Effect of Chilling on Microbial Load of two Fish Species (Oreochromis niloticus and Clarias lazera)

Abstract

This study was conducted at the Sudan University of Science and Technology, Department of Fisheries and Wildlife Science, to identify the bacterial load on fresh and chilled fresh fish. This study was carried out on 36 fish samples, 18 Tilapia fish (Oreochromis niloticus) and 18 catfish (Clarias lazera), at the period from November 2009 to March 2010. Samples were collected from El-morada fish market and pre-chilled with ice in thermostatic container then, divided into three groups (fresh, iced and refrigerated). The first VIII group was tested fresh, the second was tested after icing from 4 – 7 days and the third tested after refrigerated from 4 – 7 days. The studied samples were tested microbiologically and the results were 8.4×105 and 1.7×105 CFU/gm for fresh Tilapia and fresh catfish respectively. For 4 days iced samples the result was 3.2×105 and 9.3×105 CFU/gm for Tilapia and catfish respectively, for 7 days iced samples the result were 1.7×106 and 1.3×106 CFU/gm for Tilapia and catfish respectively. The result of refrigerated samples for 4 and 7 days were 2.1×106 and 1.1×107 CFU/gm for Tilapia and 8.8×106 and 1.6×107 CFU/gm catfish, respectively. The results of the total bacterial count indicated that the highest contamination steps were the process that tilapia and catfish were packed in polyethylene bags after chilled storage at 4˚c for 7 days, and that Tilapia and catfish showed the level of contamination as 1.1×107 and 1.6×107 cfu\g, respectively. Therefore, total bacterial counts results were over the standard value in TACFS 7001 – 2004 (Thai Agricultural Commodity of Food Standard). While the amount of bacterial count of Tilapia and catfish stored in ice for 7 days were 1.7×106 and 1.6×106 cfu\g, respectively. Also the results showed a significant difference (P < 0.05) between iced and refrigerated samples