Introduction

-1-

CHAPTER 1

INTRODUCTION

1.1 Background The oyster mushroom, Pleurotus ostreatus is a common edible mushroom from the Kingdom

Fungi, Phylum Basidiomycota, Class Agaricomycetes, Order Agaricales and Family

richolomataceae. It was first cultivated in Germany during the year 1917 as a subsistence

measure during World War I and is now grown commercially around the world for food. Total

mushroom production worldwide has increased more than 18-fold in the last 32 years, from

about 350,000 metric tons in 1965 to about 6,160,800 metric tons in 1997. The bulk of this

increase has occurred during the last 15 years. A considerable shift has occurred in the composite

of genera that constitute the mushroom supply.

Oyster mushrooms are also known as Pleurotte. These oyster mushrooms get their name from

their oyster shell-like shape. They are white, light tan or ivory colored with a large, fan-like cap

and a smooth stem. Since these tender mushrooms have a delicate flavor, it is best to prepare

them simple so that the flavor is not overpowered. They usually grow on trees and fallen logs in

spring, summer, fall and during warm spells in winter. Oyster mushroom (P. ostreatus) contains

23.5 % Protein, 2.6 % Lipid, 39.4% Carbohydrate, 27.0 % Fiber and 7.4 % Ash. It is a rich

source of protein.

Dry matter of mushrooms is very low, usually in the range of 60–140 g/kg. Commonly, dry

matter content of 100 g/kg has been used for calculations if the factual value is unknown. Such

high water content and water activity affect the texture and participate in the short shelf life of

fruiting bodies. Mushrooms are rich in essential nutrients like vitamins, minerals, fiber,

antioxidants and water. They also boast the following properties: Mushrooms have little sodium

and fat and zero cholesterol. They are rich in vitamins of the B group: riboflavin, niacin, folate,

pantothenic acid, thiamin and B 6. The mushroom is the only vegetarian source of vitamin D in

edible form. Antioxidants in mushrooms include ergothioneine. Mushrooms are a powerhouse of

minerals, including potassium, copper, zinc, selenium, iron, magnesium, phosphorus and

calcium. A medium mushroom has more potassium than a glass of orange juice or a banana. A

serving of mushrooms supplies 40-60% of the daily copper requirement. Selenium is mainly

found in animal proteins, so the mushroom is the best source of selenium for vegetarians. The

source of the antibiotic penicillin, mushrooms have natural antibiotics with anti-fungal and anti-

microbial properties.

The combination of low fat and carbohydrates and zero cholesterol with high proteins, vitamins,

minerals, water and fiber makes mushrooms ideal for diabetics. Moreover, mushrooms contain

natural insulin and enzymes which break down the starch and sugar in food. Finally, certain

compounds stimulate the endocrine glands and the formation of insulin. Mushrooms are

beneficial for patients of hypertension, as they control the blood pressure. They are known to

Generated by Foxit PDF Creator © Foxit Softwarehttp://www.foxitsoftware.com For evaluation only.

-2-

control migraines and even some mental disorders. Niacin helps to prevent Alzheimer's and other

cognitive disorders. Natural antibiotics in mushrooms guard against infections and hasten healing

of wounds. Mushrooms are good for weight loss, while helping to build muscle mass.

Mushrooms not only have their own flavor which intensifies during cooking, but can absorb the

flavor of other ingredients. They can be used as appetizers, added to salads, soups, stews and

sandwiches. However, it is essential to identify mushrooms correctly, as the poisonous species

look similar to the edible kind. Moreover, some edible ones can be poisonous, depending on

where they are grown. One must buy mushrooms from trusted vendors. Mushrooms are rich in

vitamins, minerals, amino acids, fiber and antioxidants. They have curative and preventive

properties and contribute to all round good health.

Finger millet is important millet grown extensively in various areas of India and Africa. It is

nutritionally important because of its high calcium, iron and dietary fibre, compared to cereals

such as barley, rice, maize and wheat. Although fat content is low, ragi is high in polyunsaturated

fatty acids. Since finger millet is processed as a whole grain (i.e. without dehusking), it retains

the fiber, minerals, vitamins and phenolics present in the outer layer of grain, which are

nutritionally beneficial (Pednekar et al, 2009).

Barley (Hordeum vulgare vulgare L.) is an ancient and important cereal grain crop. It ranks fifth

among all crops in dry matter production in the world today (129 M mt, 2002–2005 mean)

behind maize (Zea mays, 605 M mt), wheat (Triticum spp., 549 M mt), rice (Oryza sativa, 424 M

mt), and soybean (Glycine max, 175 M mt), and ahead of sugar cane (Saccharum spp., 92 M mt),

potato (Solanum tuberosum, 60 M mt), and sorghum (Sorghum bicolour, 50 M mt), (FAO,

2007). Barley was presumably first used as human food but evolved primarily into a feed,

malting and brewing grain due in part to the rise in prominence of wheat and rice. In recent

times, about two-thirds of the barley crop has been used for feed, one-third for malting and about

2% for food directly. However, throughout its history, it has remained a major food source for

some cultures principally in Asia and northern Africa. Barley is arguably the most widely

adapted cereal grain species with production at higher latitudes and altitudes and farther into

deserts than any other cereal crop. It is in extreme climates that barley remains a principal food

source today, e.g., Himalayan nations, Ethiopia, and Morocco.

The mixed linkage (1→3)(1→4)-β-D-glucans (β-glucan) from the endosperm of cereal grains are

valuable industrial hydrocolloids and have been shown to be important, physiologically active

dietary fiber components. β-glucans are water-soluble, linear, high molecular-weight

polysaccharides. They give viscous, shear thinning solutions even at low concentrations. The

viscosity is related to the molecular weight and is strongly dependent on concentration (Lyly et

al, 2004). The good viscosity forming properties make β-glucans potential alternatives as

thickening agents in different food applications, e.g. ice creams, sauces and salad dressings.

Barley flour can be used as an ingredient for the preparation of soup powder.


-3-

Extrusion cooking is an important and popular food processing technique. Cereals are common

ingredients in extruded products and barley flour has been incorporated into some extruded

human. Extrusion cooking has been used for processing breakfast cereals, pasta products,

dextrinized flour, etc. Some of the advantages that have been attributed to this technique include

low cost, high productivity, versatility and unique product shapes. Depending on the intended

final product, various temperatures, moisture, shear and screw speed combinations can be used.

Extrusion cooking of starchy grain flours causes gelatinization of starch among other physico-

chemical and functionality changes the grain components undergo.

Mushroom soups available in the market contain not more than 2% dry mushroom. Since

mushroom is rich in protein (23.2±0.5%), an increased amount of mushroom powder also adds

high nutritional values to the soup. In an addition, Barley and Ragi flour can also enhances crude

fiber content in food materials.

In this study, Oyster mushrooms were used to prepare for extruded product rich in protein and

crude fiber. Barley and Ragi flour were also used in order enhance the nutritional attributes in the

final product. The product was rich in protein and also, due to gelatinization of starch, the

properties of Barley flour, Ragi flour and mushroom powder was changed.

1.2 Objectives:

Based on above considerations the present investigation was undertaken with the following

objectives:

1. To develop protein enriched ingredient for the preparation of mushroom soup powder using

twin screw extruder.

2. To optimize the process parameters for the preparation of the mushroom soup ingredient.


-4-

CHAPTER III

REVIEW OF LITERATURE

This chapter reviews the research work carried out by various researchers in related areas viz.

extrusion cooking, extruded characteristics like hardness and water solubility index, response

surface methodology in process variable optimization and sensory evaluation.

2.1 Principle of Extrusion Cooking

Extrusion cooking is a versatile process that combines several unit operations including mixing,

shearing, conveying, heating, puffing and partial drying, depending on the extruder design and

process conditions. Extrusion cooking plays an important role in the production of snack foods

as well as breakfast cereals, modified flours and sweets. Extrusion is a cooking and shaping

process designed to give unique physical and chemical functionality to food materials. High

pressures and temperatures are common in cooking extruders, thereby causing changes in the

physical and chemical properties of extruded starch. The effects of extrusion on water solubility

and water absorption of starch have been studied extensively (Anderson et al., 1969). Food

extrusion is a process in which food ingredients are forced to flow, under one or several

conditions of mixing, heating and shear, through a die that forms and puff dries the ingredients

(Rossen and Miller, 1973). Extrusion cooking has some unique features compared to other heat

processes, because the material is subjected to intense mechanical shear. It is able to break

covalent bonds in biopolymers, and the intense structural disruption and mixing facilitate

reactions otherwise limited by dilution of reactants and products. The nutritional value in

vegetable protein is usually enhanced by mild extrusion cooking conditions, due to an increase in

digestibility. This may be due to protein denaturation, and inactivation of protease inhibitors

present in the raw plant foods. Extrusion cooking, as a heat treatment affects and alters the nature

of many food constituents, including starches and proteins, by changing physical, chemical and

nutritional properties. It has become a mature process for many applications in the food industry.

In the food industry, high temperature–short time extrusion cooking is used to produce direct

expanded products such as snacks, breakfast cereals and pet foods.

2.2 Advantages of Extrusion Cooking

a) It is versatile.

b) It facilitates high productivity.

c) It gives high quality products.

d) There is a possibility of giving different product design and shape.

e) There is absence of effluents during processing

f) It improves the functional characteristics of protein source without losing the protein quality

provided if right sets of process variables used.


-5-

g) From the nutritional point of view protein from by-products like waste of traditional food

industry or new agronomics species of several grains that have not been consume because of

their acceptability. It can be reversed by extrusion through extruder.

2.3 Extruders

Extruder is primarily a screw pump, and is capable of performing mixing, heating, cooking and

shaping. In principle, it is a high-temperature short-time reactor based on mechanical and

thermal energy input, and usually combined with a structuring and shaping step at the die exit.

Feed ingredients during their movement inside the screw are transformed to continuous plastic

dough. The barrel is externally heated by either steam or electric heaters. Upon heating and

working during extrusion process, macromolecules in food ingredients lose their native,

organized tertiary structure and form continuous viscous dough. The laminar flow within the

channels on the extrusion screw and the die aligns the large molecules in the direction of the

flow, exposing bonding sites which leads to cross-linking and formed, expandable structure that

creates the crunchy texture in fabricated foods. Food extruders can be visualized as devices that

can transform variety of raw ingredients into intermediate and finished products. Food extruders

can perform one or several functions at the same time while processing food or feed: mixing,

homogenization, grinding, shearing, starch cooking, protein denaturation, texture alteration,

enzyme inactivation, pasteurization and sterilization, cooking, shaping products, expansion and

puffing, agglomerating ingredients dehydration and unitizing (Riaz, 2000).

2.4 Characteristics of Extruded Products

a) Degree of expansion on exit from the extruder.

b) Bulk density.

c) Mechanical Properties.

d) Internal Microstructure.

e) Protein quality.

f) Starch characteristics.

g) Degree of cook.

Altan et al. (2008) evaluated effect of extrusion parameters on the quality of tomato pomace-

Barley blend. The results showed that varying levels of tomato pomace could be incorporated

into an extruded barley snack depending on the desired texture of the final product. Extrudates

with 2% and 10% tomato pomace levels extruded at 1600C and 200 rpm had higher preference

levels for parameters of color, texture, taste and overall acceptability. Such extrusion would also

provide another avenue for tomato pomace utilization.


-6-

2.5 Mushrooms

Adejumo and Awosanya (2004) determined the proximate and mineral composition of four

edible mushroom species from South Western Nigeria. Results of proximate analysis of four

edible species of mushroom indicate that Termitomyces mammiformis was a very good source

of crude protein (37%), crude fiber (7%), ash (10%), calcium (216 g/kg dry weight) and

manganese (136 mg/kg dry weight (dw)). Russula vesca was the richest in carbohydrate (71%)

and magnesium (14 g/kg), while Lactarius triviralis was richest in moisture content (37%), iron

(1230 mg/kg) and copper (8 mg/kg). It is also a good source of carbohydrate (64%), calcium

(210 g/kg) and manganese (120 mg/kg). Lentinus tigrinus was, however, the richest in dry matter

(94%), and is also rich in carbohydrate (62%), magnesium (11 g/kg) and copper (6 mg/kg). It

was observed that lipids, sodium and phosphorus contents of the four species were generally

very low.

Tons of wild growing mushroom species have been widely consumed as a delicacy by part of the

European population. The credible evaluation of their nutritional value has so far been limited,

due to the fragmentary knowledge of their composition and mainly due to the poor information

on the bioavailability of their constituents. Dry matter content is very low, commonly about 100

g/kg. A low proportion of lipid and glycogen results in a low energy value. Relatively high

proportion of insoluble fiber, comprised of chitin and other structural polysaccharides, seems to

be nutritionally profitable. The proportion of essential amino acids is contributive, while that of

�n 3 fatty acids is nutritionally negligible. The contents of potassium and phosphorus are higher

than in most vegetables. Relatively high ergosterol content could be of significance for

individuals with a low intake of ergocalciferol. Some mushroom species have relatively high

antioxidant capacity. Specific b-glucans have been studied for pharmacological use (Kalac,

2009).

2.5 Drying of Mushroom

Chen and Chen (1974) studied the effects of dehydration on the volume contraction of

Muahrooms. The experimental results showed that the the volume shrinkage of the sliced

mushrooms was a linear function of moisture content in the range from an initial moisture

content of 15.66 g/g of dry solid (or 94% moisture content) down to about 0.1 g/g (or about 9%

moisture content). The shrinkage curve was made based on the experimental data and it was

compared with the computed data. The model fitted reasonably well. The empirical equation was

substantiated by a recent theoretical derivation.

Brennan et al. (2000) studied the effect of post-harvest treatment with citric acid or hydrogen

peroxide on the Shelf Life of Fresh Sliced mushrooms. In this study, whole fresh mushrooms

were soaked for 10 min in solutions of citric acid or hydrogen peroxide, then sliced, packed and


-7-

stored at 40C for up to 19d. Both treatments reduced the number of pseudomonad bacteria and

improved the keeping quality of the sliced mushrooms when compared to control (water soaked)

slices. A specification of 75 Hunter L units was established to quantify sliced mushroom shelf

life and this showed that the treatments extended the shelf life by about 50%. Treatment

effectiveness varied with mushroom batch, with first and third flush mushrooms from phase III

compost responding better than mushrooms from phase II compost and second flush. The citric

acid treatment had no deleterious effect on the sensory properties of sliced mushrooms

Bergstrom (2006) studied wheather enzymatic pretreatment of Shiitcake Mushroom enhance the

extraction process of valuable substance eritadenine. The results obtained with enzymatic pre-

treatment showed deterioration compared to extraction without enzyme treatment.

Giri and Prasad (2007) evaluated Microwave-vacuum dehydration characteristics of button

mushroom (Agaricus bisporus) in a commercially available microwave oven (0–600 W)

modified to a drying system by incorporating a vacuum chamber in the cavity. The effect of

drying parameters, namely microwave power, system pressure and product thickness on the

drying kinetics and rehydration characteristics were investigated. The drying system was

operated in the microwave power range of 115–285 W, pressure range of 6.5–23.5 kPa having

mushroom slices of 6–14 mm thickness. Convective air drying at different air temperatures (50,

60 and 700C) was performed to compare the drying rate and rehydration properties of

microwave-vacuum drying with conventional method. Microwave-vacuum drying resulted in

70–90% decrease in the drying time and the dried products had better rehydration characteristics

as compared to convective air drying. The rate constants of the exponential and Page’s model for

thin layer drying were established by regression analysis of the experimental data which were

found to be affected mainly by the microwave power level followed by sample thickness while

system pressure had a little effect on the drying rate. Rehydration ratio was significantly affected

by the system pressure. Empirical models were also developed for estimating the drying rate

constant and rehydration ratio as a function of the microwave-vacuum drying process

parameters.

Srivastava et al. (2009) explained the effects of blanching methods on the drying kinetics of

Oyster mushroom. In this study, Oyster mushroom was treated with hot water and steam

blanching prior to drying in cabinet dryer. A hot air cabinet dryer was used for drying mushroom

at 40, 50, 60, 70 and 80°C temperatures. Solid loss was observed to be 25.46% and 3.32% (wb)

during hot water and steam blanching, respectively. Highest drying rate was observed for hot

water blanched mushroom followed by unblanched and steam blanched mushroom. This leads to

more drying time for the steam blanched mushroom followed by the unblanched and hot water

blanched mushroom for the same level of drying. The drying data was modeled for exponential


-8-

and Page's drying model. Page's model was found to be better than the exponential model for the

prediction of drying rate. The value of the model parameters of the exponential model was found

to be higher than that of Page's model. The effective moisture diffusivity (De) was determined at

different temperatures and found to be maximum for the hot water blanched mushroom and

minimum for the steam blanched mushroom. The effective moisture diffusivity (De) increased

with increase in temperature. The activation energy of hot water blanched, unblanched and steam

blanched mushroom was estimated to be 25.324, 17.113 and 21.165 kJ/mol, respectively.

Lombrana et al. (2010) studied the drying of sliced mushroom by microwave energy for different

operational conditions related to temperature control position and pressure and their effects on

drying kinetics and quality. Thinly sliced mushrooms were dried in a guide cavity by applying

microwave energy at 2.45 GHz. The influence on the quality of the dehydrated mushrooms was

studied by two different techniques: sorption isotherms (Halsey and B.E.T. equations) and

scanning electron microscopy (SEM). Drying kinetics was also analyzed through the

determination of diffusivity by applying a mathematical model that takes into account changes in

moisture on the product surface during the process. Thus, the results of SEM observations and

quality can be linked with diffusivity values in each experiment. As a rule, the operational

conditions imposed result in contrary tendencies in quality and drying kinetics. High heat levels

usually lead to unfavorable quality results in the dehydrated product if not corrected with a

favorable inverse temperature gradient characteristic of microwave heating.

Zecchi et al. (2011) studied on the modeling and minimizing of the combined convective and

vacuum drying process of Parsley and Mushroom. The highest temperature assayed in this study,

at which drying could be performed without appreciable visual damage was 450C for parsley and

550C for mushrooms. For parsley, an important reduction of process time was achieved when

convective and vacuum drying at the maximum suitable drying temperature (450C) was

combined. For mushrooms, when drying was performed at the maximum temperature the most

appropriate technology was the dehydration process in a convective dryer, because the reversion

of the processes’ rates did not occur for this product and temperature.

2.6 Ragi

Nirmala et al. (2000) studied on a recently released hybrid ragi, Indaf-15. It was germinated up

to 96 h at 25 and the sprouts, drawn at 24 h intervals, were dried, devegetated, powdered and

evaluated for malting loss, reducing sugar, free sugar profile, starch content, dietary fiber and an

array of carbohydrate-degrading enzymes. Malting loss was maximum (32.5%) at 96 h. The total

reducing sugar content increased from 1.44 to 8.36%, whereas the total carbohydrate content

decreased from 81 to 58% at 96 h of germination. Analysis of 70% alcohol- soluble sugars

revealed glucose, fructose and sucrose in different proportions with respect to germination time.


-9-

Maltose and mal- totriose were detected after 48 and 72 h, respectively. There was a linear

decrease in starch content (from 65 to 43%). Activities of amylase and pullulanase were

maximum at 72 h whereas those of a-d-glucosidase and 1,3-b-d-glucanase, were maximum at 48

h. Xylanase activity was maximum at 96 h with a concomitant decrease in arabinose to xylose

ratio from 1:1 to 1:0.38 in the dietary fiber. a-Galactosidase activity was negligible, which is in

tune with a very small amount of raffinose series oligosaccharides. The above results indicated

that Indaf-15 is a potential variety for malting purposes as it develops high levels of amylases

during germination, and its malt form is a rich source of reducing sugar.

Subba Rao, and Muralikrishna (2001) studied the nature of non-starch polysaccharides (NSP)

and bound phenolic acids from native and malted ragi using a recently- released hybrid variety of

ragi, (Indaf-15). Yields of water-soluble NSP, hemicellulose-B and cellulose polysaccharides

increased upon malting whereas a substantial decrease in the yield of hemicellulose-A was

observed. Hemicellulose-B is the most viscogenic and its relative viscosity decreased from 3.04

to 1.98 upon 96 h of malting, whereas the solubility and viscosities of the rest of the NSP

increased upon malting. The major sugars identified in all the NSP fractions were arabinose,

xylose, galactose and glucose. A one- to two-fold decrease in arabinose was observed in all the

NSP upon malting except for the alkali-insoluble residue wherein a decrease of glucose was

observed. A progressive decrease in the pentose to hexose ratio was observed, indicating mainly

pentosan degradation during malting, whereas an increase in the pentose to hexose ratio was

observed in the alkaline-insoluble residue (AIR). Ferulic, ca eic and coumaric acids were

identified as the major bound phenolic acids in native ragi and one- to two-fold decrease was

observed in their contents after 4 days of malting.

2.7 Barley

Lyly et al. (2004) studied the effect of concentration and molecular weight of two oat and one

barley b-glucan preparation on the perceived sensory quality of a ready-to-eat soup prototype

before andafter freezing. Oat1 was a bran-type preparation containing high molecular weight b-

glucan; Oat2 and Barley were more processed and purified preparations with lower molecular

weight. Nine soups containing 0.25–2.0 g b-glucan/100 g soup and one reference soup thickened

with starch were profiled by a sensory panel and their viscosity and molecular weight of b-

glucan was analyzed. Freezing had no notable effects on the sensory quality of the soups. At the

same concentration, soups made with the bran-type preparation were more viscous and had

higher perceived thickness than soups made with processed, low molecular weight preparations.

Barley soups had mainly higher flavour intensities than oat soups. Good correlations were

obtained between sensory texture attributes and viscosity (r=0.70–0.84; Pp0.001) and moderate

correlations between flavour attributes and viscosity �(r= 0.63–�0.80; Pp0.001).

Technologically, b-glucans are feasible thickening agent alternatives in soups. Preparations with


-10-

lower molecular weight and viscosity are easier to add into a food product in higher quantities,

but the role of high molecular weight b-glucan in physiological functionality has to be kept in

mind.

2.8 Extrusion process

Rinaldi et al. (1995) found that okara is the residue left after soymilk or tofu production and used

either as animal feed, fertilizer, or landfill. The purpose of this study was to use wet okara to

produce and enrich extruded cereal products and to study the effects of extrusion on the dietary

fiber and isoflavone contents. Wet okara was combined with soft wheat flour to produce two

different formulations (33.3 and 40% okara) and extruded using four combinations of two screw

configurations and two temperature profiles. Various physicochemical properties were analyzed.

The radial expansion ratio decreased as fiber content increased. On the other hand, both bulk

density and breaking strength increased as fiber content increased. Combining okara with soft

wheat flour resulted in increased protein, dietary fiber, and isoflavone contents compared with

soft wheat flour alone. Extrusion of the formulations resulted in decreased insoluble fiber and

increased soluble fiber contents of extrudates. Extrusion decreased the total detectable

isoflavones and altered the distribution of the six detected isoflavones. The overall results

indicate that by using a novel twin-screw extrusion process to cook, sterilize, and remove the

major portion of water, wet okara can successfully be used to make and enrich extruded

products.

Pansawat et al. (2008) concluded that increasing feed moisture and screw speed decreased

pressure at the die. Increased screw speed increased product temperature at the die but

increased feed moisture lowered it. Increased barrel temperature, feed moisture and screw

speed decreased motor torque. Increased screw speed increased specific mechanical energy,

while increased feed moisture reduced it. Longer mean residence times were observed at lower

screw speeds. Product density increased as feed moisture increased, but decreased with screw

speed. Increased feed moisture decreased radial expansion.

Valentina et al. (2009) investigated the effect of different levels of feed moisture (12-17%)

during extrusion cooking; using a co-rotating twin-screw extruder on selected nutritional and

physical properties of extruded products. Four different formulations were used based on wheat

flour and corn starch with the addition of 10% brewer’s spent grain (BSG) and red cabbage (RC)

trimming reducing the flour and starch. The samples were: wheat flour + BSG (WBSG), corn

starch + BSG (CBSG), wheat flour + red cabbage (WRC) and corn starch + red cabbage (CRC).

Process conditions utilized were: constant feed rate of 25 kg/h, screw speed 200 rpm and barrel

temperature of 80 and 120° C. The results indicated that increasing the water feed to 15%

increased the level of total dietary fiber (TDF) in all the extrudates. Extrusion cooking increased


-11-

the level of total antioxidant capacity (TAC) and total phenolic compounds (TPC) in WRC and

CRC. In addition to water feed level affecting the TDF of the extrudates, also affected were the

expansion ratio, bulk density, hardness, WSI, SME and colour. The protein level of the products

and hardness of extrudates were related to the different formulations.

Kumar et al. (2010) investigate with rice flour in different proportions (10-30%) to dehydrated

carrot pomace and pulse powder (CPPP) mixture having equal ratio. The formulation was

extruded at different moisture content (17-21%), screw speed (270-310 rpm) and die temperature

(110-130° C). The lateral expansion, bulk density, water absorption index, water solubility index,

hardness and sensory characteristics were measured as responses. Significant regression models

were established with the coefficient of determination, R2 greater than 0.72. The results indicated

that CPPP proportion and moisture content significantly influenced (P<0.10) lateral expansion;

temperature for water absorption index; screw speed and temperature for hardness and screw

speed for sensory score. The compromised optimum condition obtained by numerical integration

for development of extrudates were: CPPP mixture of 16.5% in rice flour, moisture content

19.23%, screw speed 310 rpm and die temperature 110°C. Sensory evaluation revealed that

carrot pomace could be incorporated into ready-to-eat expanded products upto the level of

8.25%.

2.9 Response Surface Method and Optimization Technique

RSM is a statistical procedure frequently used for optimization studies. It uses quantitative data

from an appropriate experimental design to determine and simultaneously solve multivariate

problems. RSM designs help in quantifying the relationships between one or more measured

responses and the vital input factors. The response surface method produces a mathematical

model that can be used to predict a response. The model equation describes the effect of the

test variables on the responses, determine interrelationships among test variables and represent

the combined effect of all test variables in the response. This approach enables an experimenter

to make efficient exploration of a process or system. Optimization of any process is searching

for a combination of factor levels that simultaneously satisfy the requirements of each of the

responses and factors. Simultaneous optimization of multiple responses can be performed

graphically or numerically.

Response surface methodology (RSM) explores the relationships between several explanatory

variables and one or more response variables. The method was introduced by Box and Wilson

(1951). RSM (Box and Hunter, 1957) is used to optimize the parameters based on several

responses.

Rotatable Central composite design (RCCD) is a response surface methodology for fitting a

second order model to a data set without the use of a complete 3k factorial experiment (Myers,

1971). After the necessary experimental data is created, multiple linear regressions are


-12-

performed. Coded variables are to be used in this method.

Ainsworth (2004) used Response surface methodology to analyze the effect of screw speed

(220–340 rpm), feed moisture (11.0–15.0%, wet basis) and feed rate (22.0–26.0 kg/h, wet

basis) on the physical properties (i.e., bulk density, expansion, porosity) of a nutritionally

balanced extruded snack food. Regression equations describing the effect of each variable on

the responses were obtained. Responses were most affected by changes in screw speed

followed by feed moisture and feed rate (P<0.05).Expansion and porosity increased with screw

speed and feed moisture whereas the opposite was observed for bulk density. Radial expansion

was found to be a better index to measure the extent of expansion than the axial and overall

expansions, indicated by a higher correlation coefficient.

Ozer et al. (2004) used response surface methodology (central composite design) to analyze the

effect of screw speed (220-340 rpm), feed moisture (11-15% wb) and feed rate (22-26 kg/h) on

the physical properties (i.e., bulk density, expansion, porosity) of a nutritionally balanced

extruded snack food. Regression equations describing the effect of each variable on the

responses were obtained.

Pansawat et al. (2008) used RSM to study the effects of extrusion conditions (temperature,

screw speed and feed moisture) on secondary extrusion variables (product temperature,

pressure at the die, motor torque, specific mechanical energy input and mean residence time

and physical properties of the extrudate. Fractional factorial design was used in RSM study.

RSM is an empirical statistical modeling technique employed for multiple regression analysis

using quantitative data obtained from properly designed experiments to solve multivariable

equations simultaneously.

The main idea of RSM is to use a sequential experimental procedure to obtain an optimal

response. An easy way to estimate a first-degree polynomial model is to use a factorial

experiment or a fractional factorial design. This is sufficient to determine which explanatory

variables have an impact on the response variables of interest. Once it is suspected that only

significant explanatory variables are left, and then a more complicated design, such as a central

composite design can be implemented to estimate a second-degree polynomial model, which is

still only an approximation at best. However, the second-degree model can be used to optimize

(maximize, minimize, or attain a specific target for) a response.


-13-

CHAPTER III

MATERIALS AND METHODS

In this chapter the description of raw materials used and the methodology adopted for conducting

various experiments for the extrusion of mushroom powder using twin screw extruder are

presented.

3.1 Raw Materials

3.1.1 Mushroom:

Raw oyster mushrooms were collected from the local market. It was washed with distilled water

and the extra water was drained. The surface moisture was soaked by wrapping the mushroom

with blotting paper. The stem parts were removed.

3.1.2 Hot Water Blanching of Mushroom

The washed mushrooms were hot water blanched. Hot water blanching method was chosen for

pretreatment because this process minimizes the drying time for mushrooms (Srivastava et al,

2009). At first, the washed mushrooms were wrapped in a Maslin cloth. Then the cloth was

immersed in the boiling water (100±5oC) and hold for 2 minutes. Then it was immediately

immersed in the chilled water. The extra water was drained by spreading on perforated

containers. The hot water blanching process of raw mushroom is shown in Fig 3.1

3.1.3 Drying of the mushrooms:

The drying of the mushroom was done in an convective hot air oven. The known quantities of

sample was loaded in perforated trays covered with filter papers in the oven by noting initial

weights and subjected to drying at 55±2oC. The initial temperature was maintained at 55oC for 1

h and then gradually was raised to maintain at 60±2oC till complete drying. The desired moisture

content of the dried sample was 10-12%. The hot air oven is shown in Fig 3.2.

3.1.4 Preparation of Powder:

The dried mushrooms were taken out from the dryer. Then the dried mushrooms were ground in

a laboratory mixer grinder. Then the yield was taken out from the mixer grinder and manually

ground in a hand mortar. The product was treated in a BS 25 sieve. The yield was approximately

80-85%. The powder thus obtained was packed in LDPE pouches and stored at 4oC.


-14-

(a) (b)

(c)

Fig 3.1 Hot water blanching process of mushroom (a) Raw mushrooms

(b) Hot water blanching and (c) immersing in cold water

3.1.4 Ragi and Barley Flour

The ragi and Barley flour were purchased from the local market. They were treated in the same

sieve (BS 25). The yield was approximately 80-85% for both flours. Then each flour was packed

in LDPE pouches and stored at 4oC for future use.


-15-

Fig 3.2 Hot Air Oven Drier for drying of Oyster Mushrooms

3.2 Sample preparation

The mushroom powder and ragi and barley flour mixture were mixed in desired proportion in a

food processor with mixer attachment. The moisture content of the formulation was estimated by

hot air oven method (Ranganna, 1997). The moisture was adjusted by sprinkling distilled water

in dry ingredients. The mixture was then passed through a 2 mm sieve to reduce the number of

lumps formed due to addition of moisture. After mixing, samples were stored in LDPE pouches

at room temperature for 24 h. The whole process has been shown in Fig 3.3


-16-

3.3 Determination of Proximate Composition

Proximate compositions and nutritional properties of final products namely, moisture content,

protein, fat, crude fir content, carbohydrates, ash content required for the present investigation

were determined.

3.3.1 Moisture content

The moisture content of the final product was determined by hot air oven method as descrid by

Ranganna (1997). Weighed test sample (5g approx.) was kept in duplicate in hot air electric

oven at a temperature of 100±5°C for 24 h, after which it was kept inside a desiccators for

cooling to ambient temperature and the change in weight was noted. The moisture content was

expressed either in percent (wet basis) or kg moisture/kg dry matter (dry basis).

3.3.2 Fat content

Fat soluble material in a food was extracted from an oven-dried sample using a Soxhlet

extraction apparatus. The either or hexane was evaporated and the residue weighed.

Wt. of fat soluble materialFat content 100

Wt.of sample

3.3.3 Ash content and Crude Fiber content

It was determined according to AOAC (1984) method.


-17-

Fig 3.3 Flow chart of the Process.

Raw Mushrooms

Washed under

Flowing Water

Hot Water

Blanching at

100±5 0C

Drying at 55 0C

Preparation of

Mushroom Powder

Preparation of

Mushroom Powder

Blend Preparation

with Ragi and

Barley Flour

Extrusion of Blend

Measurement of

Responses


-18-

3.3.4 Protein content determination

Protein content was estimated from the crude nitrogen content of the sample determined by the

Kjeldahl method (N ×6.25), (AOAC, 1984).The digester, scrubr and dwastillation unit are shown

in Fig. 3.4 and Fig. 3.5 respectively.

Fig. 3.4 IR Digester Unit K-435 and Scrubr B-414.

Fig. 3.5 Dwastillation units (K-360).

3.3.5 Carbohydrates (by difference method)

The carbohydrate content was estimated by subtracting the values of moisture, protein, ash,

crude fat and crude fiber from 100.


-19-

3.4 Extruder

The extruder used for this experimental purpose was BTPL make laboratory co-rotating twin-

screw extruder (EB-10 model) having L/D ratio of 14.4:1. The extruder was pre-assembled and

skid-mounted and placed on 3” raised platform. Raised platform helps cleaning beneath the

extruder. The extruder has shown in Fig. 3.6.

Fig.3.6 BTPL Lab Model (EB-10) Twin Screw Extruder.

1.Temperature sensor, 2.Heater, 3.Cutter motor, 4.Cutter casing, 5.Water circulation

pipe, 6.Feeder hopper, 7.Feeder motor, 8.Extruder motor, 9.Gear box, 10.Inching

and emergency stop button, 11.Barrel

3.4.1 Drive system

The main drive was provided with 10 hp motor (400 V, 3 ph, 50 Hz). It was provided with

SIEMENS / ABB. Frequency drive to control the rpm precisely according to the need of the

process. The output shaft of worm reduction gear was provided with a torque limiter coupling

consisting of torque limiter and roller chain type coupling. The torque limiter was a protective

device that limits torque transmitted by output shaft of worm reduction gear.

3.4.2 Extruder barrel

The barrel of extruder receives feed from co-rotating feeder fitted with Siemens make

frequency controller for obtaining variable speed. The barrel consists of two parallel co-

6.

7.

8.

9.

10.

11.

1.

2.

3.

4.

5.


-20-

rotating screws driven by drive assembly. These screw lead material form feeding zone to die.

The co-rotating screws were of intermeshing types and as they rotate in the same direction, it

helps in self cleaning of screws. The twin screw assembly has shown in Fig. 3.8.

Fig. 3.7 Control panel for Twin screw extruder.

Fig. 3.8 Twin screw in head assembly. Fig. 3.9 Extruder die assembly.


-21-

3.4.3 Feeder

The barrel of extruder receives the feed from a co-rotating feeder. The rated capacity of the

feeder was controlled by knob on control panel. The calibration chart was prepared for reading

feed rate in terms of flow rate in kg/h.

3.4.4 Heating arrangement

The extruder barrel was provided with three electric band-heaters (just fore die section,

kneading section and feeding section). The temperature sensors were fitted at each of three

sections, which were connected to temperature controller and digital output on control panel.

3.4.5 Extruder die

The die plate of die (either solid or split) fixed by a screwed nut tighten by a special wrench

provided. Extruder die has shown in Fig. 3.9.

3.4.6 Cutting knife

The automatic cutting knife was fixed on a rotating shaft of knife drive assembly. The cutter

was drive by a variable speed AC motor and it was controlled by frequency controller through

a knob provided on control panel. The automatic cutter assembly was covered by a hinged

safety guard.

3.4.7 Panel board

The extruder was provided with stand-alone type control panel. The control panel controls and

shows the extruder screw speed, barrel temperature, feed rate and cutter rpm. An electric

supply main switch (3 ph, 60 A, 400 V, 50 Hz AC) supply with neutral line had provided to

control panel. Control panel has shown in Fig. 3.7.

3.4.8 Water circulation

Three water jackets were connected to extruder barrel with water supply through solenoid

valve controlled through PID controllers. The outlets were connected to a delivery line leading

to outside drain. The water circulation starts when temperature of heaters exceeds desired limit.

3.4.9 Inching

Since, drive system in this extruder generates torque gradually, a bypass switch (installed at the

side of the desk) was provided to directly apply the drive from the motor which gives the

sudden application of torque necessary to clean the barrel from burn-out products. It was

imperative to remove dies fore applying direct drive from motor for inching device from motor

for inching device. This was essentially required to clean jamming in barrel which was a

special feature in this model.


-22-

3.4.10 Emergency stop

The panel board was provided with an emergency stop switch. It should switched-off in case of

emergency such as entry of foreign object inside barrel.

3.5 Water Absorption Index (WAI) and Water Solubility Index (WSI)

The water absorption index (WAI) an indicator of the sample to absorb water, depends on the

availability of hydrophilic group which bind water molecules and on the gel forming capacity

of macromolecules measures the volume occupied by the granule or starch polymer after

swelling in excess of water. While water solubility index (WSI) was used as a measure for

starch degradation; it means that at lower WSI there was minor starch degradation of starch

and such condition leads to less numbers of soluble molecules in the extruded.

WAI and WSI were determined by the method of Anderson (1982). The extruded products

were milled to a mean particle size of 200–250 µm. A 2.5 g sample was dispersed in 25 g

distilled water, using a glass rod to break up any lumps and then stirred for 30 min at room

temperature. The dispersions were rinsed into tarred centrifuge machine, made up to 32.5 g and

then centrifuged at 2740 g (4000 rpm) for 15 min. The supernatant was decanted for

determination of its solid content and sediment was weighed. WAI and WSI were calculated

as:

Weight gain by gel

WAI = Dry weight of extrudte

WSI = X 100

3.8 Texture (Hardness)

The texture characteristics of extruded mushroom products and hardness were measured using

a stable micro system TA-XT2 texture analyzer (Texture Technology corp., UK) fitted with a

25 mm cylinder probs. The studies were conducted at a pre test speed of 1.0 mm/s, test speed

of 0.5 mm/s post test speed of 10 mm/s, distance of 30% strain, and load cell of 5 kg.

Hardness value was considered as mean peak compression force and expressed in grams.

Average values of five replications were considered Fig.3.9 shows a typical force time curve of

Mushroom Powder based extruded products for hardness measurement.


-23-

Fig. 3.10 A typical force-time curve of Mushroom Powder based extruded products for texture

measurement.

3.9 Experimental Procedure

Response surface methodology (RSM) was adopted in the design of experimental combinations.

The main advantage of RSM was the reduced number of experimental runs needed to provide

sufficient information for statistically acceptable results. A three-variable (five levels of each

variable) rotatable central composite experimental design was employed .The parameters and

their levels were chosen based on the literature available on extrusion process. The ingredients

used for the mushroom powder based extruded products preparation were dried mushroom

powder, ragi flour and barley flour. The five levels of the process variables were coded as -1.682,

-1, 0, +1, +1.682 (Montgomery, 2001) and design in coded form and at the actual levels are

given in Table 3.1.

3.10.1 Independent process variables

The independent variables considered during the experiment were:

1. Barrel temperature - 80o to 120o C

2. Screw speed - 200 to 300 rpm

3. Mushroom powder level – 0% to 20 %

The die size of 3 mm kept constant. Also the temperature of feeding zone and

kneading zone kept constant at 60o C and 80o C, respectively throughout the


-24-

experiments.

3.10.2 Dependent process variables

The dependent variables considered during the experiment were:

1. Water solubility index (WSI)

2. Water absorption index (WAI)

3. Hardness (Hd)

3.10.3 Experimental design

Experiments were conducted in rotatable central composite design (RCCD) with four variable

and five levels of each variable. The process variables were barrel temperature, screw speed,

and dried mushroom powder level. With 6 numbers of central point experiment total number of

experiment was 20. Their corresponding ranges with details of actual and coded values are

given in Table 3.1.

3.11 Optimization

The Experimental design was applied after selection of the ranges. Twenty experiments were

performed according to a second order rotatable central composite design (RCCD) with three

variables and five levels of each variable. RSM was applied to the experimental data using a

commercial statistical package, Design Expert-version 8.0.2 (Stat-Ease, Minneapolwas, USA).

The twin screw extrusion process was optimized. The responses studied were Water Solubility

Index (WSI), Water Absorption Index (WAI) and Hardness (H).

The following second order polynomial response surface model was fitted to each of the

response:

2 2 2

21 1 1

k k o k i i k i i i k i j i ji i i j

Y b b X b X b X X

i=1, 2, 3; j=1,2

Where, Yk was response, bk, bki, bkii, and bkij are the constant, linear, quadratic and interaction

coefficients respectively and X1, X2 and X3 are codes of variables viz., apple pomace level,

moisture content of the raw material, screw rpm and barrel temperature respectively.

All the process variable variables were optimized for maximum water absorption index (WAI),

Minimum water solubility index (WSI) and minimum Hardness (H). The superior (optimum)

combination of the barrel temperature, screw rpm and mushroom powder level were selected

for the production of optimized mushroom powder based extruded products and the estimation


-25-

of proximate composition viz., protein, fat, fir and carbohydrate content.

Table 3.1 Experimental combination for five different operating conditions (Actual values)

Run Barrel Temperature

(oC)

Screw Speed (rpm) Mushroom Powder

(%)

1 80.00 250 10

2 88.11 220.27 4.05

3 111.89 220.27 15.95

4 111.89 279.73 4.05

5 88.11 279.73 4.05

6 88.11 279.73 15.95

7 100.00 250.00 10.00

8 100.00 250.00 10.00

9 100.00 250.00 10.00

10 100.00 200.00 10.00

11 100.00 250.00 10.00

12 111.89 279.73 15.95

13 111.89 220.27 4.05

14 100.00 250.00 20.00

15 88.11 220.27 15.95

16 100.00 250.00 0.00

17 120.00 250.00 10.00

18 100.00 300.00 10.00

19 100.00 250.00 10.00

20 100.00 250.00 10.00


-26-

Table 3.2 Experimental combination for five different operating conditions (Coded values)

Run Barrel Temperature

(oC)

Screw Speed (rpm) Mushroom Powder (%)

1 80.00 250 10

2 88.11 220.27 4.05

3 111.89 220.27 15.95

4 111.89 279.73 4.05

5 88.11 279.73 4.05

6 88.11 279.73 15.95

7 100.00 250.00 10.00

8 100.00 250.00 10.00

9 100.00 250.00 10.00

10 100.00 200.00 10.00

11 100.00 250.00 10.00

12 111.89 279.73 15.95

13 111.89 220.27 4.05

14 100.00 250.00 20.00

15 88.11 220.27 15.95

16 100.00 250.00 0.00

17 120.00 250.00 10.00

18 100.00 300.00 10.00

19 100.00 250.00 10.00

20 100.00 250.00 10.00


-27-

CHAPTER IV

RESULTS AND DISCUSSION

In this chapter the results of different experiments conducted are presented under various

sections. These sections include results of proximate analyses of raw materials, and mushroom

powder based extrusion products using Twin Screw Extruder. Results of quality evaluation viz.

Water Solubility Index (WSI), Water Absorption Index (WAI) and hardness are also reported

in this chapter.

4.1 Proximate Analysis of Raw Materials

Proximate analysis of raw materials was done by the methods described in the section 3.2 of

chapter 3 and results are shown in Table 4.1.

Table 4.1 Proximate composition of ingredients of mushroom powder based extrudate products

per 100 g weight

Parameters Mushroom

Powder

Barley

Flour

Ragi

Flour

M.C. (%wb) 10.8 7.01 7.61

Protein content, (%) 23.89 9.9 6.76

Fat, (%) 2.7 2.9 1.88

Crude Fibre, (%) 29.22 12.01 2.52

Carbohydrates, (%) 41.1 67.06 78.76

Ash content, (%) 7.44 1.3 2.24

4.2 Properties of Extruded

Variation of responses (water absorption index, water solubility index, hardness) of extruded

with independent variables (mushroom powder content, screw speed and barrel temperature) is

shown in Table 4.2 and 4.3.

.


-28-

Table 4.2 Different physical properties of extruded under different operating conditions (actual values)

Run Barrel

Temperature

(oC)

Screw

Speed

(rpm)

Mushroom

Powder

(%)

WAI

(g/g)

WSI

(%)

Hardness

(kg-f)

1 80.00 250.00 10.00 6.1 2.52 5.43

2 88.11 220.27 4.05 6.0788 6.04 6.18

3 111.89 220.27 15.95 12.443 8.8 5.9

4 111.89 279.73 4.05 7.268 4.04 4.078

5 88.11 279.73 4.05 7.268 7.417 4.23

6 88.11 279.73 15.95 13.224 5.32 6.91

7 100.00 250.00 10.00 8.172 4.9 5.93

8 100.00 250.00 10.00 4.5816 4.8 5.39

9 100.00 250.00 10.00 9.223 3.8 4.43

10 100.00 200.00 10.00 4.389 6.8 5.13

11 100.00 250.00 10.00 4.406 6.0 5.1

12 111.89 279.73 15.95 15.34 6.09 7.55

13 111.89 220.27 4.05 6.628 6.5 3.89

14 100.00 250.00 20.00 20.003 9.56 7.58

15 88.11 220.27 15.95 13.224 6.42 6.52

16 100.00 250.00 0.00 8.339 11.02 3.33

17 120.00 250.00 10.00 5.732 2.72 5.66

18 100.00 300.00 10.00 5.808 4.0 5.152

19 100.00 250.00 10.00 6.229 4.4 4.87

20 100.00 250.00 10.00 4.6632 5.1 5.21


-29-

Table 4.3 Different physical properties of extruded under different operating conditions (actual values)

Run Barrel

Temperature

(oC)

Screw

Speed

(rpm)

Mushroom

Powder

(%)

WAI

(g/g)

WSI

(%)

Hardness

(kg-f)

1 80.00 250.00 10.00 6.1 2.52 5.43

2 88.11 220.27 4.05 6.0788 6.04 6.18

3 111.89 220.27 15.95 12.443 8.8 5.9

4 111.89 279.73 4.05 7.268 4.04 4.078

5 88.11 279.73 4.05 7.268 7.417 4.23

6 88.11 279.73 15.95 13.224 5.32 6.91

7 100.00 250.00 10.00 8.172 4.9 5.93

8 100.00 250.00 10.00 4.5816 4.8 5.39

9 100.00 250.00 10.00 9.223 3.8 4.43

10 100.00 200.00 10.00 4.389 6.8 5.13

11 100.00 250.00 10.00 4.406 6.0 5.1

12 111.89 279.73 15.95 15.34 6.09 7.55

13 111.89 220.27 4.05 6.628 6.5 3.89

14 100.00 250.00 20.00 20.003 9.56 7.58

15 88.11 220.27 15.95 13.224 6.42 6.52

16 100.00 250.00 0.00 8.339 11.02 3.33

17 120.00 250.00 10.00 5.732 2.72 5.66

18 100.00 300.00 10.00 5.808 4.0 5.152

19 100.00 250.00 10.00 6.229 4.4 4.87

20 100.00 250.00 10.00 4.6632 5.1 5.21


-30-

Table 4.4 Minimum and Maximum values of the responses

Response Name

Units Observations Minimum Maximum

Y1 WAI g/g 20 4.389 20.003

Y2 WSI % 20 2.52 11.02

Y3 Hardness Kg-f 20 3.33

7.58

4.3 Diagnostic Checking of the Fitted Model

Based on t-statistics, regression coefficients significant at 90% level were selected for

developing the models representing the final equations in terms of coded factors. The resulting

polynomial, after removing the non-significant terms and all model term values, was calculated

and is presented in Table 4.5. Regression analyses showed that Hardness was significantly (P <

0.05) affected by linear term of C and interaction terms of (AB and BC. WSI was affected by

linear term of (B), interaction terms of (AB , AC) and quadratic terms of ( A2 and C2 ) , and WAI

was influenced by linear term of (C) and quadratic term of ( C2 ).

Table 4.4 The coded regression models for process variables and product properties: Water

Absorption Index (A), Water Solubility Index (B) and Mushroom powder level (C):

Responses Equation R2 R2 Adj.

F-value

Y1

WAI = + 6.16 + 0.093 * A + 0.52 * B + 3.41* C + 0.29 * A * B + 0.098 * A * C + 0.13 * B * C + 0.24 * A2 - 0.045

* B2 + 3.17 * C2 ……..(4.1)

0.9065

0.8224

10.78

Y2

WSI = + 4.83 + 0.042 * A - 0.70 * B + 0.013 * C - 0.68

*A * B + 0.76 * A * C - 0.34 * B * C - 0.75 * A2 + 0.23 *

B2 + 1.96 * C2 ….(4.2)

0.9392

0.8846

17.18

Y3

Hardness = + 15 - 0.15 * A + 0.023* B + 1.15 * C + 0.42 * A * B + 0.31* A * C + 0.48 * B * C + 0.19 * A2 + 0.051 * B2 + 0.16 * C2 ……….(4.3)

0.9137

0.8361

11.77


-31-

4.4 Analysis of Variance (ANOVA)

The goodness-of-fit of the models was evaluated using the correlation coefficient R2, the R2

adjusted. (Piggot, 1986), the Fisher F test, as well as the derived P values and the results are

presented in Tables 4.5, respectively. In addition, significance of the lack of fit term was used to

judge adequacy of model fit. Regression models fitted to experimental results showed good

correlation coefficients (> 90%) for all extruded properties. For a response surface, these

correlation coefficients were quite high (Box et al., 1978). Table 4.5 shows that the F-values for

Y1, Y2 and Y3 were significant at the 95% level. However, the lack of fit was not significant for

Y1, Y2 and Y3 (P < 0.05).

Table 4.5 Analysis of variance (ANOVA) for second-order polynomial model fitted to response

surface

Response source Df.* SS MS F-

Value

P-Value

Prob>F

Y1

Model 9 309.91 34.43 10.77 0.0005

significant

A

B

C

A2

B2

C2

AB

AC

BC

1

1

1

1

1

1

1

1

1

0.12

3.70

159.04

0.69

0.077

0.14

0.86

0.029

144.26

0.12

3.70

159.04

0.69

0.077

0.14

0.86

0.029

144.26

0.037

1.16

49.78

0.22

0.024

0.045

0.27

8.936E-003

45.09

0.8519

0.306

<0.0001

0.6523

0.8796

0.8370

0.6157

0.9256

<

0.0001

Residual 10 31.95 3.20

Lack of

Fit

5 10.72 2.14 0.51 0.7642 Not

significant

Pure

Error

5 21.23 4.25


-32-


Value

P-Value

Prob>F

Cor Total 341.87 19

significant

Y2

Model 9 84.65 9.41 17.18 <0.0001

A

B

C

A2

B2

C2

AB

AC

BC

1

1

1

1

1

1

1

1

1

1

0.024

6.75

2.353E-003

3.71

4.60

0.93

8.15

0.77

55.39

0.024

6.75

2.353E-

003

3.71

4.60

0.93

8.15

0.77

55.39

0.043

12.33

4.298E-003

6.77

8.40

1.70

14.88

1.40

101.16

0.8392

0.0056

0.9490

0.0264

0.0159

0.2218

0.0032

0.2633

<

0.0001

Residual 10 5.48 0.55

Lack of

Fit

5 2.78 0.56 Not

significant

Pure

Error

5 2.69 0.54

Cor Total 19 90.13

Model 9 23.09 2.57 11.77 0.0003

A

B

C

A2

B2

1

1

1

1

1

0.30

7.266E-003

17.93

1.44

0.30

7.266E-

003

17.93

1.39

0.033

82.27

6.62

0.2655

0.8588

<

0.0001


-33-


Value

P-Value

Prob>F

Y3

C2

AB

AC

BC

1

1

1

1

0.76

1.81

0.54

0.037

0.38

1.44

0.76

1.81

0.54

0.037

0.38

3.48

8.29

2.47

0.17

1.73

0.0277

0.0918

0.0164

0.1469

0.6896

0.2179

significant

Residual 10 2.18 0.22

Lack of

Fit

5 0.910 0.18 0.02 0.6375 Not

significant

Pure

Error

5 1.27 0.23

Cor Total 19 25.27


-34-

4.5 Water Absorption Index (WAI)

It is evident from Eq. (4.1) that Y1 depends on the three factors. All of the terms having positive

coefficient, viz, linear terms A, B and C, interaction terms AB, BC and AC and quadratic terms

A2 and C2 increases the WAI values. Only the quadratic term B2 having a negative coefficient

causes negligible decrease in the values of WAI. WAI measures the volume occupied by the

granule or starch polymer after swelling in excess water (Sriburi & Hill, 2000). It is visible from

the response surface graph that the WAI value increases with the mushroom content. The highest

value of WAI is 20.03 g/g which comes at 20 % mushroom powder level. It so happens due to

the fact that mushroom powder reconstitutes more rapidly. Moisture content, acting as a

plasticizer during extrusion cooking, reduces the degradation of starch granules and results in an

increased capacity for water absorption of cooked product. It is also visible from the response

surface graphs that the WAI increases with increasing screw speed level.

88.11

94.06

100.00

105.94

111.89

220.27

235.13

250.00

264.87

279.73

4.2

5.475

6.75

8.025

9.3

W

AI

A: Barrel Temperature

B: Screw Speed

Fig 4.5(a). Effect of extrusion variables barrel tempereature and screw speed on WAI


-35-

Fig 4.5(b). Effect of extrusion variables barrel tempereature and mushroom powder on WAI

Fig 4.5(c). Effect of extrusion variables screw speed and mushroom powder on WAI

220.27

235.13

250.00

264.87

279.73

4.05

7.03

10.00

12.98

15.95

4

8.25

12.5

16.75

21

WAI

B: Screw Speed C: Mushroom Powder Level

88.11

94.06

100.00

105.94

111.89

4.05

7.03

10.00

12.98

15.95

4

8.25

12.5

16.75

21

WAI

C: Mushroom Powder Level

A: Barrel

Temperature


-36-

4.6 Water Solubility Index (WSI)

The model equation predicting this response is given by Eq. (4.2). The positive linear coefficient

of A and C, quadratic coefficient of C2 and A2 and interaction terms of AC contributed to the

increase of Y4, whereas the negative linear coefficient of B, interaction terms of AB and Ac and

quadratic term of A2 contributed o the decrease of WSI. The highest value, i.e., 11.02% is

obtained at 0% mushroom powder level. The barrel temperature has also a significant effect on

the WSI values. It is increased with the increase of barrel temperature. The WSI determines the

amount of free polysaccharide or polysaccharide released from the granule after addition of

excess water. Moisture content for the blend was controlled to 16-17%.

.

Fig 4.6(a). Effect of extrusion variables barrel tempereature and screw speed on WSI

88.11 94.06

100.00 105.94

111.89

220.27

235.13

250.00

264.87

279.73

2.5

3.575

4.65

5.725

6.8

WSI

A: Barrel Temperature B: Screw Speed


-37-

Fig 4.6(b). Effect of extrusion variables barrel temperatureand mushroom powder on WSI

Fig 4.6(c). Effect of extrusion variables screw speed and mushroom powder on WSI

4.05

7.03

10.00

12.98

15.95

88.11

94.06

100.00

105.94

111.89

2.5

4.675

6.85

9.025

11.2

WSI



88.11 94.06

100.00 105.94

111.89

4.05

7.03

10.00

12.98

15.95

2.5

4.675

6.85

9.025

11.2

WSI




-38-

4.7 Hardness

It is evident from Eq. (4.3) that Y3 depends on the three factors. All the linear, interaction and

quadratic factors come with positive coefficients; so they increases the hardness values except

linear term A. It is, due to have a negative coefficient, causes a decrease in hardness values. The

response surface graphs obtained from this model show that the lowest values of hardness were

obtained at 4.05 % mushroom powder level. However, temperature has a very little effect on

hardness. It happens probably due to increase in starch degradation.

Fig 4.7(a). Effect of extrusion variables barrel tempereature and screw speed on Hardness

88.11

94.06

105.94

111.89

220.27

235.13

250.0

264.87

279.73

4.4

4.8

5.2

5.6

6

Hardness

A: Barrel Temperature B: Screw Speed


-39-

Fig 4.7(b). Effect of extrusion variables barrel tempereature and mushroom powder on

Fig 4.7(c). Effect of extrusion variables mushroom powder and screw speed on hardness

4.05

7.03

10.00

12.98 15.95

88.11

94.06

100.00

105.94

111.89

3.3

4.375

5.45

6.525

7.6

Hardness

C: Mushroom Powder Level A: Barrel Temperature

88.11

94.06

100.00

105.94

111.89

4.05

7.03

10.00

12.98

15.95

3.3

4.375

5.45

6.525

7.6

Hardness




-40-

4.12 Optimization and model verification performance

Numerical optimization of the process variables was carried out with the help of commercial

software (Design Expert Version, 8.0.2 trial). The optimization was carried out under certain

applied constraints. The software was used to generate optimum processing conditions and to

predict the corresponding responses as well. The applied constraints and the predicted optimum

values obtained for the various responses are reported in Table 4.6 Extrusion cooking was

carried out under the optimum processing conditions and the responses were recorded (mean of

10 measurements). Thus, establishing the suitability of the models to predict the various

responses as desired for a particular application.

Table 4.6 Optimized processing condition of the variables and responses

Name Condition Lower limit Upper limit Importance

Barrel Temperature is in range 88.11 111.89 3

Screw Speed is in range 220.27 279.73 3

Mushroom Powder

Level maximize 4.05 15.95 3

Responses

WAI maximize 4.389 20.003 3

WSI minimize 2.52 11.02 3

hardness minimize 3.33 7.58 3


-41-

Table 4.7 Optimized values of the independent parameters

No

Barrel

Temperature

Screw

Speed

Mushroom

Powder

Level WAI WSI hardness

Desira

bility

1 88.11 257.94 15.78 12.6141 5.08604 6.476101 0.553

2 88.11 257.68 15.78 12.61421 5.08908 6.475742 0.553

3 88.11 257.26 15.8 12.63708 5.10105 6.47822 0.553

4 88.11 256.91 15.87 12.73713 5.13687 6.490993 0.553

5 88.11 255.35 15.87 12.73195

5.1285 6.488024 0.553

4.13 Proximate analysis of the optimized extrudate

The results obtained from proximate analysis of extrudate product prepare according to the

rotatable central composite design are tabulated in Table 4.8.

Table 4.8 Proximate composition of extruded product

Parameter Content (g/100g)

M.C.(g) 7.84

Protein content, (g) 10.19

Fat, (g) 2.34

Crude fiber (g) 6.19

Carbohydrates, (g) 69.54

Ash content, (g) 2.98


-42-

CHAPTER V

SUMMERY AND CONCLUSION

Barley (Hordeum vulgare vulgare L.) is an ancient cereal grain, which upon domestication has

evolved from largely a food grain to a feed and malting grain. However, barley food use today

remains important in some cultures around the world, particularly in Asia and northern Africa,

and there is renewed interest throughout the world in barley food because of its nutritional value.

This review covers basic and general information on barley food use and barley grain processing

for food use, as well as an in-depth look at several major aspects/traits of interest for barley food

use including kernel hardness and colour, grain starch, and β-glucan contents.

Finger millet (Ragi, Eleusine Coracana) is an important staple food in the eastern and central

Africa as well as some parts of India (Majumder et al., 2006). It is rich in protein, iron, calcium,

phosphorus, fibre and vitamin content. The calcium content is higher than all cereals and iodine

content is said to be highest among all the food grains. Ragi has best quality protein along with

the presence of essential amino acids, vitamin A, vitamin B and phosphorus (Gopalan et al.,

2004). Thus ragi is a good source of diet for growing children, expecting women's, old age

people and patients.

Oyster mushroom (Pleurotus ostreatus) is one of the most widely eaten mushrooms. It is rich in

protein and other necessary nutritional components. Consumer demand is also increasing for

mushroom soup. Many mushroom soup powder are available in the market. The dry mushroom

content of these products are approximately 2-3% giving not more than 0.5% protein content in

the soup.

Hence it is intended to use the dried mushroom powder for preparation of protein enriched

product for soup powder preparation using Twin Screw Extruder. Barley and ragi flour increases

the crude fiber content and also effect the texture and solubility of the product. So, barley and

ragi were also used for the extrusion purpose.

The technology of extrusion of foods has grown rapidly in the last 15 years, mainly because it

can economically produce a variety of products with attractive texture, size and shape. The use

of twin screw extruders has rapidly increased the number of extruded products. To utilize this

Twin screw extrusion process effectively, the independent process parameters need to be

optimized on the basis of the product qualities, such as Water absorption index, water

solubility index and texture (hardness) of the final product.

Twin screw extruders have certain advantages over the single screw extruder viz., flexibility,

easy to handle, better control, variability, cheaper production cost/metric ton, almost nil survival

of microbial count.


-43-

The response surface methodology (RSM) was used to optimize the process parameters for

developing RTE snack.

Based on the above considerations the present investigation was undertaken with the following

objectives:

1. To develop protein enriched ingredient for the preparation of mushroom soup powder

using twin screw extruder.

2. To optimize the process parameters for the preparation of the mushroom soup ingredient

A laboratory model co-rotating twin screw extruder (make: BTPL, model: EB-10) with 10 HP

motor (400V, 3 Ph, 50 Hz) was used for extrusion cooking purpose. The extruder barrel was

provided with 3 electric band heater (just before die section, kneading section and feeding

section) and a temperature sensor for each. 3 water jackets were provided to extruder barrel

with water supply through solenoid valves controlled through PID controller.

The independent variables considered during the experiment were:

4. Barrel temperature - 80o to 120o C

5. Screw speed - 200 to 300 rpm

6. Dried mushroom powder added- 0% to 20%

The die size of 3 mm kept constant. Also the temperature of feeding zone and kneading zone

kept constant at 60o C and 80o C, respectively throughout the experiments.

The experimental design was done accordingly to a second order rotatable central composite

design (RCCD) and a total of 20 experiments were performed according to with three variables

and five levels of each variable. RSM was applied to the experimental dada using a

commercial statistical package, Design Expert-version 8.0.2 (Statease Inc., Minneapolis,

USA). The relative effects of the process variable on the responses were studied and the twin

screw extrusion process was optimized in order to get best quality mushroom powder based

extruded product. The responses studied were Water Solubility Index (WSI), Water Absorption

Index (WAI), and Hardness (Hd). The second order polynomial response surface model was

fitted to each of the response.

Product was optimized for maximum Water Solubility Index (WSI), minimum Water

Absorption Index (WAI) and minimum Hardness. Quadratic model was fitted to the

experimental data for all the variables. Numerical optimization of all the responses gave final

solution in terms of variables viz., barrel temperature 88.11°C, screw rpm 257±1.0, mushroom

powder level 15.8%. The corresponding responses predicted were 12.6 g g-1, 5.08 %, and 6.47

kgf for WAI, WSI and Hd respectively. The optimum MP based extruded product having

protein content, fat content, Crude Fiber, carbohydrates and ash content are 10.19, 2.34, 6.19,

69.54 and 2.98 respectively.


-44-

Based on results of the present investigation, following conclusions could be drawn:

1. The optimum conditions for developing protein enriched mushroom powder based

extruded product through Twin Screw Extruder are, flour mix comprised of Barley and

Ragi flour with 15.8% of dried mushroom powder; screw speed of 257±1 rpm and barrel

temperature of 88.11°C.

2. The developed mushroom powder based extruded product is enriched with high protein

content (10.19%) which eventually can increase the total protein content of soup powder.


-45-

FUTURE WORK

1. The hardness of the extruded product can be minimized by using increased moisture

content in the blend. Hence, studies on the effect of varying moisture content during the

extrusion process on hardness can be done.

2. The extruded product developed will be used as an ingredient for the preparation of

mushroom soup powder. Experiments regarding the textural changes of the soup made at

different temperatures with different intervals from the products can be done in future.

3. The sensory evolution of the soup using varying degrees of additives and viscosity analysis

using stabilizers can be done.


-46-

REFERENCES

Adejumo, T. O. and Awosanya, O. B. (2004) Proximate and mineral composition of four edible

mushroom species from South Western Nigeria. African Journal of Biotechnology, 4:

1084-1088

Anderson, R.A., Anderson, H.F., Conway, V.F. and Griffin, E.L. (1969). Gelatinization

of corn grits by roll and extrusion cooking. Cereal Science Today, 14: 4-12.

Anderson, R.A. (1982) Water absorption and solubility and amylograph characteristics of roll-

cooked small grain products. Journal of Cereal Chemistry, 59: 265–269.

Ainsworth, P., Ibanoglu, S., Plunket, A., Ibanoglu, E. and Stojceska,V. (2007). Effect of brewers

spent grain addition and screw speed on the selected physical and nutritional properties of

an extruded snack. Journal of Food Engineering, 81(4): 702–709.

AOAC (1984). Official methods of analysis of the association of official analytical chemists,

Washington, DC, USA.

AOAC. (1990). Official Methods of Analysis of the Association of Official Analytical Chemists,

Vol. II, 15 th ed. Sec.985.29. The Association: Arlington, VA.

Altan, A., McCarthy, K.L., Maskan, M. (2008). Evaluation of snack foods from barley–tomato

pomace blends by extrusion processing. Journal of Food Engineering, 84: 231–242.

Box, G.E.P. and Wilson, K.B. (1951). On the experimental attainment of optimum conditions.

Journal of the Royal Statistical Society, 13(1): 1-45.

Box, G.E.P. and Hunter, J.S. (1957). Multi-factor experimental designs for exploring responses.

Annals of Mathematical Statistics, 28: 195-241.

Box, G.E.P. Hunter, W.G. and Hunter, J. S. (1978). Statistics for Experimenters. John Wiley &

Sons, New York, USA, pp. 653.

Bergstrom, A. (2006). Enzymatic pre-treatment of Shiitake mushroom. Examensarbete. 248.

Brennan, M., Port, G.L., and Gormley, R. (2000). Post-harvest Treatment with Citric Acid or

Hydrogen Peroxide to Extend the Shelf Life of Fresh Sliced Mushrooms. Lebensm.-Wiss.

u.-Technol. 33: 285-289

Chen, H. C. and Chen, C. S. (1974) Effects of Dehydration on Volume Contraction in Mushrooms.

J. agric. Engng Res.,19: 97-99.

Kumar, N., Sarkar, B. C. and Sharma. H. K. (2010). Development and characterization of extruded

product of carrot pomace, rice flour and pulse powder. African Journal of Food Science, 4:

703 – 717.u


-47-

Lombraña, J.I., Rodríguez, R and Ruiz, U. (2010). Microwave-drying of sliced mushroom. Analysis

of temperature control and pressure. Innovative Food Science and Emerging Technologies,

11: 652–660

Lyly, M., Marttila, M.S., Suortti, T., Autio, K., Poutanen, K., Lahteenmaki., L. (2004). The sensory

characteristics andrheologica l properties of soups containing oat and barley b-glucan

before and after freezing. Lebensm.-Wiss. u.-Technol. 37: 749–761

Myers, R.H. (1971). Response Surface Methodology. Allyn and Bacon, Inc., Boston.

Nirmala, M., Subba Rao, M.V.S.S.T. and Muralikrishna, G. (2000). Carbohydrates and their

degrading enzymes from native and malted finger millet (Ragi, Eleusine coracana, Indaf-

15). Food Chemistry 69: 175-180.

Ozer, E. A. Ibanoglu, S., Ainsworth, P. and Yagmur, C. (2004). Expansion characteristics of a

nutritious extruded snack food using response surface methodology. Journal of European

Food Research and Technology, 218: 474–479.

Pansawat, N., Jangchuda, K., Jangchuda, A., Wuttijumnonga, P., Saaliac, F.K., Eitenmillerb, R.R.

and Phillipsc, R.D. (2008). Effects of extrusion conditions on secondary extrusion

variables and physical properties of fish, rice-based snacks. LWT-Food Science and

Technology, 41(4): 632-641.

Prasad, S. and Giri, S.K. (2007). Drying kinetics and rehydration characteristics of microwave-

vacuum and convective hot-air dried mushrooms. Journal of Food Engineering, 78: 512–

521

Rossen, J.L. and Miller, R.C. (1973). Food Extrusion. Food Technology, 27(8): 46–53.

Ranganna, S. (1997). Handbook of Analysis and Quality Control for Fruit and Vegetable Products.

2nd edition, Tata McGraw Hill Publishing Company Ltd., New Delhi, India.

Riaz, M.N. (2000). Extruders in Food Applications. Technomic Publishing Company Inc.,

Lancaster, Pennsylvania, USA.

Rinaldi, V. E. A., Ng, P. K. W., and Bennink, M. R. (2000). Effects of extrusion on dietary fiber

and isoflavone contents of wheat extrudates enriched with wet okara. Journal of Cereal

Chemistry, 77(2): 237-240.

Srivastava, B., Singh, K.P. and Zimik, W. (2009). Effects of Blanching Methods on Drying Kinetics

of Oyster Mushroom. International Journal of Food Engineering, 4.

Stojceska, V., Ainsworth, P., Plunkett, A. and Ibanoglu, S. (2009). The effect of extrusion cooking

using different water feed rates on the quality of ready-to-eat snacks made from food by-

products. Journal of Food Chemistry, 114: 226–23.


-48-

Stojceska, V., Ainsworth, P., Plunkett, A. and Ibanoglu, S. (2010).The advantage of using extrusion

processing for increasing dietary fibre level in gluten-free products. Journal of Food

Chemistry, 121: 156–164.

Subba Rao, M.V.S.S.T., and Muralikrishna, G. (2001) Non-starch polysaccharides and bound

phenolic acids from native and malted Finger millet (Ragi, Eleusine coracana, Indaf - 15).

Food Chemistry 72: 187-192

Zecchi, B., Clavijo,L., Martínez Garreiro, J., Gerla , L. (2011). Modeling and minimizing process

time of combined convective and vacuum drying of mushrooms and parsleyJournal of

Food Engineering, 104: 49–55


Date post:	03-Dec-2014
Category:	Documents
Upload:	atri-bhattacharya
View:	38 times
Download:	5 times

Introduction

Documents