Microbiology and Spoilage Trail in Nile Perch (Lates niloticus), Lake ...

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iv TABLE OF CONTENTS DECLARATION ........................................................................................................................ I DEDICATION ........................................................................................................................... II ABSTRACT ............................................................................................................................. III 1 INTRODUCTION .............................................................................................................. 1 1.1 QUALITY AND SAFETY ASSURANCE OF EXPORTED FISH AND FISH PRODUCTS FROM TANZANIA ................. 2 1.2 JUSTIFICATION OF THE STUDY ....................................................................................................................... 4 1.2.1 Objectives............................................................................................................................................. 5 2 BACK GROUND ............................................................................................................... 7 2.1 MICROBIOLOGICAL SAFETY HAZARDS IN FISH INDUSTRY ............................................................................. 7 2.2 RIGOR MORTIS AND POST HARVEST STORAGE OF FRESH FISH IN ICE .......................................................... 9 2.3 FRESH FISH SPOILAGE .................................................................................................................................... 9 2.3.1 Microbiological spoilage of fresh fish ................................................................................................ 10 2.3.2 Biochemical spoilage of fresh fish ...................................................................................................... 14 2.4 STAGES OF SPOILAGE FOR ICED FRESH FISH ............................................................................................... 16 2.5 FACTORS CONTRIBUTING ON FISH SPOILAGE ............................................................................................. 18 2.5.1 Temperature ...................................................................................................................................... 19 2.6 METHODS FOR ASSESSMENT OF FRESH FISH QUALITY ............................................................................... 22 2.6.1 Sensory (qualitative) methods ........................................................................................................... 22 2.6.2 Physical methods ............................................................................................................................... 23 2.6.3 Microbiological methods ................................................................................................................... 24 2.6.4 Chemical methods ............................................................................................................................. 26 3 MATERIALS AND METHODS ..................................................................................... 28 3.1 STUDY AREA AND SAMPLING PLAN ............................................................................................................. 28 3.2 SAMPLING .................................................................................................................................................... 29 3.2.1 Phase I: Microbiology of Water, Sediments and Nile Perch. ............................................................. 29 3.2.2 Phase II: Shelf life for Laboratory iced whole Nile perch and chilled fillets ....................................... 30 3.2.3 Phase III: Microbiology of whole Nile perch swabs, on line fillets and shelf life of establishments chilled fillets ..................................................................................................................................................... 31 3.3 PROCEDURES ............................................................................................................................................... 32 3.3.1 Sensory (orgnoleptic) assessment ..................................................................................................... 32 3.3.2 Microbiological analysis ..................................................................................................................... 33 3.3.3 Chemical analysis ............................................................................................................................... 39 3.3.4 Data analysis ...................................................................................................................................... 39
4 RESULTS......................................................................................................................... 40 4.1 PHASE I: MICROBIOLOGY OF WATER, SEDIMENTS AND WHOLE NILE PERCH ............................................. 40 4.1.1 Phase I trial 1: Water .......................................................................................................................... 40 4.1.2 Phase I trial 2: Sediments ................................................................................................................... 41 4.1.3 Phase I trial 3: Whole Nile perch ........................................................................................................ 41 4.2 PHASE II: SHELF LIFE OF LABORATORY ICED WHOLE NILE PERCH AND CHILLED FILLETS ............................ 43 4.2.1 Phase II trial 1: Shelf life of iced whole Nile perch ............................................................................. 43 4.2.2 Phase II trial 2: Shelf life of laboratory chilled Nile perch fillets ........................................................ 47 4.3 PHASE III: MICROBIOLOGY OF WHOLE NILE PERCH SWABS, ON LINE FILLETS AND SHELF LIFE OF ESTABLISHMENTS CHILLED FILLETS ....................................................................................................................... 49 4.3.1 Phase III - Trial 1: Microbiology of whole Nile perch swabs and online fillets ................................... 49 4.3.2 Phase III – Trial 2: Shelf life of establishments chilled fillets .............................................................. 51 4.4 PRESUMPTIVE SSOs ..................................................................................................................................... 56 4.5 SHELF LIFE OF ICED WHOLE NILE PERCH AND CHILLED FILLETS .................................................................. 57 5 DISCUSSION .................................................................................................................. 58 5.1 PHASE I: NATURAL MICROBIOLOGY OF WATER, SEDIMENTS AND WHOLE NILE PERCH ............................ 58 5.1.1 Phase I trial 1: Water .......................................................................................................................... 58 5.1.2 Phase I trial 2: Sediments ................................................................................................................... 58 5.1.3 Phase I trial 3: Whole Nile perch ........................................................................................................ 59 5.2 PHASE II: SHELF LIFE OF LABORATORY ICED WHOLE NILE PERCH AND CHILLED FILLETS ............................ 59 5.2.1 Phase II trial 1: Shelf life of iced whole Nile perch ............................................................................. 59 5.2.2 Phase II trial 2: Shelf life of laboratory chilled fillets .......................................................................... 62 5.3 PHASE III: MICROBIOLOGY OF WHOLE NILE PERCH SWABS, ON LINE FILLETS AND SHELF LIFE OF ESTABLISHMENTS CHILLED FILLETS ....................................................................................................................... 63 5.3.1 Phase III - Trial 1: Microbiology of whole Nile perch swabs and online fillets ................................... 63 5.3.2 Phase III – Trial 2: Shelf life of establishments chilled Nile perch fillets ............................................ 65 5.4 PRESUMPTIVE SSO ....................................................................................................................................... 68 6 CONCLUSIONS AND RECOMMENDATION ............................................................. 69 6.1 CONCLUSIONS ............................................................................................................................................. 69 6.2 RECOMMENDATION .................................................................................................................................... 70 ACKNOWLEDGEMENT ....................................................................................................... 71 REFERENCES ......................................................................................................................... 72 APPENDICES .......................................................................................................................... 83 v
Page 1 and 2: 1 Microbiology and Spoilage Trail i
Page 3 and 4: i DECLARATION I wish to declare tha
Page 5: iii ABSTRACT The microbiological sp
Page 9 and 10: vii LIST OF TABLES TABLE 1: NILE PE
Page 11 and 12: East Africa. The lake produces a fi
Page 13 and 14: Table 1: Nile perch export processi
Page 15 and 16: 1.2.1.3 Output from the study The i
Page 17 and 18: eservoir i.e. Salmonella, Shigella,
Page 19 and 20: Spoilage of food means to deprive i
Page 21 and 22: • Pseudomonas and Shewanella putr
Page 23 and 24: NH3 Ammonia amino acids and urea Ac
Page 25 and 26: According to Cornell, (1975), the p
Page 27 and 28: as well as indices of fish spoilage
Page 29 and 30: Table 6: Cardinal temperature for m
Page 31 and 32: is insufficient for good quality an
Page 33 and 34: which are posing difficulties in de
Page 35 and 36: Vibrionaceae at higher temperatures
Page 37 and 38: 3 MATERIALS AND METHODS 3.1 STUDY A
Page 39 and 40: 3.2.1.2 Phase I- trial 2: Sediments
Page 41 and 42: 3.2.3.2 Phase III - trial 2: Shelf
Page 43 and 44: • Total viable counts (TVC): Volu
Page 45 and 46: 3.3.2.1.3 Phase I - Trial 3: Whole
Page 47 and 48: 3.3.2.2.2 Phase II trial 2: Shelf l
Page 49 and 50: 4 RESULTS 4.1 PHASE I: MICROBIOLOGY
Page 51 and 52: Table 15: Pathogenic microorganisms
Page 53 and 54: The excellent freshness fish grade
Page 55 and 56: Figure 7: Changes of specific spoil
Page 57 and 58:
4.2.2.2 Chemical analysis Changes o
Page 59 and 60:
Figure 14: Whole Nile perch in stai
Page 61 and 62:
21mgN/100g from days 12-15 which co
Page 63 and 64:
4.3.2.3 Establishment E3 - chilled
Page 65 and 66:
The results from chilled fillets (f
Page 67 and 68:
5 DISCUSSION 5.1 PHASE I: NATURAL M
Page 69 and 70:
etween 15-20 days (2-3 weeks). Henc
Page 71 and 72:
the components contributing to TVB-
Page 73 and 74:
ice there was only a small margin (
Page 75 and 76:
(around 6 log10 cfu/g) after 12 sto
Page 77 and 78:
5.4 PRESUMPTIVE SSO There are two t
Page 79 and 80:
6.2 RECOMMENDATION 1. Similar shelf
Page 81 and 82:
REFERENCES Adams M. R. and Moss, M.
Page 83 and 84:
Doyle M. P., (1990): Pathogenic Esc
Page 85 and 86:
Huss, H. H. and Larsen A., (1980):
Page 87 and 88:
Liston J, (1992): Bacterial spoilag
Page 89 and 90:
Ozogul, F. and Ozugul, Y., (2000):
Page 91 and 92:
Zeng, Q. Z., Thorarinsdottir K.A.,
Page 93 and 94:
Appendix II: Iron agar (IA) for tot
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