BIOCHEMICAL AND MICROBIOLOGICAL INDICES FOR A KENYA STANDARD FOR FRESH FINFISH

Michael N. I. Lokuruka

Abstract


Currently, the Kenya Standard for fresh finfish includes bacterial limits for 6 species of bacteria, coliforms and the total viable count uppermost limit of consumer acceptability. The standard also provides contaminant limits for toxic metals, but does not give any biochemical indices, and, does not also provide any grades into which fresh fish can be classified at purchase. One of this project’s aim was to study the deterioration profile in ice of 4 major fish species of Kenya (Nile perch, Nile Tilapia, White Snapper and Rabbitfish) in order to establish their shelf life in ice, when gutted and ungutted, and to also establish for each fish species, quality grades based on sensory evaluation and some biochemical and microbiological parameters. The biochemical indices determined included total volatile basic nitrogen, pH, and free fatty acids; in addition, TVC at 22 and 37 oC, coliforms, E. coli, hydrogen sulphide producing bacteria counts at 22 oC were determined for each of four grades of the 4 fish species. Salmonellae and TMAO were not detected in the lake-fish. At rejection point by the taste panel, ungutted beach-purchased Nile Perch, Nile tilapia, White Snapper and Rabbitfish had a shelf life in ice of 25, 25, 29 and 30 days, respectively. FFA was not useful for determination of the quality of farmed, hygienically handled tilapia that was iced properly within 2 hr of harvest. Values of 2.6-2.7 mg FFA/100 g total fatty acids and 25-27 mgN/100 g flesh as TVBN are recommended as maximum limits in a Kenya Standard for fresh finfish. Despite acceptability and wholesomeness of the beach-purchased 4 fish species at the prime and choice grades, the bacterial loads were unacceptably high by food safety standards. The study gives microbiological and biochemical parameters for a potential Kenya Standard for 4 grades of fresh finfish that are useful to the Kenyan fish consumer, retailer and processor aiming to maximize prime quality and value for money

 

Keywords: Nile perch, Nile Tilapia, White snapper, Rabbitfish, grades, Kenya standard


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