Characterization of Microbiological and Nutritional Variations in Processed Mullet (Mugil cephalus) Fish

The aim of this study was to investigate changes in the microbiological and physiochemical characteristics in Egyptian salted-fermented fish (Feseikh) during processing, ripening and storage. Isolation of total viable bacteria, Enterobacteriaceae, lipolytic bacteria, proteolytic bacteria, total spore forming bacteria (CFU/g) and Clostridium perfringens (MPN) from fish flesh, fish intestine and fish gills was carried out. Determination of moisture, water activity, salt content%, pH values, protein solubility%, protein content%, fat content%, free fatty acid%, peroxide value, thiobarbituric acid value (TBA), total volatile bases nitrogen (TVBN) and trimethylamines, (TMA), fatty acid profile and biogenic amines contents using HPLC was done in fish flesh. The results revealed relatively higher values of total Enterobacteriaceae bacteria isolated from fish intestine (13.13 × 10 CFU/g) than fish flesh and fish gills while total counts of viable bacteria, lipolytic bacteria, 4 proteolytic bacteria and total spore forming bacteria were higher in fish flesh than fish intestine and fish gills. Moreover, Clostridium perfringens was absent in fish flesh. The moisture content after salting decreased from 71.91 to 53.54%.The water activity decreased from 0.9999 to 0.8562% after 60 day. While salt content increased from 0.164 in raw fish to 13.04% after 60 day. Protein content decreased from 18.48 in raw fish flesh to 17.66% after 60 days. Also protein solubility% and fat content% increased from 15.26 and 8.44 in raw fish flesh to 59.29 and 12.84 after 45 days. Free fatty acid (FFA) contents increased gradually throughout ripening and storage. Although peroxide and TBA values provide an indication of onset of lipid oxidation, alternative methods are recommended based on tertiary compounds of lipid oxidation. Total volatile bases nitrogen (TVB-N) increased linearly in fish muscle during ripening and storage. Fish flesh of mullet had the highest fatty acids, that is saturated fatty was more than monounsaturated and polyunsaturated fatty acid. The concentration of biogenic amines was determined in raw fish flesh during processing after 15, 30 45 and 60 days of storage. The results showed that the biogenic amines content of Feseikh fish increased during the long time of ripening and storage.