English abstract
The present study was undertaken to assess the effects of storage conditions on the shelf life by comparing the sensory, microbiological and chemical quality attributes of yellowfin tuna (Thunnus albacares) caught in the Omani coastal waters. Using healthy muscle tissue, bacteriological changes, histamine formation and K values were determined for fish stored at temperatures of 0, 8, and 20°С. Sensory analysis was conducted on a whole yellowfin tuna (YFT) using a semi-trained panel that consisted of eight to ten assessors all of which had a food science background.
Results of the study showed that temperature is a critical variable for the quality and safety of fish. Storage at 0°C greatly extended the shelf-life of yellow fin tuna as compared to 8°C and 20°С. Freshness of YFT was assessed by K-value determination. Fish maintained its freshness up to 17 days, 6 days and 24 hours at 0°C, 8°C and 20°C, respectively.
Histamine levels declined during storage at 0°C with values within the acceptable levels specified by FDA (5 mg 100 g) and the European Union (10 mg 100 g:). This was in contrast to 8°C and 20°C where unacceptable levels were reached after 4 days and less than 24 hrs, respectively.
A rapid increase in the amount of histamine produced was observed when fish were stored at 8°C or 20°C. This correlated with an increase in the proportion of mesophilic bacteria when compared to 0°C.
Sensory evaluation was shown to be an effective method as bacteriological and chemical parameters were still within the acceptance limits when the fish became unacceptable in sensory terms.
