Effects of freezing on chemical and microbial features of edible tissue of John's snapper (Lutjanus johnii)

This research aims to investigate the effects of freezing and frozen storage at -18°C on the chemical and microbial features of edible tissue of Lutjanus johnii. 30 samples of fish with average weight and length of 708 g and 35 cm were obtained from the fish market of Bushehr seaport in 2015 and were stored for 180 days in a freezer. The results of this research indicated that the amounts of crude protein, crude fat, ash and moisture of fresh samples were 15.87, 4.50, 2.37, and 77.72% respectively, whereas these amounts were changed to 15.57, 4.02, 3.00 and 77.12% respectively after 180 days of frozen storage. The amounts of pH, total volatile nitrogen and peroxide of fresh samples were 5.59, 14.36 mg N2/100g and 0.77 meq O2/kg respectively, whereas these amounts were changed to 6.85, 19.63 mg N2/100g and 1.97 meq O2/kg respectively after 180 days of frozen storage. Microbial analysis showed that total bacterial count in fresh sample was 3.00 log CFU/g that was changed to 3.47 log CFU/g after 180 days of frozen storage. According to these results and by comparing the results with the standards, it can be concluded that the nutritional value of this fish was not noticeably decreased after 180 days of frozen storage.