal labelling

requirements, it is clear from the many reports of development work that reformulation

with palm-based products is a favoured practice towards low trans fats content. This is

borne out by the high levels of palm-based imports by Europe and increasing intake by the

USA. Adverse publicity in the USA from 1986 onwards had reduced palm oil use in foods

to near zero at one time.

For those who do not have the resources to formulate trans-free products from scratch,

a number of suppliers in the USA, Europe and Malaysia offer blends of suitable hard stock

or finished product.These are mainly but not exclusively based on palm-based products.

One refiner in the USA specialises in supplying palm-based products to the domestic

industry.

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93

CHAPTER 11: PALM-BASED OLEOCHEMICALS

The production of chemicals from palm oil and palm kernel oil (PKO) is attractive because

the great variety of end products has much higher added value than the commodity oils

themselves.

At the time that Malaysia first ventured into the oleochemical industry in the late 1970s the

industry was mainly located in the USA,Western Europe and Japan. Comments were made to

the effect: 'Why do you want to do that? We already have plenty of capacity'. Nonetheless the

Malaysian industry grew with encouragement from the government and has taken a significant

share of the world market. Malaysia's exports to key destinations are shown in Table 1.

In many products there is direct competition from petrochemicals, but the oleochemicals

have advantages.They are from renewable resources and are much more easily biodegrad-

able and therefore environmentally friendly.These assets have become much more impor-

tant in recent years.

It is estimated that 14% of all oils and fats are available for non-food use.The oleochemi-

cals market has been growing at 2-3% a year. Malaysia, for example, exported 2.17 million

tonnes of oleochemical products in 2009 (Table 2).

This chapter1 describes the most important chemical steps to higher value products, and

lists some of the many applications of palm-based oleochemicals.

1The author acknowledges the collaboration of Prof RJ Hamilton in the preparation of this chapter.

THE BEGINNING

The 'splitting' of oils has been described as the 'gateway' to oleochemicals. Splitting was

first achieved with the use of alkali, resulting in the formation of soap and glycerol. Soap was

most likely the first oleochemical made by man, using wood ash from a bonfire as the

source of alkali.This primitive process is still carried on in remote Nigerian villages (Figures

1 to 3).

94

Soap is a worldwide commodity for personal and laundry use. Good quality toilet soap is

formulated with 75-80% of palm stearin or tallow and 20-25% of PKO or coconut oil.The

95

long chain fatty acids give foam stability, while the shorter chain acids of the lauric oils

impart good lathering and detergency. The world market for soap is over 10 million tonnes

a year, with Malaysia having supplied 381,448 tonnes in 2009.

In the industry today, fats are split very efficiently using a catalyst with water under high

pressure (50-60 kg/cm2) and temperatures around 260°C (Figure 4).The glycerol is sepa-

rated and concentrated, forming a valuable by-product.

The fatty acids may then be distilled to various levels of purity and marketed as such.

Alternatively they are further processed, as outlined in Scheme 1.

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Fatty acids

The saturated fatty acids can be made into different metal soaps. Calcium stearate is used

in cattle feed. Zinc, cadmium and lead stearates are used in the rubber, paper and plastics

industries.

Fatty alcohols

A fatty acid can be directly hydrogenated to give a fatty alcohol. Effectively the acidic group

-COOH at the end of the fatty acid chain is changed into the -CH2OH group of the alco-

hol. The reaction requires a catalyst (for example, copper-chromium oxide), hydrogen at

pressure (200kg/cm2) and a temperature of 300°C. Alternatively the methyl esters may be

hydrogenated.

The fatty alcohols are the first step towards an important group of synthetic detergents,

used in shampoos and washing-up liquids, among others.

Long chain alcohols have also been used to form an impervious layer to reduce evapora-

tion from water reservoirs in hot climates.

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NITROGEN COMPOUNDS

The starting point for a range of nitrogen compounds is the formation of a fatty acid nitrile

by heating the acid with ammonia to 300°C with a catalyst such as zinc oxide or alumina.

The further reactions are shown in Scheme 2.

(It should be noted that the nitrogen atom has 3 bonds available for combination, where-

as the carbon atom has 4.)

(1) is hydrogenated stepwise to give first the intermediate

R-CH=NH (2), the aldimine, and again to give R-CH2-NH2 (3) This is a primary amine.

Alternatively the intermediate (2) can be reacted with the primary amine (3) to give the

secondary amine (4).

If intermediate (2) is reacted with (4) we make a tertiary amine (5). All three bonds of the

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The nitrile

nitrogen atom have now reacted with alkyl groups. Further reaction, this time using an alkyl

chloride or an alkyl bromide, gives quaternary ammonium salts (6) and (7).

Product (7) is used as a disinfectant in the food industry, in breweries and in hospitals.

In formulae (6) and (7), R represents a hydrocarbon chain which can be of different lengths.

In product (7), for example, the reagent used in the final reaction has 14 carbon atoms and

is obtained from PKO. Another quaternary, distearyl dimethyl ammonium chloride, is used

in hair conditioners and fabric softeners.

A quaternary is used for concentrating minerals by ore flotation.The finely milled ore

is dispersed in a solution of the quaternary and air is vigorously blown through.

99

The ore particles are suspended in the stable foam that forms, and so separated from the

unwanted waste.

Other amines are used as corrosion inhibitors, as anti-static agents in textile manufacture,

as release agents in rubber mouldings and as additives in lubricants.

Fatty amides are water-proofing agents.

Betaines are derivatives of amino acids that occur widely in nature. Synthetic betaines are

used in shampoos, bubble baths and in heavy-duty cleaning agents.

Amine oxides are components of cosmetics and detergents.

Ethylene oxide chains can be built up to various lengths.The products form water-in-oil or

oil-in-water emulsions depending on the length of the chain (Scheme 3).

Biologically active fatty acid derivatives

• Methyl epoxystearate, made by oxidising methyl oleate, can be transformed in a

series of reactions to give aziridine, which acts as an anti-tumour agent.

• Fatty nitriles - see (1) in Scheme 2 - can be transformed into tetrazoles with anti-

viral activity.

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Primary amines can be 'ethoxylated' by reaction with ethylene oxide

Palm fatty acids for candles

Candles with good performance are obtained when double-pressed stearic acid is blend-

ed with paraffin wax in the ratio of 70:30.

Sulphonated methyl esters as a detergent

The methyl esters of palm stearin are fully hydrogenated and then sulphonated

with sulphur trioxide (SO3) to give sulphonated methyl esters (SME). Their effi-

ciency as detergents is as good as that of the petroleum derived linear alkyl ben-

zene sulphonates (LAS). However the SME are much more biodegradable than

LAS.

101

Furthermore SME are compatible with the proteolytic enzymes often added to washing

powders to remove milk, egg and gravy stains, whereas LAS are not compatible. SME based

on palm fatty acids are now in manufacture.

Polyurethane foam

Polyurethane is obtained by reacting a 'polyol', (an alcohol with many -OH groups) with an

isocyanate.The latter is obtained by introducing the functional group N=C=O into toluene.

Research at the Malaysian Palm Oil Board developed a process for making a polyol based

on palm oil and using it in polyurethane foam.The process has been patented.

Polyurethane foam can be made with flexible, semi-rigid or rigid characteristics and finds

many uses in furniture, insulation of roofs and pipework, and in construction. The world

market is estimated to exceed 10 million tonnes per annum, with the Asia-Pacific region

absorbing one-fifth of this.

Bio-diesel

The transformation of a triglyceride into the methyl esters used as bio-diesel is achieved at

moderate temperature with dry methyl alcohol and an alkali catalyst.

In the case of palm oil, the purification of the esters also yields valuable by-products, main-

ly Vitamin E and carotenes.The Palm Oil Research Institute of Malaysia started a project on

bio-diesel in the 1980s, built a pilot plant (Figure 7) and carried out extensive tests on road

vehicles to prove the effectiveness of palm oil for this application.

Bio-diesel has been promoted in the European Union with the objective of reducing green-

house gas emissions and to provide a new market for farmers who grow rapeseed.

European directives require industry to move towards the incorporation of increasing lev-

els of bio-diesel into the fuel offered to motorists at the pump. At the time of writing, the

level in the UK is 3.25%. In the USA, bio-diesel production from soybean oil has become

significant.

World production of bio-diesel was projected at 3,926 million gallons in 2009 and is esti-

mated to increase rapidly.The price structure of vegetable oils has made the import of palm

bio-diesel attractive and also the import of palm oil for transformation in Europe.

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USES OF OTHER FATTY ACID ESTERS

Esters of medium chain fatty acids with medium chain alcohols have various uses. Myristyl

myristate is a component of cosmetics, while isopropyl myristate is used in hair condition-

ers, lipstick and eye make-up. Glyceryl monolaurate is used in oil-in-water emulsions.These

esters are sourced from PKO.

A particularly interesting use of fatty acids from PKO is in the synthesis of medium chain

triglycerides (MCT).The following mixture is used:

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The MCT have special nutritional proper ties. They are broken down in the diges-

tive system more rapidly than fats of longer chain length. They are then transpor t-

ed as the free acids in the por tal blood stream and rapidly digested. They are

impor tant food sources for patients who have difficulty in digesting normal fats.

Owing to their rapid metabolism MCT have been proposed as energy sources in

the diet of athletes.

Glycerol

A consequence of the production of bio-diesel is a greatly increased supply of glyc-

erol, which has the following uses:

• As a component of alkyd resins used in paints

• In glyceryl monomethacrylate, which is polymerised and used in solar panels, etc

• In other polymers used by dentists

• In formulations of cleaners and polishes, of leather and textile processing aids

• As a humectant to keep tobacco moist and also as a minor ingredient of cakes and

in 'scoopable' ice cream

• In the explosive nitro glycerine

Potential new uses are the subject of research in a number of laboratories. A project at

a US Department of Agriculture laboratory uses glycerol as feed stock for selected

micro-organisms, one of which produces 'sophorolipids' of potential use in cosmetics

and detergents. Other organisms produce a polymer, poly hydroxyl alkanoate (PHA).

Depending on the bacterial strain used PHA, which is biodegradable, has uses in golf

tees, razor handles and bottles.

Cosmetic applications

Products from palm oil and PKO are used in some cosmetic items (Examples 1

and 2).

104

Example 1

Example 2

The ingredient list for a skin cream includes:

• Isopropyl palmitate

• Triple pressed stearic acid

• Glyceryl monostearate

• Medium chain triglycerides

• Glycerol

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CHAPTER 12: OILS AND FATS PROPERTIES

The physical properties of oils and fats are basic in relation to their practical use.This chap-

ter gives definitions of some physical properties and discusses their practical importance.

Density

The density of the oil is of great commercial importance because it is required for the

determination of the weight of oil in shore- and ship's-tanks.

Because it is impractical to physically weigh a shipment of several hundred tonnes of oil, the

volume of oil is measured in tanks that have been calibrated.The weight is then calculated

by multiplying by the apparent density.

The formal definition is the weight of a volume of the oil at a defined temperature divided

by the weight of the same volume of water at 4˚C.This is the Relative Density.The chosen

temperature is 4˚C because water has its maximum density at that temperature.

For practical use in determining the weight of oil in a ship's tank or a storage tank, the

Apparent Density is used.The term 'litre weight in air' is self-explanatory.The measurement

of the density is carried out in the laboratory and corrected to the actual temperature of

oil in the tank.To obtain the weight in the tank, we need to know the volume.The empty

head space in the tank (the ullage) is measured and the volume of oil obtained from a cal-

ibration chart previously prepared for the tank.

The change in density for most oils is 0.00068 per degree centigrade (it is 0.00071 for the

lauric oils) and therefore an error of 1°C represents 340kg of oil, quite a significant amount.

Accurate temperature measurement is made by the surveyor when sampling the tank. He

must make sure the tank contents are fully liquid, with no solid fats at the bottom.

The sampling device is first warmed by filling and emptying it.Then samples are drawn at

three levels and their temperature taken with an accurate mercury-in-glass thermome-

ter. The sampler should not be exposed to extreme ambient temperatures during this

measurement.

106

Figure 1 shows a temperature measurement being made on top of a shore tank. Note the

undesirable use of a copper or brass implement. Copper is a powerful catalyst for oxida-

tion of oils.

Colour

The colour of oils enters into trading specifications.The standards and the trade specifica-

tions for the colour of oils use the Lovibond scale. Mr Lovibond was a brewer in the English

country town of Salisbury in the 18th century. He devised a system of pieces of glass

coloured in red, yellow or blue of increasing intensity to standardise the colour of his pro-

duction.When measuring red, yellow or orange colours, only the red and yellow glasses are

needed.

The oil in a glass cell of a standard size is placed in an enclosed box fitted with illumination.

The oil colour is matched by using a suitable combination of the graded glasses. Oil colour

is generally given in terms of 'Lovibond red and yellow'. A 51/4-inch cell is used for refined

oil, and a 1-inch cell for the stronger coloured crude oils. Most refined vegetable oils have

a near-white colour. Refined palm oil is usually specified at a maximum Lovibond Red of 3.0

in a 51/4-inch cell.

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The strong colour of crude palm oil (CPO) is due to its content of various carotenoids

(pro-Vitamin A). These are partly removed with the use of bleaching earth and partly

destroyed at high temperature during refining. Experience shows that poor quality CPO is

difficult - or in extreme cases, impossible - to bleach to the specified colour of 3.0.The dif-

ficulty is not due to carotene residues, but to colour formed due to deterioration of the

oil.

Some laboratories use an empirical bleaching test to decide what treatment is needed

in the factory. A science-based measure to define bleachability of palm oil was developed

by the Malaysian Palm Oil Board (MPOB) and is now part of the buying specification for

CPO.

It consists of measurements of colour in a spectrophotometer at two wavelengths in the

ultraviolet part of the spectrum. One of these measures the carotene level. Carotene is

gradually destroyed by oxidation.The second measures the increase in oxidation products

of the fatty acids.The ratio of the two is a sensitive measure of the quality of CPO and is

simple and rapid. It is called the Deterioration of Bleachability Index or DOBI.

Another measurement of absorption, this time in the infra-red part of the spectrum, pro-

vides a measure of the trans fats content.

Slip melting point

The melting point of solid fats is a basic characteristic used in specifications. It is particular-

ly useful for describing hydrogenated fats and different grades of palm stearin and palm ker-

nel stearin.The conventional method for obtaining the melting point is described in Chapter

2.An instrumental method for determining the melting point was developed by the MPOB

(Figure 2).

Solid fat content (SFC)

The relationship of the SFC with temperature has been used in earlier chapters.The SFC

is much more informative about the character of a fat than the slip melting point. An

example of the marked difference between palm kernel oil - with a rapid change from

hard solid to liquid - and palm oil, where the change is much more gradual, is shown in

Figure 3.

108

The method of measurement most widely used depends on the response of a sample

to a magnetic field (the Nuclear Magnetic Resonance).The solid part of the fat responds

109

differently from the liquid part. By measuring the fat brought to a range of temperatures,

the familiar curves can be prepared.

Cloud Point and Cold Test

These two empirical measurements are used to characterise liquid oils.To determine the

cloud point, a tube of the oil is placed in a refrigerated bath and the oil temperature meas-

ured at which cloudiness is first observed.

The cold test involves placing a sample in an ice water bath. An oil that remains clear for

51/2 hours passes the test.The test indicates the ability of the oil to remain clear when kept

in a domestic refrigerator.

Both tests relate to the consumer's wish for a salad or cooking oil to be sparkling clear.

Standard palm olein fails to pass these tests. Double fractionation gives improved results,

but these are still inferior to the more unsaturated oils.

An acceptable cloud point can be obtained by blending palm olein with liquid oil as shown

in Figure 4. A proportion of about 30% of palm olein is suitable. Such blends are already

being marketed. Recently reported research shows that, after interesterification of palm

olein with methyl oleate, the new olein matches the characteristics of liquid oils.

110

Smoke Point

The smoke point is of interest in oils to be used for frying.The temperature is measured

while observing the steady evolution of smoke from oil being heated in an open vessel. A

high smoke point is a desirable characteristic. Smaller more volatile molecules, particularly

fatty acids, lower the smoke point and these increase during usage.

Figure 5 shows three curves for the smoke point obtained on oils containing increasing lev-

els of free fatty acids. Curve 1, taken from a text book, shows the effect of adding fatty acids

to refined oil. Curve 2 was obtained in the same way but using a lauric oil. Curve 3 was

obtained in the MPOB laboratories on used frying oils. It shows that, in addition to free fatty

acids, other breakdown products also affect the smoke point.

The lauric oils have a lower smoke point because of their content of the more volatile

medium and short chain acids.A high smoke point limit is often specified for frying oils since

it indicates a longer life in use.

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Flash Point and Combustion Point

As the oil continues to be heated, smoke evolution increases until the gases can catch light

and support combustion. Over-heated frying pans are a major cause of domestic fires, and

are also a problem in restaurants.

The flash point and combustion point are measured by heating the oil in a small closed ves-

sel with a sliding door at the top (Figure 6).The vessel is fitted with a thermometer pock-

et and a stirrer. During heating, the door is momentarily opened while a flame is applied to

the opening.The temperature at which the evolving gases momentarily light up is the flash

point. On further heating the gases will support the flame.This is the combustion point.

A modified apparatus is used for solvent-extracted oils to test that any solvent residues,

which have a very low flash point, are not at a dangerous level.

Polymorphism

The desirability of the small crystals of the beta prime (β') formed in shortenings and mar-

garines has been discussed in earlier chapters.

The term polymorphism is applied to the existence of a triglyceride in several crystal forms.

When a molten pure triglyceride is cooled quickly, the alpha (α) form is first obtained. If

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this is gently warmed it melts, but solidifies again to give the β' form. On further gentle heat-

ing, the β' form melts and re-solidifies in the beta (β) form.This is the final and stable form.

The reason for this behaviour is that the rather long fatty acid chains have difficulty in pack-

ing together in the tidy structure that is a crystal.The same behaviour applies to the mix-

ture of triglycerides that is a natural fat. Figure 8 shows the disposition of the α, β' and β

forms of tristearin.

Each triglyceride molecule looks like a chair, with two fatty acids facing one way and the

third in the opposite direction.The fatty acids are attached to the glycerol molecule, which

forms the seat of the chair, as it were.

In the α form, they are stacked vertically. In the β' form, they are stacked somewhat more

tightly at an angle to the vertical. The fatty acid chains are in zig-zag form, with adjacent

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chains at right angles. This is indicated in the diagram, where the middle chains zig-zag at

right angles to the plane of the paper. In the β form, the fatty acids are all aligned.

The different arrangement of the three forms is also evident when we look at the arrange-

ment of the glycerides end on, in cross-section (Figure 9).

In the α form, their position is rather random. In the β' form, the layers are aligned at alter-

nate angles, whereas in the most stable beta form, they all face in the same direction and

are closer together.

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Figure 10 shows how the layers of glycerides build up into a crystal. The example shows

the most stable form of trilaurin with the 12-carbon lauric acid chains.

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The distance between the glycerides within the layer and the distance between the layers

are measured by means of x-ray diffraction.A narrow beam of x-rays is deflected at angles

determined by the spacing between the glycerides.The measurements tell us that the glyc-

erides in the α form have the most freedom of movement, while those in the β form have

the least.

The melting points of the three polymorphic forms of some simple glycerides are given in

Table 1.

The crystallisation behaviour of cocoa butter is more complex than that of other fats. It

has six polymorphic forms, of which four are unstable and readily transform into the

more stable form V that is required.The main glycerides contain two saturated and one

oleic acid.

The final most stable arrangement arrived at is shown in Figure 11, where tristearin is

compared with 2-oleodistearin.The bend at the double bond of oleic acid is accommo-

dated in the crystal by aligning with an oleic acid from the adjacent 2-oleodistearin. So,

instead of the dimension of a layer being roughly the length of two fatty acids chains, it

is the length of 3.

The melting points of the six polymorphs of cocoa butter are shown in Table 5, Chapter 8.

Refractive Index

The speed of light is lower when it is passing through a medium, such as glass, water or

other liquid, than it is in vacuum. As a result a ray of light is bent at an angle in the medi-

um.The ratio of the speed of light in a vacuum to that in the medium is the refractive index

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(RI) of the medium. It is also the ratio of the sine of the angle of incidence to the sine of

the angle of refraction.The RI varies with the temperature.

The measurement is made in a refractometer where the sample is placed between glass

prisms, which are maintained at a constant temperature by water circulated through a

jacket.

The RI varies somewhat depending on the wavelength of light and this is conveniently con-

trolled in the laboratory by using a sodium lamp, which has a strong yellow line called the

D line in its spectrum.

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The RI also varies with the chain length of the fatty acids and their unsaturation and it

therefore has some value as an identity characteristic. It is listed in Codex Alimentarius and

other standard specifications, though for identification purposes it is somewhat outdated.

However, it is used for control of the hydrogenation process. The measurement is very

rapid and can be easily carried out close to the plant in the factory, or a continuously

recording refractometer can be fitted on the hydrogenation vessel.

A change of 0.00116 in the RI is equivalent to 10 units of Iodine Value, and the accuracy of

measurement enables a change of one unit of Iodine Value to be observed.This is sufficient

for most purposes.

It may be noted incidentally that, due to the need to minimise trans fats, hydrogenation is

much less practised than it was. Hydrogenation is now often used to saturate all double

bonds, so producing a zero trans fat which is then used by interesterification with oils to

produce consistent fats.

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