ABSTRACT

This study designed, fabricated and evaluated drying performance of a solar fish dryer. Fish samples (225g each) were processed using open sun drying (CCC), fabricated solar dryer (BBB) and smoke drying (DDD). The unprocessed sample (AAA) served as the control. Samples were randomly assigned to the three (3) drying methods and replicated twice. Samples were analyzed for proximate, microbiological, physiochemical, vitamins and mineral composition, using standard labouratory procedures. Data were also collected for organoleptic properties. Data obtained were subjected to the analysis of variance. Decrease in moisture content was observed during processing using the various drying methods until samples attained constant weight within 40-64hours. The proximate composition of the fish samples were significantly (p≤0.05) affected by the different drying methods. Moisture ranged from 10.05-40.95%, indicating potentials for storage stability for sample BBB and CCC. Carbohydrate, Crude fibre and ash were generally low while protein and fat were high ranging from 37.48%-55.61% and 16.20%-30.30% respectively. AAA and CCC showed significantly (p≤0.05) higher microbial load on both the nutrient agar and macConkey agar. pH of samples was not significantly (p≤0.05) affected by drying methods. The free fatty acid and peroxide values of the samples ranged from 1.38-5.02Mg/KOH/g and 1.10-2.90Mg/Kg respectively. These were generally higher in CCC, indicating its potency to develop off flavor. The different processors used significantly (p≤0.05) affected the level of acceptability of the samples by the panelists. DDD recorded the highest level of acceptance among the samples, followed by BBB, CCC and AAA respectively.

TABLE OF CONTENTS

                                                                                                                              Page

Title page                                                                                                                    i

Declaration                                                                                                                  ii

Certification                                                                                                                iii

Dedication                                                                                                                  iv

Acknowledgement                                                                                                      v

Table of Content                                                                                                         vi

List of Tables                                                                                                              xi

List of Figures                                                                                                             xii

List of Plate                                                                                                                xiii

Abstract                                                                                                                      xiv

CHAPTER 1: INTRODUCTION                                                             

1.1  Background of  Study                                                                                            1

1.2 Statement of Problem                                                                                           6

1.3 Justification                                                                                                           6

1.4 Objective of Study                                                                                               7

CHAPTER 2: LITERATURE REVIEW                                                 

2.1 Fish                                                                                                                       9

2.1.1 Group of fishes                                                                                                  11

2.1.2 Types of fishes                                                                                                   12

2.1.2.1 Common carp                                                                                                  12

2.1.2.2 Atlantic cod                                                                                                    12

2.1.2.3 African catfish                                                                                                            13

2.1.2.4 Atlantic mackerel                                                                                            13

2.1.2.5 Tilapia fish                                                                                                      13

2.1.2.6 Bony fish                                                                                                        14

2.1.2.7 Salmon fish                                                                                                     14

2.1.3 Sources and origin of common Fishes                                                               14

2.1.4 Fish cultivation in Africa                                                                                   15

2.2 Fish Spoilage and Causes                                                                                     17

2.2.1 Post harvest fish losses                                                                                      17

2.2.2 Autolysis                                                                                                            18

2.2.3 Bacteria                                                                                                              19

2.2.4 Rancidity                                                                                                           21

2.2.5 Mechanical damage                                                                                           21

2.3 Methods of Fish Preservation                                                                               21

2.3.1 Salting                                                                                                                23

2.3.2 Cold storage method of fish preservation                                                         23

2.3.3 Frying method of fish preservation                                                                   25

2.3.4 Canning method of fish preservation                                                                26

2.4 conventional Drying Methods                                                                              27

2.5 Drying Methodology                                                                                            28

2.5.1        Natural drying methods                                                                                  29

2.5.1.1 Direct method                                                                                                 30

2.5.1.2 Indirect method                                                                                              31

2.5.1.3 Green house solar dryer                                                                                  32

2.5.2 Artificial drying methods                                                                                  33

2.5.2.1 Convective drying                                                                                          33

2.5.2.2 Drying by radiation                                                                                         34

2.5.2.2 Freeze drying                                                                                                  34

2.5.2.3 Osmotic drying                                                                                               36

2.6 Quality Loss of Traditionally Dried Fish                                                              37

2.7 Drying Kinetics and Modelling                                                                            38

2.7.1 Effect of air temperature and air velocity on drying kinetics                            40

2.7.2 Effect of shape on drying kinetics                                                                     41

2.7.3 Effect of pre-treatment on drying kinetics                                                        42

2.7.4 Effect of relative humidity on drying kinetics                                                  43

2.8 Commercial Dried Products                                                                                 44

2.8.1 Dried meat products                                                                                          44

2.8.2 Powdered products                                                                                            45

2.8.3 Drying of cereals and pulses                                                                              46

2.8.4 Dried cultures                                                                                                    46

2.8.5 Dried fruits and vegetables                                                                                47

2.9 Effect of Smoking Methods on Quality of Fish                                                   47

2.9.1 Hot smoke                                                                                                          50

2.9.2 Open fire smoking                                                                                             52

2.9.3 Cold smoking                                                                                                     52

2.11 Effects of sun and oven drying on fish                                                              53

CHAPTER 3: MATERIALS AND METHODS                                                  

3.1 Materials                                                                                                               54

3.2 Methods                                                                                                                54

3.2.1 Construction of the solar dryer                                                                          54

3.2.1.1 Drying chamber                                                                                              55

3.2.1.2  Cover plate                                                                                                      55

3.2.1.3  Cover                                                                                                              55

3.2.1.4  Air gap (inlet and outlet)                                                                                55

3.2.1.5  Drying tray                                                                                                      55

3.2.1.6  Orientation of solar collector (glass)                                                               56

3.2.1.7  Angle of tilt of solar collector                                                                         56

3.2 Expected Heat Flux that will be generated by the Fabricated Dryer                   57

3.2.1 Minimum expected heat flux that will be generated by the dryer

within                                                                                                                 57

3.2.2 Maximum expected heat flux that will be generated by the dryer                    58

3.2.3 Average expected heat flux that will be generated by the dryer

within Umuahia region                                                                                      59

3.3 Performance Evaluation of the Solar Dryer                                                         59

3.3.1 Conventional open sun dried fishes                                                                   59

3.3.2 Drying of the fish with fabricated solar dyer                                                    59

3.3.3 Smoking of fish                                                                                                 59

3.4 Determination of Proximate Composition                                                            60

3.4.1 Determination of moisture content                                                                    60

3.4.2 Determination of ash content                                                                            60

3.4.3 Determination of fat content                                                                             61

3.4.4 Determination of protein content                                                                      61

3.4.5 Determination of crude fiber content                                                                62

3.4.6 Determination of carbohydrate content                                                             62

3.5              Determination of Physicochemical Properties                                                63

3.5.1 pH determination                                                                                               63

3.5.2        Peroxide values                                                                                               63

3.5.3 Determination of free fatty acid content                                                           64

3.6 Sensory Evaluation                                                                                               64

3.7 Microbiological Determination                                                                             65

3.8 Determination of Vitamin Composition                                                               65

3.8.1 Vitamin B1 (thiamin) determination                                                                  66

3.8.2 Vitamin A (retinol) determination                                                                     66

3.8.3 Vitamin C determination                                                                                   66

3.9 Determination of Mineral Composition                                                                67

3.10 Statistical Analysis                                                                                              68

CHAPTER 4: RESULTS AND DISCUSSIONS                                                 

4.1 Drying Characteristics of Fish Samples                                                                69

4.2 Proximate Composition of Fish Samples                                                              73

4.3 Physicochemical Properties                                                                                   78

4.4 Microbiological Quality                                                                                        81

4.5 Vitamin Composition                                                                                            83

4.6 Mineral Composition                                                                                            85

4.7 Sensory Quality of Fresh and Processed Fish Samples                                        87

CHAPTER 5: CONCLUSION AND RECOMMENDATIONS                        

5.1 Conclusion                                                                                                            90

5.2 Recommendations                                                                                                90

References                                                                                                            91

Appendix                                                                                                              99

LIST OF TABLES

4.1 Drying characteristics of fish samples                                                                  70

4.2 Proximate Composition of Fresh and Dried Fish Sample                        77

4.3  Physiochemical Properties of Fresh and Dried Fish Sample                                80

4.4  Total Plate Count (CFU/g) of Fresh and Dried Fish Sample                               82

4.5 Vitamin Composition of Fresh and Processed Fish Sample                                 84

4.6 Mineral Composition of Fresh and Processed Fish Sample                                  86

LIST OF FIGURES

3.1 One Chamber Cabinet Solar Dryer                                                                       57

4.1 Drying Curve                                                                                                        72

4.7 Mean Sensory Properties Scores of the Fish Samples                                          88

LIST OF PLATES

1: Photo of Fabricated Dryer                                                                                      89