Survey of microbial load and total volatile nitrogen changes in the ice-stored grass carp (Ctenopharyngodon idella)

This study evaluated the total volatile nitrogen (TVN) and microbial load changes (Psychrophilic and mesophilic) as the quality characteristics of grass carp (Ctenopharyngodon idella) that had been preserved in ice for 27 days at times 0, 3, 6, 9, 12, 15, 18, 21, 24 and 27 days. The TVN was measured using autokjeldal method, and microbial load was measured by reference method. The TVN with the initial value of average 20.44 mg/100g showed irregular fluctuation and at the last day of the preservation was higher than standard levels (30.33 mg/100g). The primary Psychrophilic and mesophilic bacterial loads were 2.42 log cfu/g and 2.22 log cfu/g, respectively and increased during the preservation time. Psychrophilic and mesophilic bacterial load reached to 6.47 log cfu/g on day 21 and 6.05 log cfu/g on day 4 respectively. The correlation coefficient of psychrophilic and mesophilic bacterial load with time were 0.972 and 0.960 respectively. In this research, conquering of psychrophilic bacteria and the high growth of them showed that Psychrophilic bacteria have a great role in spoilage of grass carp. Results of this study indicated that TVN is not a good indicator for measuringthe quality of this kind of fish. Also, the shelf life of ice stored grass carp was determined to be 18-21 days.