NOVEMBER, 2010 Webmaster...i ONWUZULIKE LOVETH C. REG. NO: PG/PGD/08/48553 PG/M. Sc/09/51723 EFFECT...

i

ONWUZULIKE LOVETH C.

REG. NO: PG/PGD/08/48553

PG/M. Sc/09/51723

EFFECT OF SMOKING AND OVEN-DRYING ON SHELF STABILITY AND SENSORY

PROPERTIES OF ATLANTIC MACKEREL FISH FILLETS

(Scomboromorus scombrus)

FOOD SCIENCE AND TECHNOLOGY

A THESIS SUBMITTED TO THE DEPARTMENT OF FOOD SCIENCE AND

TECHNOLOGY , FACULTY OF AGRICULTURE, UNIVERSITY OF NIGERIA, NSUKKA

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Digitally Signed by Webmaster’s Name

DN : CN = Webmaster’s name O= University of Nigeria, Nsukka

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NOVEMBER, 2010

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EFFECT OF SMOKING AND OVEN-DRYING ON SHELF STABILITY AND SENSORY PROPERTIES OF

ATLANTIC MACKEREL FISH FILLETS


PROJECT REPORT



DEPARTMENT OF FOOD SCIENCE AND TECHNOLOGY

UNIVERSITY OF NIGERIA, NSUKKA

NOVEMBER, 2010

TITLE PAGE

iii

EFFECT OF SMOKING AND OVEN- DRYING ON SHELF

STABILITY AND SENSORY PROPERTIES OF ATLANTIC

MACKEREL FISH FILLETS


PROJECT REPORT SUBMITTED IN PARTIAL

FULFILLMENT FOR THE AWARD OF POST GRADUATE

DIPLOMA IN FOOD SCIENCE AND TECHNOOLOGY

UNIVERSITY OF NIGERIA NSUKKA

BY



DEPARTMENT OF FOOD SCIENCE AND TECHNOLOGY

UNIVERSITY OF NIGERIA, NSUKKA

SUPERVISOR: MR. BHANDARY C.S.

NOVEMBER, 2010

CERTIFICATION PAGE

iv

THIS THESIS HAS BEEN APPROVED FOR THE AWARD OF POST

GRADUATE DIPLOMA IN FOOD SCIENCE AND TECHNOLOGY

BY

-------------------------------- ---------------------------

MR. BHANDARY C.S DATE

PROJECT SUPERVISOR

--------------------------------- ----------------------------

DR. ANI J.C. DATE

HEAD OF DEPARTMENT

DEDICATION

This work is dedicated to God Almighty for his infinite mercy and inspired

knowledge in me and also to my beloved husband Mr. Boniface Onwuzulike for his

v

unfailing love, care, financial assistance, moral support, encouragement, guidance and

advice. You are really a model.

ACKNOWLEDGEMENT

With utmost gratitude, I appreciate the mercies, protection, guidance, favour

and goodness of God to me because this work (programme) wouldn’t have been

vi

possible if not for the illumination of life, strength, good health, provision and

knowledge from Almighty God.

I am immensely grateful for the immeasurable support, encouragement, advice

and good will of my lovely husband, family and sisters. I wish to express my

appreciation to my friends who contributed in one way or the other to the success of

this work.

My sincere gratitude also goes to my project supervisor Mr. Bhandary C.S.

whose tolerance, advice, discussion and assistance is incomparable and had added

immensely to the success of this thesis. My gratitude also extend to all my lecturers

especially Prof. T.M. Okonkwo for his advice and word of encouragement to me, Prof.

A.I Ikeme, Dr. Okafor G.I., Mrs. Ify Nwacha and to all the staff of department of Food

Science and Technology whose lectures, advice and encouragement contributed to the

success of this work.

I am immensely grateful to my Head of Department Dr. Ani J.C for her

assistance, advice and encouragement for making my dream come true.

TABLE OF CONTENT

Title - - - - - - - - - - i

Approval page - - - - - - - - ii

vii

Dedication - - - - - - - - - - iii

Acknowledgement- - - - - - - - - iv

Abstract - - - - - - - - - - v

Table of Content - - -- - - - - - - vi

List of Tables - - - - - - - - - ix

List of Figures - -- -- - - - - - - x

CHAPTER ONE: INTRODUCTION

1.1 Importance of Fish and Fish Products - - - - 1

1.2 Fish in Human Diet - - - - - - - - 1

1.3 Fish in Industry and Commerce - - - - - - 1

1.4 Fish Production in Nigeria - - - - - - - 2

1.5 Importance of Smoke Curing of Fish - - - - - 3

1.6 Merits of Smoking Fish - - - - - - 4

1.7 Smoking and Drying and its effect - - - - - - 4

1.8 Aims and Objectives - - - - - - - 5

CHAPTER TWO: LITERATURE REVIEW

2.1 Fish Handling, Transportation and Distribution in Nigeria - 6

2.2 Methods of Processing and Preservation of Fish - - - 6

2.3 Importance of Smoke Curing - - - - - - 8

2.4 Effect of Smoking on Quality Characteristic of Fish - - - 10

2.5 Types of Smoking - - - - - - - 11

2.6 Effect of Smoking on Chemical Component of Fish - - - 13

2.7 Rancidity Development in Smoked Fish - - - - 14

2.8 Smoking and Drying of Fish - - - - - - 15

2.9 Advantages of Smoking of Fish Fillet- - - - - 15

CHAPTER THREE: MATERIALS AND METHODS

3.1 Sources of Raw Material - - - - - - 16

3.2 Preparation of Fish for smoking - - - - - 16

3.3 Fish Smoking - - - - - - - - 16

3.4 Drying of smoked fish fillets - - - - - - 18

3.5 Determination of physico-chemical changes (properties) in smoked

and dried fish fillets - - - - - - - 18

3.6 Determination of moisture content - - - - - 18

viii

3.7 Determination of water activity (aw) - - - - - 19

3.8 Determination of Crude Protein - - - - - - 19

3.9 Determination of fat content - - - - - - 20

3.10 Determination of Ash content - - - - - 21

3.11 Thiobarbituric acid value determination - - - - 21

3.12 Peroxide value determination - - - - - 22

3.13 Determination of total viable count - - - - - 22

3.14 Mould count Determination - - - - - - 23

3.15 Sensory evaluation - - - - - - - 24

CHAPTER FOUR: RESULT AND DISCUSSION

4.1 Dimensions of the Fresh Fish - - - - - - 25

4.2 Temperature and relative humidity of smoked and dried fish fillets

Storage Environment - - - - - - 25

4.3 Proximate composition of fish - - - - - 25

4.4 Moisture content of smoked and dried fish fillets during storage - - 26

4.5 Effect of storage on the water activities of smoked and dried fish fillets 27

4.6 Effect of storage on the thiobarbituric (TBA) value of the

smoked and dried fish fillets - - - - - 28

4.7 Effect of storage on the peroxide value of smoked and dried fish fillet 29

4.8 Effect of storage on total viable count (TVC) (cfu/g) of smoked and

dried fish fillet - - - - - - - 30

4.9 Effect of storage on mould count (cfu/g) of smoked and dried fish fillets 30

4.10 Sensory characteristics of smoked and dried fish fillet - - 31

CHAPTER FIVE: CONCLUSION AND RECOMMENDATION

5.1 Conclusion - - - - - - - - 34

5.2 Recommendation - - - - - - - 35

References - - - - - - - - 36

APPENDICES

Appendix I: Dimensions of the fresh fish - - - - 40

Appendix II: Dimensions of the dressed fish fillets - - 41

Appendix III: Wet and dry bulb temperature and relative humidity

of different days of smoked and dried fish fillets

during storage - - - - - - 42

ix

Appendix IV: Sample score sheet used by taste panel - - 43

Appendix V: ANNOVA for appearance of smoked and dried fish fillets 44

Appendix VI: ANNOVA for saltiness - - - - 45

Appendix VII: ANNOVA for flavour - - - - 46

Appendix VIII: ANNOVA for colour - - - - - 47

Appendix IX: ANNOVA for taste - - - - - 48

Appendix X: ANNOVA for general acceptability - - - 49

LIST OF TABLES

Table 1: Proximate Composition of fresh fish (raw fish), freshly smoked

fished fillet, and different samples of smoked and oven

x

dried fish fillets - - - - - - 26

Table 2: Effect of storage on the moisture content of different samples

of the smoked and dried fish fillets - - - - - 27

Table 3: Effect of storage on the water activities of smoked and


Table 4: Effect of storage on the TBA value of the smoked and

dried fish fillet - - - - - - - 29

Table 5: Effect of storage on the peroxide value of smoked and

dried fish fillets - - - - - - - 29

Table 6: Effect of storage on total viable count (TVC) (cfu/g) of smoked

and dried fish fillets - - - - - 30

Table 7: Effect on storage on mould counts (cfu/g) of smoked and


Table 8: Changes in the appearance of smoked and dried fish fillets

during storage - - - - - - - 31

Table 9: Changes in the saltiness of smoked and dried fish fillets


Table 10: Changes in the flavour of smoked and dried fish fillets


Table 11: Changes in the colour of smoked and dried fish fillets


Table 12: Changes in the taste of smoked and dried fish fillets


Table 13: Changes in the general acceptability of smoked and dried fish

fillets during storage - - - - - -- 33

LIST OF FIGURES

Figure 1: Flow chart of fish smoking and drying process - - - 17

xi

ABSTRACT

The work was carried out to determine the effectiveness of smoking and oven drying on

the shelf stability and sensory characteristics of Atlantic mackerel fish fillets during

xii

storage. In the study, mackerel fish was eviscerated and cut into fillets, weighed and

measured, cleaned and dipped in 75% saturated brine for 1 minute. It was smoked at a

temperature of 60-70oC for 4hours. Products were then divided into four (4) batches

after smoking and cooling. One batch was kept at room temperature as control while

the remaining 3 batches were oven dried at 70-80oC for 1hour, 2hours and 3hours

respectively. The smoked and dried fish fillets were later stored at room temperature

including the control (sample A) for 21days and were analyzed for physical, chemical,

microbial and sensory qualities. Result indicated that moisture content and water

activity of the products decreased as storage period increased. The thiobartituric acid

(TBA) value and peroxide value increased during storage and decreased with drying

time. It was noticed that the mould count increased with storage period but decreased

with drying time and the same was also applicable to the total viable count. The sensory

evaluation studies showed a significant difference (p<0.05) within samples in respect of

appearance, flavour, tastes, saltiness and colours. The result of the sensory evaluation at

the later storage days gave a general preference for the 3hours oven drying sample.

Based on the result obtained from the treatments a drying period of three (3) hours was

recommended. This was because this treatment (sample D) gave a product with the best

general acceptability and also gave a product of low moisture content, low water

activity and was more shelf stable.

1

CHAPTER ONE

INTRODUCTION

1.1 Importance of fish and fish product

Fish is an aquatic organism with adaptive physical features, which enable it to

live conveniently in water. These physical features are mouth, operculum (gill cover)

fins, eyes, lateral lines, scales, nostrils and barbell, among others.. Fish is a major

source of food for humans, providing a significant portion of the protein (which is

essential for healthy human growth), fats and fat-soluble vitamins intake in the diets of

a large proportion of the people, particularly so in the developing countries.

Fish is also used as a source of valuable medicinal, feeding and technical

products. Fish is a cheap sources of animal protein and fat with little or no religious

rejection. This gives it an advantage over pork, chicken or other meat (Johnson and

Peterson, 1974). That such use can be made of fish is explained by the various

historical and chemical composition of its different parts. The size, chemical

composition and food value of fish depends on their species, age, sex physiological

state, and on the conditions in which they live. Since fish is a highly perishable

commodity, proper processing and storage are very important factors to maintain in

order to extend its shelf life (Merindol, 1967).

1.2 Fish in Human Diet

In the world as a whole, fish represents a major source of animal protein, fat,

mineral and vitamin (Johnson and Peterson, 1974). Marine fish and shell fish are by far

the richest source of iodine in human diet (Ashwood, 1985). The annual fish landings

for 1989 were 99.5 million tones of which 62.2 millions tonnes were caught for human

food with remaining 37.3 million tonnes being reduced to fish meal. In terms of total

world supplies fish contributes about 6% of all proteins and 18.1% of animal proteins.

(Johnson and Peterson, 1974). These figures however, conceal a wide variation in the

importance of fish in the diet as found in many developing countries where it is a major

and sometimes the sole source of animal protein. (Greiger and Borgstrom, 1962).

1.3 Fish in Industry and Commerce

Some of the uses of fish and fish products include the manufacture of

Nitrogenous fertilizers from fish and fish scrabs, the extraction of fish liver oils as one

of the sources of vitamin. A and D, control of mosquito borne disease, a potential tool

2

in medical research and the manufacture of pet food. Fish scales are used in making

artificial pearls. Isinglass, a form of gelatine is prepared from the swim bladder of

certain species, and glue can be made from fish offals, fins from shark fish can be used

for fin soup. Fish head can be used for fish meal. An alternative use for fish skin would

be to produce leather from them. Only shark skin can be used to make attractive leather

but suffer from disadvantage that the shagreen (the shark tooth like scales) must be

removed (Clucas 1982). In Nigeria today, fish ponds have been made by individuals as

a part of business which yields a large amount of money for the country thereby

contributing in the improvement of the economy and provision of employment.

1.4 Fish Production in Nigeria

Nigeria is a maritime state of about 140 million people with a coastline

measuring approximately 853 kilometers. Of the 36 states of the federation, nine are

located on the coast where the waves of the Atlantic Ocean lap against the land. With

this scenario, the natural expectation is that Nigeria should not only be self-sufficient in

fish production but should also be an exporter of aquatic foods.

Nigeria once used to be self sufficient in fish production. At the coastal regions

and riverside dwellings, people used to engage in fishing as a major source of family

income. The discovery of oil in commercial quantity however changed all that. Youths

in the Niger Delta region took to oil-related activities in preference to fishing. Fishing

suffered as part of the general neglect of agriculture in the country (Anthonio and

Akinwumi, 1991).

Even the few artisans left in the trade have only embraced modern methods of

fishing, reluctantly. At a time when commercial fishing is done with trawlers and

motorized boast, some Nigerians still rely on nets and canoes for their trade. The

vacuum created has been filled by foreigners who take advantage of the situation to

plunder our waters illegally and sell their catches back to Nigeria at exorbitant cost.

(Asia, 1997).

The fisheries sub-sector in Nigeria account for about 40% of animal protein in

the diet and it contributed 4.74% of the agricultural share of the nation in 2003

(Matsuda et al., 2004). In 1998, the domestic production of fish was 292,800 million

tones. If there is anyone out there interested in fish farming in Africa, Nigeria is the

best place to set up, such business. According to findings, Nigeria is the largest African

aquaculture producer at 15.489 million tones a year. (Asia, 1997).

3

With annual domestic fish supply of about 400,000 million tonnes, the fisheries

sector account for 2 percent of national GDP of the country. It also contributes

substantial proportion of employment, especially in rural areas (Asia, 1997).

In 1997 alone, for instance, Nigeria’s fish demand stood at 1.27 million metric

tonnes. The domestic fish demand in 1998 was 1.52 million tonnes. Recently, demand

for fish production has doubled as other sources of animal protein have become

expensive due to pressure by the ever-increasing population and high production cost of

the other animal protein sources. (Asia, 1997, Matsuda et al., 2004).

Nigeria has become one of the largest importers of fish in the developing world,

importing some 600,000 metric tonnes annually (Anthonio and Akinwumi, 1991). To

solve the country’s high demand for fish, Nigerians must turn to their under utilized

inland water for improved fish production and Aquaculture. Aquaculture expansion,

moreover, has been a slow process, as private sector fish farmers have faced major

constraints, including lack of seed and quality food (Anthonio and Akinwumi, 1991).

1.5 Importance of Smoke Curing of Fish

Salt has long been used both as the primary preserving ingredient and is also

used with other methods, such as drying and smoking. In recent years, salting as

preservation technique has become less popular because of the development of quick

freezing preservation method of fish. Frozen fish have much the same flavour as fresh

fish while salted fish a distinct flavour derived from the salting process. Salting is a

preliminary treatment in smoked dried fish that is used either to provide a salty flavour

or impart storage stability by decreasing the water activity. Many researchers have

studied conventional salting methods and suggested improvements. Sen and Lahiry

(1964) in their investigation using Indian mackerel studied the effect of sun drying on

the quality of salted and dried product.

The importance of fish curing is that salt slows down spoilage process in fish

which is brought about by autolysis and bacterial decomposition. Some level of salt

absorption by the fish, the bacterial growth and activity are arrested and spoilage is

prevented. The presence of more than 6% salt in solution in the tissue of fish retards

both autolysis and bacterial decomposition (Sen and Lahiry, 1964).

4

1.6 Merits of Smoking Fish

Smoking is relatively cheaper than other preservation methods.

Smoking can be done with little or no machinery.

Smoking is a preservation method and at the same time improves the

organoleptic properties of food (flavour, colour, aroma, softness etc).

Smoking does not require skilled labour.

Effective smoking under good conditions is hardly hazardous to health.

Smoked products are valued and priced among consumers unlike some

other methods such as salting.

Smoking improves the nutritional properties of fish unlike some other

preservative methods.

Demerits of Fish Smoking

In traditional smoking, the smoked products may not be of uniform

quality.

Unlike other preservation and processing methods, smoking alone

cannot extend the shelf life of fish for a long time.

As a result of uncontrolled nature of hot smoking process, traditionally

prepared hot smoked fish may be charred in extreme cases (Hoffman,

1977).

1.7 Smoking and Drying and its Effect

Smoking is a popular processing method and nearly 45% of the fish catch is

consumed in this form. (Schafer, 1986 and Ikeme, 1990). Smoke curing as applied to

fish is a method of preservation effected by a combination of drying and the deposition

of naturally produced chemicals resulting from thermal break down of wood. There are

two main effects of smoking on fish: firstly is the peculiar attractive flavour imparted

and secondly is the better keeping quality of smoked fish when compared with wet fish.

The short period of curing to which the fish is subjected prior to smoking is

mainly responsible for the increased keeping power. Smoking contributes to some

extent to the inhibition of bacterial growth by extraction of moisture and deposition of

antiseptics such as phenols. The efficient smoking of fish results in the finished product

having a dry and glossy appearance while possessing a most attractive odour and

flavour. Drying also reduces the moisture content of smoke thereby extending the shelf

5

stability of the fish. Fish smoking and drying are widely accepted both as a food as well

as preservative method. (Merindol, 1967).

1.8 Aims and Objectives

1. To determine the effect of smoking and oven-drying on the

stability of fish fillets during storage.

2. To assess the effect of smoking and oven-drying on the

organoleptic quality of fish fillets during storage.

6

CHAPTER TWO

LITERATURE REVIEW

2.1 Fish Handling, Transportation and Distribution in Nigeria

In 1840s, the rapid growth of logistical infrastructure (railways and steam ships)

began and this enabled the transportation of perishable foods. For the first time in

human history, it was possible to move large quantities of fresh fish from one place to

another. This marked the beginning of sea fishing industrialization (Bhalla, 1985).

Water, road and rail transportation are all used to carry fish over long distances from

the harvesting points to market centres and also to distribution and consumption areas.

Handling, transportation and distribution of fresh fish in interior areas are

difficult and expensive because of:

Lack of appropriate facilities in the sense that there are little or no

facilities in such an area and this will lead to difficulties in the fresh fish

transportation and distribution.

The topography of the area can cause difficulties also due to rivers, valleys and

non motorable roads. In some cases the areas may be swampy and inaccessible thereby

restricting the movement of vehicles. In the interior areas, there is no power supply or

its alternatives which contribute to difficulties in the transportation and distribution of

fish. Ignorance by the people in the interior areas make this transportation and

distribution very difficult and expensive because it may lead to poor management,

preservation and processing of fish. Less dense areas can also cause difficulties because

the population in such an area may not be enough to consume all the catch at once. So

to avoid these difficulties, an alternative measure has to be taken which is processing

and preservation of fresh fish.

2.2 Methods of Processing and Preservation of Fish

Fish is most susceptible to decomposition, development of rancidity and

microbial spoilage. Therefore there is a great need to process and preserve the fish in

order to extend its shelf life (Schafer, 1990). Some of the processing and preservation

techniques are salting, drying, smoking, canning, freezing, pickling and irradiation

among others.

7

SALTING

Salting of fish is a traditional processing method. Our earliest records of food

preservation practices include using salt for preserving fish. Salt has long been used

both as primary preserving ingredient and in combination with other methods, such as

drying and smoking. Salting is usually done by one of the two methods: Brine salting

and dry salting.

DRYING: This is the removal of water from fish by evaporation. Removal of

water can also be done by some other methods such as the action of salt and application

of pressure. Water removal is very important since the activities of all living organisms

depend on it. Drying has existed as a traditional method of preserving fish. The action

of the sun or wind is used to effect evaporation of water from fish. Nowadays, the

controlled artificial dehydration of fish has been developed in some industrialized

countries so that fish drying can be carried out regardless of weather conditions.

SMOKING: This is a processing and preservation method that combines the

effect of drying, cooking and preservative value of the smoke. In smoking method, the

fish is split, eviscerated and put in salt solution. After which the fish is hung or kept in

racks in a kiln and exposed to smoke from burning wood and a desirable color, taste

and flavour is achieved by the deposition of phenols and other organic component from

the burning wood.

CANNING: Canning of fish in Nigeria is in its infant stage and the local

production of canned fish is still awaited (Ikeme and Bhandary, 1986). Fish may be

processed and preserved by canning in brine oil, tomato sauce etc, depending on the

consumers preference. Maintaining excellent sanitary condition and handling raw

material with utmost care will greatly help in obtaining a good canned product.

FREEZING: This is the most convenient and most highly recommended

method of fish preservation. Good quality fresh product requires the reduction of the

temperature of fish to 30oC and keep in deep freezer or cold room.

PICKLING: This is an easy method of preserving fish. In pickling of fish, a

layer of any salt is spread over the bottom of the tank upon which the first layer of fish

is laid. However, there is no need to stack fish higher in the centre as drainage is not

required. The layers of salt and fish are stacked up, care being taken to ensure that no

fish is overlapped without a salt layer between them since this could cause the fish to

stick together. As the pile is built up, the salt layer should become thicker. The top

layer of fish must be placed on this top layer so that weights can be stored in the

8

refrigerator at not higher than 40oF and for best flavour it must be used within four to

six weeks. (Schafer, 1990).

In Nigeria, the greater portion of fish caught and preserved by smoking and sun

drying (Johnson and Peterson, 1974). The simplest and most widely practiced method

is smoking using traditional methods of fish smoking. In the riverrine areas, fishing

towns and villages are scattered and far away from consuming centres. Most of the fish

caught are smoked by traditional method using drum type smoking kiln in open space

under unhygienic conditions (Bhandary et al., 1988). Smoking has the advantages of

increasing the shelf life of fish since water that create favourable condition for mould or

bacteria growth has been drastically reduced. Also smoking enhances the flavour,

colour and odour/aroma of the fish. Intramuscular phospholipids have been shown to be

the most rapidly oxidized lipid component in smoked fish or meat (Igene and Pearson,

1979). Awareness of these constraints and limitations prompted many research

organizations to develop improved method of smoking.

One of the improved type of kiln was developed at the Nigeria Institute of

Oceanography and Marine Research (NIOMR). In this kiln, the central dome acts as the

heat exchanger and to maintain the uniform temperature inside smoking kiln. The

smoke produced enters the heat exchanger and then enters the smoking kiln through the

tubes because of this arrangement, there is uniform distribution of smoke inside the

smoking kiln and temperature is controlled by adjusting the addition of fire wood and

wet saw dust inside the fire place. The smoke circulates uniformly inside the smoking

chamber and then escapes at the top. A smoke kiln may be linked to a large square

rectangular chimney, opened at the bottom as in the case of the fire place.

The mechanical kiln is more easily controlled and gives a more uniform and

more hygienic product with less labour. In smoking using mechanical kiln method,

factors such as humidity, temperature and speed of smoke are under the control of

operator and the efficiency of the cure is unaffected by the weather condition. An

example of this type of kiln is Jorry mechanical kiln and it is more suitable to factory

operations (Matsuda et al., 2004).

2.3 Importance of Smoke Curing

Smoke curing is a method of improving the preservation and taste of food such

as meat and fish. It also helps to improve the appearance of the product. Smoke curing

of fish is a traditional method aimed at preserving fish by exposure to heat and smoke

9

(Ikeme and Gugnani, 1988). Preserving fish and meat with smoke curing has taken

place for thousands of years as freezers, refrigerators and canning are all recent

technologies. In Nigeria, greater portion of fish caught are preserved by smoking and

sun drying (Ikeme,1986).

Smoke dried products are considered a delicacy in many African countries and a

good proportion of fish is consumed smoked (Bhandary et al., 1988). “It is said that

after you have tested smoked fish, you will be well and truly hooked” (Laurie and Mc-

allydon, 2006). The original basis for fish processing by smoking is to add flavour.

During smoking, the component of wood smoke deposited on the fish not only imparts

good flavour and colour, but also increases fish stability due to its bactericidal and

antioxidant properties. Phenolic compounds, acids and carbonyl present in wood smoke

are believed to be responsible for these favourable changes (Porter et al., 1965).

Smoked fish is an important component of staple diet in many tropical countries.

However, smoked fish products are shelf stable only if they are sufficiently dehydrated,

or if the salt content is sufficient to lower water activity to a level that would not

support microbiological activities.

In Nigeria, the advantages of traditional methods of smoking described by

Tabor (1985) are affected by poor smoking flavour, poor hygiene, poor flavour, low

shelf life and the lack of control of smoking. According to Laurie and Mc-allydon

(2006), smoked fish despite all odds, is still highly relished in Nigerian traditional diets

and it is unlikely that an acceptable substitute will be found in the near future.

Improved methods of smoking, such as the use of smoking kilns developed by the

Nigerian Institute of Oceanography and Marine Research (NIOMR), combine

appreciable reduction in water content, hygienic process and makes uniform

distribution of smoke on fish flesh and better smoking flavour. Any fish can be smoked,

however, fatter fish will absorb more smoke flavour, so fish like, mackerel, salmon and

trout are perfect for smoking (Laurie and Mc-allydon, 2006).

According to Daun (1975) smoked products are known to posses an increased

resistance to oxidative changes in fatty foods such as fish. The phenolic substances

found in smoke are believed to be responsible for such effects on foods. Tabor (1985)

recorded that smoking and drying treatment applied to fish account for 45% of the total

preservation methods available to rural fisherman. Bhalla (1985) emphasized the need

for quality raw materials in smoking operation and warned that smoking should never

10

be used as a method for disguising the flavour of stale fish. It is important to note that

smoking alone cannot preserve the fish effectively (Ikeme, 1990).

2.4 Effect of Smoking on Quality Characteristic of Fish

Smoking effect on quality to a large extent depends on the freshness of fish

used. This is because it takes first class fish to make a first class product. Also like the

old saying “Garbage in, garbage out”, a good product cannot be made from stale fish.

Some folks believe that smoking can cover up mouldy stale fish off flavour. This is

false because any unpleasant odours or flavours will be readily apparent. Smoked fish

whether prepared in the open air, in the chimney, over fire or in a well-controlled air

tunnel can never recover the properties of the fresh fish from which it was made, no

matter how efficient the process or how good the storage. Smoked fish should be

regarded as a completely different product with its own particular flavour or texture

(Schafer, 1990).

Given that the fresh fish are of good quality, smoking affect quality

characteristics such as weight, texture, colour, flavour and general acceptability.

Weight loss during smoking depends upon the type of fish, temperature and the time of

smoking. Alteration in the smoke production can lead to significant change in the

composition of the final product and hence alter the flavour. The texture of cold

smoked fish has been described as soft and tender while that of hot smoked is tough

and dry by virtue of being exposed too much to higher temperature (George and

Maynard, 1973). The main reasons: for textural change are water loss, fat diffusion and

denaturation of structural and connective tissue, protein and enzyme activity brought

about by proteolysis (George and Maynard, 1973). Smoking also affect the natural

condition of the fish such as fat for example, spring herring and mackerel are low in fat

and make a poor quality product after smoking. Haddock that have recently spawned

cannot be expected to turn out well. Atlantic salmon with a fat content much in excess

of 14% becomes too oily and can oxidize rapidly after smoking (Bhalla, 1985).

Choice of wood for smoke generation is very necessary in order to impart

desirable colour, flavour and odour to the smoked product (Clucas, 1982). Smoking

drains off excess liquid in a fish product and allows the formation of an attractive gloss

colour. The gloss is actually the drying of a water-soluble protein and such a pellicle is

the mark of a high quality smoked fish (Bhalla, 1985). This is because colour of

smoked fish affects the consumer’s appeal. The odour and colour formation is due to

11

browning involving carbonyl amine reaction; phenolic compounds do not participate

directly in colour formation but acidic compounds influence colour formation by

surface protein hydrolysis by depositing brown pigments on the surface tissues thereby

inhibiting the penetration of carboxyl and other smoke compounds. This is because,

most phenols are absorbed by fat rather than by moist surfaces due to their

predominately lipophilic character and they (phenols) are not reactive towards amino

groups. However, since fish has bacterial population, smoking also affect the fish

quality by killing or inactivating the microorganism thereby enhancing the quality and

the shelf life. (Agu and Bhandary, 2005)

2.5 Types of Smoking

Basically, we have 2 kinds of smoking, cold smoking and hot smoking (Agu

and Bhandary, 2005).

Cold Smoking

In cold smoking, the temperature at no time rises to a level where the fish is

cooked (the protein is denatured). The smoking operation is carried out at a maximum

temperature of approximately 30 – 40oC and is only really possible in temperate

climates (Clucas, 1982). Fish which are cold smoked are hung after preparation (which

usually includes splitting) at a set distance from the smoked house (Bhalla, 1985).

Temperature constraints tend to limit cold smoking in its strictest sense, in cool

climates. The storage life of cold smoked fish depends on the length of time the fish is

smoked, the loss of moisture and whether salt has been used. The temperature at no

time should rise to a level where the fish is cooked (that is to a temperature where the

fish protein is denatured). Cold smoking requires rigorous quality control, strict

hygiene practices and the product must be kept in chilled or frozen storage. Bhalla

(1985) warned that cold smoking as a means of preservation cannot be generally

recommended for use in developing countries which lack the required cold storage and

distribution facilities.

Hot Smoking

The temperature used for hot smoking can vary from 65oC to 100

oC. The fish is

partially or wholly cooked within a short time of 2 – 41/2 hours (Bhalla, 1985, Agu and

Bhandary, 2005). In the initial stages of hot smoking, it is important that the fish is not

subjected to excessive high temperatures as this will result in the flesh being cooked

and breaking up prior to the formation of a surface skin, which will hold it together.

12

According to Ikeme (1990) if hot smoking is continued over an extended period, drying

will take place, thus resulting in smoke dried products with extended life. It is essential

that the fish be left to cool well after smoking. At refrigerated temperature of 3 to 8oC

smoked fish can be stored up to 7 days without deterioration.

Smoking Kilns

Smoke-curing of fish is usually carried out in smoking ovens or kilns (Essuman,

1985). Generally, there are two types of smoking kiln.

(a) Traditional smoking kilns

(b) Mechanical kilns

Improved Traditional Smoking Kiln

Most traditional kilns used for smoke drying are very simple in design and

construction (Bhalla 1985). They range from the simplest type; which is an open fire

above which the fish are placed or racks above a fire. According to Bhalla (1985), the

main disadvantage from this type of smoking kiln is the lack of control over the

temperature, insufficient use of fuel and how to put off material. Examples of improved

traditional kilns are oil Drum kiln. Altons type kiln, Ivory Coast type kiln.

In Nigeria, Nigerian Institute of Oceanography and Marine Research (NIOMR)

designed an improved, traditional kiln which is popular for fish smoking. Traditional

smoking entails placing fish on wire gauze or a wood fire kiln made of steel drum. In

the study by Ikeme and Uwaegbute (1988) samples were smoked at 75 – 88oC for 4

hours. Hardwood was used for smoking.

Mechanical Kiln

In mechanical kilns, forced convection is responsible for smoking operations. In

most designs it is possible to regulate the relative humidity, temperature, smoke density

and air velocity so as to guarantee product uniformity, a prerequisite for the

sophisticated smoked fish market.

Mechanical smoking kilns are used extensively in Europe and North America

where production of products such as kippered herring and buckling requires a high

degree of control. According to Bhalla (1985) the main advantage of mechanical

smoking is the uniform quality product. However, the equipment is generally very

13

expensive and the extra expense may not be worth considering for the most third world

situation.

2.6 Effect of Smoking on Chemical Components of Fish

It is generally accepted that smoking is associated with chemical changes of

some protein functional groups (Daun, 1975).It also has some effects on the nutritional

value of the fish. Processing by smoking is applied to produce a product of desirable

flavour, colour and quality (Agu and Bhandary, 2005). However, losses of nutritive

value are reduced by the bactericidal properties of the phenolic compounds present in

smoke (Daun, 1975). Actually, the bactericidal action found in smoking is due to the

combined effect of heating, drying and the chemical components such as formaldehyde,

acetic acid and phenols. These components have been found to prevent spore formation

and growth of many bacteria and fungi and to inhibit viral activities (Daun, 1973). High

boiling phenols present in the smoke also show high bactericidal properties (Draught,

1963).

Fish is composed of protein (amino acid) moisture, lipid, vitamins and minerals.

These nutrients are affected during smoking. The protein and amino acid; depending on

the intensity of heat generated during smoking is denatured and this leads to alteration

in the physical and chemical properties of protein (Ihekoronye and Ngoddy, 1985).

Smoking also decreases the more soluble proteins like myofibrillar and sarcoplasmic

proteins and increases the amount of insoluble proteins (Ashwood, 1985). Severe

heating reduces lysine and other amino acids are essentially (directly) related to the

time and temperature of processing (Laurie, and Mc-allydon, 2006). Though other

workers have recorded smaller losses in the range of 6 – 33% (Hoffman et al,, 1977).

There are also losses in serine, threonine and sulphur containing amino acids during

smoking. The phenols and polyphenols in the smoke tend to react with sulphydryl

groups, where as the smoke carbonyl groups react with the amino groups (Draught,

1963).

The moisture and oil are inversely proportional in fish. Water is one of the

major components of fish and plays a vital role in the changes taking place during

processing and storage of fish. The water content of food products has wide range of 3

– 93%. Fish usually contain about 55 – 83% moisture, which participate in its body

structure (Johnson and Peterson, 1974) but the average moisture in fish is about 70%.

14

Fat content of fish varies from species to species depending on feeding

condition, maturity, location of catch and part of the fish used for the analysis. It has

been shown that fish is an important source of mineral (iodine). This iodine was shown

to be destroyed by salting and smoking in a large extent. The different processes of

smoking therefore, affect considerably the chemical composition of fish.

2.7 Rancidity Development in Smoked Fish

Rancidity can be referred to off-flavour and colour which results from the

chemical deterioration of fats or undesirable chemical changes that occur in fatty foods.

The mechanism of the lipid oxidation proceeds through free radical chain reaction. If a

free radical produced, it reacts with oxygen to produce peroxide, lipid peroxide radicals

(Roo) or hydrogen peroxide (RooH) though the peroxides do not give off flavour and

colour and they are unstable. Peroxides are broken down to yield more free radicals that

initiate a chain reaction and these radicals are responsible for the off flavour produced

in smoked fish (Ihekoronye and Ngoddy, 1985, Fellows, 2009). Rancidity normally

develops in many fatty fishes during storage. This is because of the highly unsaturated

fatty acids which are susceptible to oxidation and some acids are said to have an

unpleasant flavour and odour (Fellows, 2009).

As described above, the fish product contains phospholipids and

polyunsaturated fatty acids. The breakdown of these components leads to the

production of unpleasant flavour that is rancidity development. The oxidative quality

changes in smoked fatty foods include the development of off flavour from the auto-

oxidation of the unsaturated fatty acids, which also results in off odours and

discolouration of the smoked fish.

This problem of rancidity can be checked by the use of the antioxidants.

Antioxidants such as butylated hydroxyl Anisole (BHA), butylated hydroxyl Toluene

(BHT) and propyl Gallate (PG) are commonly used to stabilize food (fish) which by

their chemical composition would readily under go some significant losses in quality

(as a result of rancidity) in the presence of atmospheric oxygen (Fellows, 2009).

15

2.8 Smoking and Drying of Fish

Smoking is a popular processing method and nearly 45% of the fish catch is

consumed in this form (Schafer, 1986 and Ikeme, 1990). Smoke curing as applied to

fish is a method of preservation effected by a combination of drying and the deposition

of naturally produced chemicals resulting from thermal breakdown of wood. There are

two main effects of smoking on fish: Firstly, is the peculiar attractive flavour imparted

and secondly is the better keeping quality of smoked fish when compared with wet fish.

The short period of curing to which the fish is subjected prior to smoking contribute to

its increased keeping quality . Smoking contributes to some extent to the inhibition of

bacterial growth by extraction of moisture and deposition of antiseptic such as phenols.

Sun drying also reduces the moisture content of smoke thereby extends the shelf

stability of the fish. Fish smoking and drying are widely accepted both as a food

delicacy as well as a preservative method.

2.9 Advantages of Smoking of Fish Fillet

These are some of the advantages of smoking of fish fillets.

Smoking of fish fillets helps to improve the taste and colour of the fish

fillet and also helps to enhance the flavour when used in sauces.

It helps to reduce the number of bacteria and increase the anti-oxidation

effects.

They are (smoked fish fillets) safe and healthy to consume.

It helps to prolong the shelf life of the fish.

The phenols in wood smoke have an anti-bacteria properties which

forms a protective layer on the surface, protecting the product from

bacteria attack.

Smoked fish fillet is a great way to get omega 3 fatty acids.

16

CHAPTER THREE

MATERIALS AND METHODS

3.1 Source of Raw Material

The principal raw material used in this research work is oily Atlantic Mackerel

fish (Scomboromrus scombrus). The fish was purchased from a local cold store at main

market in Nsukka Town, Enugu State. The common salt was purchased from the same

market. The fire wood and saw dust used for the generation of heat and smoke were

sourced from timber shed in Nsukka, Enugu State.

The smoking kiln used for this research work is the one at the Department of

Food Science and Technology, University of Nigeria Nsukka, which was built based on

design provided by Talabi and Igbinosun (1977) at the Nigeria Institute for

Oceanography and Marine Research (NIOMR) Lagos.

3.2 Preparation of Fish for Smoking

Each of the 40 uniform sized raw frozen mackerel fish was allowed to thaw at

room temperature. The thawed fish was measured in length and weight and was cut into

fillets, (80 in number). Clean water was used to wash the prepared fillets. Brining was

carried out by dipping the fish fillet into 75% saturated brine which was made by

dissolving 27g of salt (NaCl) in 100ml of water for ½ minute. The fish fillets were

rinsed in fresh water and were spread in trays and were taken for smoking.

3.3 Fish Smoking

The firing section of the kiln was filled with hardwood together with saw-dust

and wood shavings to produce smoke. Fishes were introduced into the smoke house

(preheated for 30 minutes). The temperature of the smoking chamber was maintained at

60 – 70oC by adjusting the firewood and saw dust burning in the hearth The fish fillets

were smoked for 3 – 4 hours. The smoked fish fillet were cooled overnight.

17

Fig. 1: Flow chart of fish smoking and drying process

Frozen fish

Thawing

Evisceration and filleting (dressing of fish)

Cleaning

Brining (75% saturated brine solution)

Rinsing

Arranging on trays

Smoking (60 – 70oC for 4 hours)

Cooling

Drying in oven (60 – 70oC

Storage or packaging

0hr

1hr 3hrs

2hrs

Cooling

18

3.4 Drying of Smoked Fish Fillets

The cooled smoked fish fillets were dried in a heating oven for different length

of time to reduce the moisture content and make it dry. The oven temperature was

maintained at 60 – 70oC. The ranges for drying were as follows.

The cooled smoked fish fillets were grouped into 4 batches.

The first batch was the control 0h drying

The 2nd

batch was dried for 1 h

The 3rd


The 4th


The four batches of samples were kept in trays at room temperature for

observation and analysis for 4 weeks.

3.5 Determination of Physico-Chemical Changes (Properties) in Smoked and

Dried Fish Fillets

The temperature and relative humidity of the storage environment of the

smoked dried fish fillet samples were checked daily during the period of storage

(4weeks). The dry and wet bulb temperatures were noted and recorded. The relative

humidity values were obtained from psychometric chart. For the determination of the

dry and wet bulb temperatures, two thermometers were used. One of them was hanged

up in the experimental laboratory, and the readings were recorded as the dry bulb

temperature. The wet bulb readings were obtained by reading of the second

thermometer in which the thermometer bulb was covered with cotton wool and the

lower end of the cotton wool dipped in water. These values were used to calculate the

relative humidity from a psychometric chart.

3.6 Determination of Moisture Content

The moisture content of the fish samples was carried out using the hot oven

method (Pearson 1981). Twog of finely ground fish sample was weighed out with a

chemical balance into a pre dried silica dish and spread over the bottom of the dish to

cover greatest surface area. The dish and the contents were put in an oven maintained at

1000

C and dried for 24hrs. The oven had a mechanical internal fan for even

distribution of heat. The dish and sample were cooled in desiccators and weighed. Then

returned to the oven and dried for further 1hr. Removed, Cooled and weighed until a

19

constant weight was reached. The difference in weight (weight loss) gave the weight of

moisture in the sample.

The percentage moisture can be calculated using the formula.

% Moisture = Loss in weight x 100

Original weight 1

3.7 Determination of Water Activity (aw)

Water activity (aw) of smoked fish fillet was checked once in 2 days as

described by Lupin, (1986). It was determined using the water activity meter (Model

5083) made in Germany. About 50g of well-grounded fish fillet sample was placed in

water activity meter, which was standardized with super saturated barium chloride and

filter paper at 25oC for 3 hours. The sample (covering about ¾ quarter of the bowl of

meter) was allowed to stay for 3 hours in the meter. After the end of the 3 hours, the

value and temperature at which this value was obtained was noted, this was observed

for subsequent days during storage (Egar et al., 1992).

3.8 Determination of Crude Protein

Protein content was determined according to AOAC (1995) procedure using

Kjeldahl method. The total nitrogen of the feeding stuff was converted into ammonia

by digesting with concentrated sulphuric acid. The ammonia was fixed as ammonium

sulphate by the excess of acid. The fixed ammonia was determined by liberating it by

addition of excess of sodium hydroxide and distilling it into excess of saturated boric

acid solution. By titration with standard acid, the percentage of protein was calculated.

The digestion, however was aided by the addition of sodium sulphate which raises the

boiling point of sulphuric acid, copper sulphate and selenium which acts as a catalyst.

METHOD

DIGESTION: About 2g of the sample was weighed into a 100ml flask. The

following chemicals were added into the flask.

5g anhydrous sodium sulphate

1g hydrated cupric sulphate

A pinch of selenium powder

5ml of conc H2SO4

20

The flask was placed on an electric coil heater in a fume chamber, the mixture

was gently boiled at first until blacking occurs, heat was then increased as solution

clears. Heating was continued for at least one hour after solution has cleared. If black

specks persist in the neck of flask, it was an indication of incomplete digestion. The

flask will be allowed to cool, the neck was rinsed down with distilled water, and the

content will be heated for a further period until all specks disappeared. After heating,

the content was transferred with several washings into a 250ml volumetric flask. The

flask was shaken thoroughly and allowed to cool.

DISTILLATION: Steam was passed through the Markham distillation

apparatus for about 10 minutes. 10ml of boric acid was placed in a 125ml conical flask.

The conical flask was placed under the condenser such that the condenser tip was under

the liquid. 5ml of diluted digest was placed in the distillation apparatus and was rinsed

down with distilled water. The cup was closed with the rod and 10ml of 60% NaOH

was put in. This was let in carefully, leaving behind a little to prevent ammonia

escaping. Steam was then let through for about 5 minutes (until the amount of liquid in

the conical flask was about twice what it was at the beginning of distillation). The boric

acid was titrated with 0.01m HCl to the end point. The titre, which was the number of

ml of 0.01m HCl that changes the indicator from green to pinkish colour was noted.

The percentage crude protein was then be calculated as

% crude protein = 0.0001401 x T x 250 x 6.25 x 100

w x s

Where T = Titre value

0.0001401 = Volume of HCl (gN)

250 = Volume of the flask (ml)

W = Weight of the sample

S = Volume of the digest used (ml)

3.9 Determination of Fat Content

Fat content of the fish sample was determined by extracting with non-polar

solvent (petroleum ether with boiling point of 40 – 60oC) in continuous extraction using

soxhlet extractor apparatus.

Two g of a finely ground fish sample was weighed with a filter paper and

poured into labelled cellulose thimble. The tap of the thimble was closed with a piece

of absorbent cotton wool to ensure even distribution of the solvent during extraction.

21

The thimble was then placed into the butt in the soxhlet apparatus. 250ml dried boiling

flask was filled with petroleum ether to about three quarter of the volume of the flask.

The apparatus was set up and allowed for a reflux. The extraction was carried

out for about six hours. After 6 hours, the unit was dismantled, the thimble was

removed and the petroleum ether recovered. The oil was then oven-dried at 100oC and

finally cooled in desiccators and weight taken.

The percentage oil in the sample was determined as shown below.

% fat = Weight of oil extracted x 100

Weight of sample 1

3.10 Determination of Ash Content

The total ash, which is the inorganic residue that remains after the organic

matter has been burnt, was determined using the AOAC (1995) method. The silica

crucible used for the analysis was first oven dried to drive away moisture, cooled and

then weighed.

Two g of ground fish was weighed into the crucible and was pre ashed by

heating in an open heater. After pre-ashing, the crucible was put in furnace at a

temperature of 500oC and ashed for 3 hours. After ashing, the crucible was put in

furnace at a temperature of 500oC and ashed for 3 hours. After ashing, the crucible was

removed from the furnace, cooled in the desiccator and was weighed.

The percentage total ash content of the sample was then be calculated as

follows.

% Ash = Weight of ash x 100

Weight of sample 1

3.11 Thiobarbituric Acid Value Determination

This was determined using Pearson’s method (1981). Five g of fish sample with

25ml of distilled water were macerated for 2 minutes and were washed into distillation

flask with 23.75ml water. 2.5ml of 4M hydrochloric acid was added to bring the pH to

1.5. The flask was heated by means of an electric mantle so that 50ml distillate was

collected in 10 minutes from the time boiling commenced. 5ml of distillate was

pipetted into a glass tube, 5ml TBA reagent (0.2883g 100ml of 90% glacial acetic acid)

was added, shaken and heated in boiling water for 35 minutes, a blank was prepared

22

using 5ml of distilled water with 5ml reagent. Then the tubes were cooled; in water for

10 minutes and the absorbance (D) was measured against the blank at 538nm using

1cm cells.

TBA value (As mg malonaldehyde per 10g sample)

= 7.81

Where D = Absorbance

3.12 Peroxide Value Determination

The peroxide value of the fish samples were determined at 1st, 7

th, 14

th and 21

st

days of storage using Pearson’s method (1981).

One g of oil extracted through soxhlet extraction method was added into a clean

dry boiling tube and 1g powdered potassium iodide and 20ml of solvent mixture of

ratio 2:1 glacial acetic acid and chloroform were added. The tube was allowed to boil in

a water bath for 60 seconds. The liquid was immediately poured into a flask containing

20ml of 5% potassium iodide solution followed by the additional 10mls of distilled

water. A starch solution was added as an indicator and 0.002N(M) sodium thiosulphate

solution was used for the titration. A blank was formed at the same time. The peroxide

value is often reported as the number of ml 0.002N(M) sodium thiosulphate per g of

sample

Peroxide value = T x M x 100

W

Where

T = titre value

M = Molarity of Na2S2O3

W = Weight of the sample used

The result is expressed as milliequivalent per kg.

3.13 Determination of Total Viable Count

The total viable count of each sample was determined by pour plate method

using nutrient agar as the culture medium by (Harrigan and Mccance, 1976). The

method involved grinding the fish sample in a mortar and weighing out 1g into

sterilized test tube. 9ml of 11/4 strength Ringer’s solution was poured into it and was

mixed thoroughly by shaking. Then 1ml of the sample solution was transferred to the

test tube and shaken. 1ml of the solution from test tube No. 1 was pipetted into No. 2

23

test tube containing 9ml of the Ringer’s solution; 1ml of the solution was transferred to

the 3rd

test tube and the serial dilution continued to the last test tube. There after, 0.1ml

was transferred from each test tube into corresponding plate and 15ml of sterile nutrient

agar medium poured and mixed thoroughly by rocking the plates. The plates were

incubated upside down at 37oC for 48 hours after which colonies formed were counted

and expressed as colony forming units per gram. This was done on the 1st, 7

th, 14

th, 21

st

days of storage. The morphological characters on the agar plate were used for tentative

identification where possible.

3.14 Mould Count Determination

The mould count for the fish was done according to the method of Harigan and

Mccance (1976). The moulds were cultured on potato dextrose agar (PDA) medium at

1st, 7

th, 14

th and 21

st days of storage. Here, 65g of potato dextrose agar was weighed out

and dissolved in 1 litre of distilled water in a clean 250ml flat bottom flask and then

sterilized in the autoclave at 15 psi for 20 min at 121oC. It was then allowed to cool a

little bit in a desiccator. It was then poured into sterile Petri dishes and allowed to cool

and solidify at room temperature. For the serial dilution 11/4 strength Ringers tablet was

dissolved in 500ml of distilled water in a 500ml flask, covered with cotton wool and

aluminum foil and sterilized in an autoclave along with the PDA at 121oC for 15 mins.

Four serial dilutions were used for the test. About 9ml of diluents were transferred to

each of the five sterile test tubes with the diluent bottles closed with cotton wool and

aluminum foil. About 2g of the fish sample was transferred to the test tube No. 1and

shaken. One ml of the solution from test tube No. 1 was transferred to No. 2 test tube;

1ml solution was transferred to the third test tube and serial dilution continued to the

last test tube. Then 1ml was taken from each test tube and poured in petridishes with

small quantity of PDA and shaken very well to cover the bottom. The plated dishes

were incubated upside down for 48 hours at 30oC. The mould colonies on each plate

were enumerated and calculated as colony forming units (CFU) per g of sample (f u/g =

No of colonies x Dilution factor.

The moulds on the PDA were identified by their morphological features.

24

3.15 Sensory Evaluation

The sensory evaluation of the various fish fillet samples using a 7-point

hedonic scale (Iwe, 2002) were carried out at 1st, 7

th, 14

th and 21

st days of storage using

a semi trained panel composed of 20 students of University of Nigeria, Nsukka. The

quality attributes evaluated include, appearance, juiciness, saltiness, taste, flavour,

colour and general acceptability. For evaluation, products were first rinsed with water

for 1 minute, covered with aluminum, reheated in the oven at 80oC for 15 minute and

were allowed to coal at room temperature before presentation to panelists. The panel

scores were analyzed using Duncan’s multiple range test to check for samples that

differ significantly from each other. From the score sheet used, I represents (=)

extremely bad, 2 = very bad, 3 = moderately bad, 4 = neither good nor bad, 5 =

moderately good , 6 = very good and 7 = extremely good.

25

CHAPTER FOUR

RESULT AND DISCUSSION

4.1 Dimensions of the Fresh Fish

The average length of the representative sample was 30.9cm with a range of 29 – 33cm

while the average weight was 320g with a range of 200 – 500g as shown in Appendix I.

The dimensions of the dressed fish fillets were taken as follows

The average yield length of the dressed fish fillet was 20.4cm with a range of

17– 23cm while the average yield weight of fish fillet was 87.95g with a range of 60 –

100g as shown in Appendix II.

4.2 Temperature and Relative Humidity of Smoked and Dried Fish Fillets

Storage Environment

The wet and dry bulb temperature of the storage environment were observed

and recorded during the period of 21 days of storage. The relative humidity of the

storage environment was then determined using the psychometric chart.

The average wet bulb temperature of the storage environment was 29.619oC

with a range of 26 – 36oC. The average dry bulb temperature of the storage

environment was 34.667oC with a range of 28-39

oC. Then the percentage relative

humidity was 66.714% with a range of 41 – 93% as shown in Appendix III.

4.3 Proximate Composition of Fish

The percentage (%) proximate composition of fresh mackerel fish as shown in

Table 1 agrees reasonably well with the data presented by Hardy and Keay (1972).

From the Table, there was a marked increase in the crude protein content, crude

fat and ash content while there was a decrease in the moisture content after smoking

and oven- drying as compared to the freshly smoked fish fillet and the fresh fish

sample. This proves that the process of smoking which also entails drying decreases the

moisture while concentrating other food constituents. Similar values were reported by

Ikeme and Uwaegbute (1988) and Lawal et al., (1985) for fresh (frozen) and smoked

mackerel.

The table also showed that protein content, fat and Ash content increased with

drying time. The smoking and drying process had a drying effect on the fish samples,

hence the lower moisture content of smoked and dried fish and corresponding increase

in the protein, fat and ash content relative to smoked and fresh fish. The value

26

obtained also agrees well with the earlier works of Bhuiyam et al. (1986) who observed

that nutritive value of smoked fish was improved as a result of smoking process.

Proximate composition of fresh fish (raw fish), freshly smoked fish fillet,

smoked and oven dried fish fillet samples are reported in table 1

Table 1: Proximate composition of fresh fish (raw fish), freshly smoked fish fillet,

and different samples of smoked and oven dried fish fillets

SAMPLE MOISTURE

(%)

CRUDE FAT

(%)

CRUDE

PROTEIN (%)

ASH (%)

Fresh Fish 63.45 ± 0.030 10.85 ± 0.002 19.47 ± 0.003 1.27 ± 0.002

Smoked Fish fillets 52.56 ± 0.01 12. 71 ± 0.004 20.38 ± 0.05 4.45 ± 0.002

SAMPLE A 48.74 ± 0.003 13.60 ± 0.003 13.59 ± 0.006 4.21 ± 0.005

SAMPLE B 46.14 ± 0.002 15.41 ± 0.005 14.48 ± 0.002 4.45 ± 0.002

SAMPLE C 44.93 ± 0.004 16.01 ± 0.001 14.79 ± 0.003 5.56 ± 0.006

SAMPLE D 43.43 ± 0.002 17.41 ± 0.001 14.99 ± 0.002 6.06 ± 0.003

Key: Sample A – Control, Sample B – 1 hour drying, Sample C – 2 hours drying

and Sample D – 3 hours drying

4.4 Moisture Content of Smoked and Dried Fish Fillets during Storage.

The moisture content of different samples of the smoked and dried fish fillets

was checked everyday during the storage period of 21 days and shown in Table 2

From the result shown in Table 2, there were progressive decreases in moisture

content of fish fillets during the 21 days of storage. For instance Sample A decreased

from 48.74 to 31.46%, Sample B decreased from 46.16 to 30.91, Sample C decreased

from 44.93 to 30 .13 and Sample D decreased from 43.44 to 20.15.

As observed by Ikeme and Gugnani (1988), smoking and drying time affect the

moisture content of fish. Control A had the lowest rate of decrease and high values for

moisture content while sample D recorded the highest rate of decrease and low values

for moisture content. This is to say that moisture content of the samples decreased with

drying time and storage period as a result of loss of water from the surface of fish to the

atmosphere.

27

Table 2: Effect of storage on the moisture content of different samples of the

smoked and dried fish fillet

DAYS SAMPLE A SAMPLE B SAMPLE C SAMPLE D

Day 1 48.736 ± 0.003 46.16 ± 0.002 44.93 ± 0.004 43.44 ± 0.002

2 45.43 ± 0.026 45.22 ± 0.020 44.18 ± 0.021 41.75 ± 0.010

3 44.93 ± 0.002 43.72 ± 0.025 43.35 ± 0.004 41.32 ± 0.015

4 44.31 ± 0.015 42.52 ± 0.025 41.72 ± 0.025 40.63 ± 0.015

5 41.86 ± 0.010 41.25 ± 0.030 40.63 ± 0.026 39.08 ± 0.074

6 40.08 ± 0.070 38.49 ± 0.015 38.42 ± 0.021 34.63 ± 0.025

7 38.63 ± 0.012 38.32 ± 0.021 38.12 ± 0.021 34.05 ± 0.033

8 38.26 ± 0.031 37.92 ± 0.025 36.43 ± 0.026 33.23 ± 0.030

9 37.38 ± 0.015 36.32 ± 0.015 36.07 ± 0.064 33.12 ± 0.075

10 36.31 ± 0.021 36.25 ± 0.031 35.82 ± 0.010 32.44 ± 0.082

11 36.67 ± 0.021 35.92 ± 0.021 35.63 ± 0.026 30.55 ± 0.010

12 35.86 ± 0.010 35.58 ± 0.012 35.52 ± 0.026 29.86 ± 0.015

13 35.63 ± 0.010 35.43 ± 0.010 35.41 ± 0.015 29.81 ± 0.015

14 35.46 ± 0.020 35.37 ± 0.015 35.22 ± 0.020 29.63 ± 0.030

15 35.29 ± 0.070 35.25 ± 0.006 35.17 ± 0.021 29.52 ± 0.021

16 35.22 ± 0.020 35.08 ± 0.072 34.64 ± 0.021 27.94 ± 0.015

17 34.94 ± 0.015 34.29 ± 0.015 33.62 ± 0.015 26.43 ± 0.021

18 33.58 ± 0.020 33.50 ± 0.010 32.82 ± 0.020 26.37 ± 0.010

19 33.29 ± 0.025 32.73 ± 0.025 30.86 ± 0.015 25.46 ± 0.015

20 31.56 ± 0.010 31.14 ± 0.118 30.33 ± 0.010 20.40 ± 0.015

21 31.46 ± 0.006 30.91 ± 0.025 30.13 ± 0.010 20.15 ± 0.015

Key: Sample A – Control, Sample B – 1 hour drying, Sample C – 2 hours drying and

Sample D – 3 hours drying

4.5 Effect of Storage on the Water Activities of Smoked and Dried Fish Fillets

The water activity of the smoked and dried fish fillets during the storage period

of 21 days is shown in table 3. As smoking commenced, drying also started. During the

period of drying moisture is lost, thereby decreasing water activity (aw).

Table 3 shows the effect of storage period on water activity; which is a measure

of the activity of water still present in the fish which can enhance chemical activity or

28

support microbial growth and activities in the smoked and dried fish fillets samples.

Water activity (aw) level dropped progressively with increase in drying time and with

the storage period.

Table 3: Effect of storage on the water activities of smoked and dried fish fillets.

DAYS SAMPLE A SAMPLE B SAMPLE C SAMPLE D

0 Day 0.925 0.007 0.915 0.007 0.915 0.007 0.905 0.004

2nd

Day 0.885 0.007 0.875 0.008 0.850 0.001 0.825 0.007

4th

Day 0.875 0.008 0.860 0.014 0.840 0.001 0.810 0.006

6th

Day 0.845 0.007 0.840 0.007 0.815 0.006 0.805 0.005

8th

Day 0.830 0.014 0.815 0.021 0.745 0.007 0.735 0.007

10th

Day 0.785 0.007 0.655 0.007 0.638 0.005 0.635 0.007

12th

Day 0.760 0.007 0.640 0.014 0.630 0.001 0.625 0.006

14th

Day 0.640 0.014 0.635 0.006 0.625 0.007 0.580 0.028

16th

Day 0.635 0.035 0.625 0.007 0.615 0.021 0.550 0.001

18th

Day 0.625 0.007 0.615 0.021 0.550 0.001 0.535 0.022

20th

Day 0.615 0.021 0.610 0.021 0.535 0.021 0.525 0.022

21st Day 0.560 0.028 0.555 0.007 0.530 0.014 0.505 0.007



4.6 Effect of storage on the thiobarbituric (tba) value of the smoked and dried

fish fillets

Table 4 shows that samples were affected by the storage period and drying time.

The TBA value of dried and undried samples varied. The TBA values for smoked and

dried samples were consistently lower than those of control sample (A) which was not

dried. Low value of TBA value on the 1st day could probably be due to the destruction

of pro-oxidants like haematin compounds and lipase enzyme responsible for hydrolytic

rancidity during smoking, drying and also due to anti-oxidative effect of phenol. All

samples showed increased TBA values during storage period and it was also known

that fatty fishes like mackerel are prone to oxidative rancidity with storage. This is in

agreement with the reports of Pratt and Watts (1964) and Lee et al., (1986).

29

Thiobarbituric acid (TBA) value measures the formation and consumption of

malonaldehyde type of carbonyl oxides during lipid oxidation and lipid-protein

interactions leading to non enzymic browning of fish.

Table 4: Effect of storage on the Thiobarbituric (TBA) value of the smoked and

dried fish fillet

SAMPLE 1ST

DAY 7TH

DAY 14TH

DAY 21ST

DAY

A 0.938 0.002 1.089 0.003 1.795 0.004 2.493 0.003

B 0.633 0.003 0.784 0.003 1.562 0.002 2.265 0.003

C 0.467 0.004 0.707 0.003 1.406 0.003 2.028 0.002

D 0.391 0.002 0.625 0.003 1.253 0.001 1.565 0.004



4.7 Effect of Storage on the Peroxide Value of Smoked and Dried Fish Fillet

From Table 5 below, peroxide value increased with storage period showing that

fatty fishes are prone to oxidative rancidity with storage but decreases with drying time.

As oxidation of fat takes place in the fish sample, the double bond of the unsaturated

fatty acids is attached forming peroxides. These peroxides then break down forming

secondary oxidation products, which indicate rancidity in fish samples. From this

research work it was observed that the peroxide values of the different samples

increased as follows; Sample A increased from 5.64 – 14.43, Sample B increased from

5.11 – 13.55, Sample C increased from 4.76 – 12.23 and Sample D increased from 4.41

– 11.94. The peroxide value is normally used as an indicator of deterioration of fat.

Table 5: Effect of storage on the peroxide value of smoked and dried fish fillets

SAMPLE 1ST

DAY 7TH

DAY 14TH

DAY 21ST

DAY

A 5.64 0.015 8.62 0.020 11.62 0.021 14.43 0.031

B 5.11 0.067 8.53 0.036 10.42 0.025 13.55 0.010

C 4.76 0.015 6.45 0.021 10.23 0.021 12.23 0.030

D 4.41 0.021 6.24 0.032 10.13 0.021 11.94 0.015



30

4.8 Effect of Storage on Total Viable Count (TVC) (cfu/g) of Smoked and

Oven- Dried Fish Fillets

During storage, there was more rapid proliferation of microorganisms in the undried

Sample A (control) while the oven dried samples had lower microbial growth which

decreased with drying time. As storage period advanced, the total microbial counts

were very similar for the smoked and oven-dried for 1 and 2 hrs drying with the 3 hrs

oven dried products maintaining lower counts. The microbial flora appeared to be

mainly moulds and yeasts. This observation on microbial types agree with the finding

of Ikeme and Uwaegbute (1988) that the mackerel dipped in brine solution of more

than 15% has a lower microbial load than those with lower brine concentration. The

lower growth rates during storage of oven dried sample also agree with the report of

Schafer (1990) that the drying which takes place during smoking aids removal of water

available for microbial growth, thereby retarding microbial growth while prolonging

the product shelf life.

The Total viable count (TVC) of the smoked and oven- dried fish fillet is

recorded in Table 6. It shows the microbial counts in the various oven – dried samples

and on the smoked control sample.

Table 6: Effect of storage on total viable count (TVC) (cfu/g) of smoked and dried

fish fillets

SAMPLE 1ST

DAY 7TH

DAY 14TH

DAY 21ST

DAY

A 1.615 x 103 1.92 x 10

5 1.04 x 10

7 1.83 x 10

8

B 1.295 x 103 1.955 x 10

5 4.8 x 10

6 1.375 x 10

8

C 1.050 x 103 1.44 x 10

5 3.935 x 10

6 5.725 x 10

7

D 8.28 x 102 1.145 x 10

5 3.025 x 10

6 4.12 x 10

7



4.9 Effect of Storage on Mould Count (cfu/g)of Smoked and Dried Fish Fillets

From Table 7, it was noted that mould count on the various fish samples

increased with the storage period but decreased with the drying time. The faster rate of

mould count increase for Sample A (control) and also in Sample B may be due to high

moisture content and water activity (aw) of Sample A and B compared to sample C and

D. These findings support reports by Awan and Okaka (1985) and Schafer (1990) that

smoking associated with drying removes water available to microbes. Awan and Okaka

31

(1985) noted that above 2% moisture level, mould growth can be anticipated if the

environment is favourable.

The mould count of the smoked and dried fish fillet during a storage period of

21 days is recorded in Table 7.

Table 7: Effect of storage on mould counts (cfu/g)of smoked and dried fish fillets

SAMPLES 1ST

DAY 7TH

DAY 14TH

DAY 21ST

DAY

A 1.2 x 102 1.38 x 10

3 6.7 x 10

3 1.825 x 10

4

B 6.1 x 10 7.29 x 102 4.6 x 10

3 7.0 x 10

3

C 3.8 x 10 4.05 x 102 3.2 x 10

3 6.85 x 10

3

D 1.1 x 10 2.32 x 102 9.6 x 10

2 5.55 x 10

3



4.10: Sensory Characteristics of Smoked and Dried Fish Fillet

From the sensory quality scores, we can observe that sample D gave more

pronounced appearance, colour, taste and general acceptability to a reasonable extent

before it started deteriorating. The rancidity increase with reduced moisture content was

as a result of increase in lipid oxidation rate and this affected the general acceptability

scores at the later stage of storage.

Table 8: Changes in the appearance of smoked and dried fish fillets during

storage*+

Storage period (days)

Sample 0 7 14 21

A 6.9a 0.32 6.0

b 0.00 2.0

c 0.00 1.4

c 0.52

B 7.0a 0.00 6.0

b 0.00 3.5

b 1.08 2.1

b 0.32

C 7.0a 0.00 6.1

b 0.32 4.0

b 0.00 2.5

b 0.85

D 7.0a 0.00 6.8

b 0.42 4.6

a 0.52 4.0

a 0.00



* Mean values in the same column bearing different superscripts are

significantly different (p < 0.05).

+ Values are mean Standard Deviation of ten (10) panelists.

32

Table 9: Changes in the saltiness of smoked and dried fish fillets during storage*+


Sample 0 7 14 21

A 4.20b 0.63 5.0a 0.00 5.1a 0.32 5.0a 0.00

B 5.8a 1.93 5.0a 0.00 5.1a 0.32 5.0a 0.00

C 4.8ab

0.42 5.1a 0.32 5.1a 0.32 5.0a 0.00

D 4.9ab

1.19 5.1a 0.32 5.1a 0.67 5.2a 0.79






Table 10: Changes in the flavour of smoked and dried fish fillets during storage*+


Sample 0 7 14 21

A 6.8a 0.42 6.0b 0.00 5.0b 0.00 3.2c 0.03

B 6.9a 0.32 6.0b 0.00 5.0b 0.00 4.0b 0.67

C 6.9a 0.32 6.3b 0.48 5.0b 0.00 4.3b 0.67

D 6.9a 0.32 6.8b 0.42 5.4a 0.52 5.7a 0.67






Table 11: Changes in the colour of smoked and dried fish fillets during storage*+


Sample 0 7 14 21

A 6.9a 0.32 4.8b 0.42 3.2b 0.63 2.0c 0.00

B 7.0a 0.00 4.8b 0.42 3.5b 0.85 2.1c 0.32

C 7.0a 0.32 5.2b 0.63 5.0a 0.00 3.1b 0.32

D 7.0a 0.00 5.9b 0.32 5.2a 0.42 4.1a 0.88






33

Table 12: Changes in the taste of smoked and dried fish fillets during storage*+


Sample 0 7 14 21

A 6.9a 0.31 6.8ab 0.42 3.4d 0.70 3.0d 0.00

B 7.0a 0.00 7.0a 0.00 4.4c 0.52 4.0c 0.47

C 7.0a 0.00 6.6b 0.52 5.0b 0.00 4.9b 0.32

D 7.0a 0.00 7.0a 0.00 5.8a 0.42 5.6a 0.70






Table 13: Changes in the general acceptability of smoked and dried fish fillets

during storage*+


Sample 0 7 14 21

A 6.9a 0.32 6.2b 0.42 3.4c 0.70 3.0d 0.00

B 7.0a 0.00 6.2b 0.42 4.3b 0.67 4.0c 0.47

C 7.0a 0.00 6.8a 0.42 5.1a 0.32 5.0a 0.00

D 7.0a 0.00 7.0a 0.00 5.6a 0.52 5.6a 0.52

Key: Sample A – Control, Sample B – 1 hour drying, Sample C – 2 hours drying, and





34

CHAPTER FIVE

CONCLUSION AND RECOMMENDATION

5.1 Conclusion

The results of this research, which was based on smoked and dried samples of

fish, showed that oven drying when used in smoked mackerel fish fillets led to

consistent decrease in the moisture content and water activity of the fish. General

acceptability, flavour, appearance and colour scores were highest for products with low

moisture content. Sample D that was dried for 3 hours had the best flavour, taste and

overall keeping quality during storage period, followed by sample C that was dried for

2 hours when compared with sample B and A (control). Therefore, the present study

demonstrates that smoking and drying treatments applied to fish samples play great

roles in preserving and prolonging the shelf stability of fish. It also aids in shelf life

extension of the fish and also maintenance of its consumer appeal and acceptability.

Mould and total viable counts decreased with the varying drying time, with sample D

(dried for 3 hours) being the sample with the lowest mould count showing that the

longer the oven drying the lower the microbial growth and the longer the shelf life of

the mackerel fish. The interplays of the physicochemical, the chemical and

microbiological changes during oven drying and ambient storage affected the sensory

quality of smoked fish. Prolonged ambient storage up to 21 days reduced the

organoleptic quality of all treatments. This long ambient storage up to 21 days reduced

the general quality (stability) and acceptability of smoked and dried mackerel fish

fillets.

From this result, it can be inferred that smoking and oven-drying as methods of

preservation can be adopted in extending the shelf life of fish, especially in developing

countries where all the required sophisticated storage equipment are not available.

However, oven drying of smoked fatty fish like mackerel should be best if the drying

time is increased and should not be stored up to 21 days under ambient temperature to

prevent deterioration in quality especially organoleptic quality.

35

5.2 Recommendation

The smoking time should be increased likewise the drying time in order

to reduce more moisture from the fish.

More work should be done to determine suitable low cost `packaging

materials for smoked and dried fish in order to avoid recontamination of

fish after processing.

Other treatments (like the use of preservatives ie whether natural or by

use of chemicals) should be applied to increase the shelf stability and

general acceptability of the product.

36

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40

APPPENDICES

APPENDIX I

DIMENSIONS OF THE FRESH FISH

NO OF FISHES LENGTH (cm) WEIGHT (g)

1 33 500

2 32 500

3 31 400

4 31 400

5 32 400

6 30 200

7 32 200

8 20 200

9 29 200

10 29 200

Total 309 3200

Average 30.9 320

Range 29 – 33 200 – 500

41

APPENDIX II

DIMENSIONS OF THE DRESSED FISH FILLETS

NO OF FISH FILLETS LENGTH (cm) WEIGHT (g)

1 22 100

2 22 100

3 22 100

4 22 100

5 20 99

6 22 100

7 20 80

8 20 80

9 23 100

10 22 100

11 20 90

12 19 80

13 22 100

14 19 80

15 19 70

16 17 60

17 18 60

18 19 80

19 20 90

20 20 90

TOTAL 408 1759

AVERAGE 20.4 87-95

RANGE 17 – 23 60 – 100

42

APPENDIX III

WET AND DRY BULB TEMPERATURE AND RELATIVE HUMIDITY OF

DIFFERENT DAYS OF SMOKED AND DRIED FISH FILLETS DURING STORAGE.

DAYS WET BULB DRY BULB RELATIVE

HUMIDITY

1 31 36 69

2 30 34 74

3 29 34 68

4 32 36 75

5 28 36 45

6 28 39 41

7 29 30 93

8 36 38 87

9 28 36 53

10 29 36 58

11 28 39 45

12 30 36 63

13 36 28 85

14 30 34 74

15 28 31 79

16 30 36 63

17 28 34 62

18 26 30 72

19 30 33 80

20 28 36 53

21 28 34 62

TOTAL 622 728 1401

AVERAGE 29.619 34.667 66.714

RANGE 26 – 36 28 – 39 41– 93

43

APPENDIX IV

SAMPLE SCORE SHEET USED BY TASTE PANEL

Sample No……………………………..

Date…………..………………………. Score……………………….

You are provided with four different samples. Please indicate the sample

number and evaluate or score the sample according to the quality of Appearance,

saltiness, flavour colour, taste and general acceptability. Before testing each sample

take a sip of water and rinse your mouth, pause for a minute before tasting the next

sample.

Parameters 1 2 3 4 5 6 7

Appearance Extremely

bad

Very bad Moderately

bad

Neither

good nor

bad

Moderately

good

Very good Extremely

good

Saltiness Extremely

bland

Very bland Moderately

bland

Neither

bland nor

salty

Moderately

salty

Very salty Extremely

salty

Flavour Extremely

bad

Very bad Moderately

bad

Neither

good nor

bad

Moderately

good

Very good Extremely

good

Colour Extremely

undesirable

Very

undesirable

Moderately

undesirable

Neither

undesirably

nor desirable

Moderately

desirable

Very

desirable

Extremely

desirable

Taste Extremely

good

Very good Moderately

good

Neither

good nor

bad

Moderately

bad

Very bad Extremely

bad

Gene-

acceptability

Extremely

acceptable

Very

acceptable

Moderately

acceptable

Neither

acceptable

nor

unacceptable

Moderately

unacceptable

Very

unacceptable

Extremely

unacceptable

44

APPENDIX V

ANOVA FOR APPEARANCE OF SMOKED AND DRIED FISH FILLETS

Parameters Source of variation Sum of

square

Df Mean

square

F Sig.

Appearance A

Between groups 0.075 3 0.025 1.000 0.404

Within groups 0.900 36 0.005

Total 0.975 39

Appearance B

Between groups 4.476 3 1.492 21.480 0.578


Total 6.975 39

Appearance C

Between groups 37.075 3 12.358 34.488 0.000


Total 49.975 39

Appearance D

Between groups 36.200 3 12.067 44.327 0.000


Total 46.00 39

45

APPENDIX VI

ANNOVA FOR SALTINESS

Parameters Source of variations Sum of square Df Mean

square

F Sig.

Saltiness A

Between groups 13.075 3 4.358 3.763 0.019


Total 54.775 39

Saltiness B

Between groups 0.100 3 0.033 0.667 0.578


Total 1.900 39

Saltiness C

Between groups 0.300 3 0.100 0.529 0.665


Total 7.100 39

Saltiness D

Between groups 0.300 3 0.100 0.643 0.592


Total 5.900 39

46

APPENDIX VII

ANNOVA FOR FLAVOUR

Parameters Source of variation Sum of square Df Mean square F Sig

Flavour A

Between groups 0.075 3 0.025 0.209 0.889


Total 4.375 39

Flavour B

Between groups 4.275 3 1.425 13.865 0.000


Total 7.975 39

Flavour C

Between groups 1.200 3 0.400 6.00 0.002


Total 3.600 39

Flavour D

Between groups 32.600 3 10.867 17.945 0.000


Total 54.400 39

47

APPENDIX VIII

ANNOVA FOR COLOUR


Colour A

Between groups 0.075 3 0.025 1.00 0.404


Total 0.975 39

Colour B

Between groups 8.075 3 2.692 12.584 0.000


Total 15.775 39

Colour C

Between groups 31.276 3 10.425 32.077 0.000


Total 42.975 39

Colour D

Between groups 29.075 3 9.692 40.103 0.000


Total 37.775 39

48

APPENDIX IX

ANNOVA FOR TASTE


Taste A

Between groups 0.075 3 0.025 1.000 0.404


Total 0.975 39

Taste B

Between groups 1.100 3 0.367 3.300 0.031


Total 5.100 39

Taste C

Between groups 30.700 3 10.233 43.857 0.000


Total 39.100 39

Taste D

Between groups 38.075 3 12.692 62.589 0.000


Total 45.37539

49

APPENDIX X

ANNOVA FOR GENERAL ACCEPTABILITY

Parameters Source of

variation

Sum of square Df Mean square F Sig

General Acceptability A

Between groups 0.075 3 0.025 1.000 0.404


Total 0.975 39

General Acceptability B

Between groups 5.100 3 1.700 12.750 0.000


Total 9.900 39

General Acceptability C

Between groups 27.800 3 9.267 28.271 0.000


Total 39.600 39

General Acceptability D

Between groups 39.200 3 13.067 106.909 0.000


Total 43.600 39

50

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