Study of quality changes of rainbow trout (Oncorhynchus mykiss) fillet during live-storage in supply tanks

The aim of this study was to compare and evaluate the quality changes of rainbow trout fillets during live-storage in supply tanks. The studied fish included fish kept in a farm and the fish kept alive in supply tanks for 24 h and 72 h. The feeding was stopped 24 h before transportation and during live-storage in supply tanks. The examinations included chemical pH, total volatile nitrogen bases (TVB-N), Free Fatty acids (FFA), peroxide value (PV) and thiobarbituric acid (TBA) and bacterial Pseudomonas spp., psychrophilic bacterial counts, E.coli, Enterobacteriaceae, Total viable count (TVC), colorimetric tests (a*, L* and b*), tissue profile analysis (cohesiveness, gumminess, hardness, elasticity), and sensory evaluation (color, odor, taste, tenderness, appearance, overall acceptability). The pH value ranged from 6.68 to 7.18, which showed a significant increase with increasing the fish live-storage time in supply tanks (P<0.05). The highest levels of TBA, TVB-N, and FFA were measured in fish kept in live supply tanks at 72 h of storage. According to the standards for the amount of bacteria in fish fillets, in the 72h of the storage tanks, only the amount of Pseudomonas was within the permissible range, and in these tanks, other bacteria grew beyond the standard range. The red color of fish fillets or a * was decreased with increasing in the storage time. The fish fillet texture had higher elasticity, hardness and gumminess values with increasing in the live-storage time in supply tanks. Also, the cohesiveness of fillet tissue was increased with increasing in the live-storage time and it was increased from 0.41 N to 0.53 N (P<0.05). The sensory indices of the fish fillets had a significant decreasing trend with increasing in the live-storage time in supply tanks (P<0.05). According to the results, fish live-storage for more than 24 h in supply tanks caused the fillets to deviate from the quality standards in terms of bacterial, chemical and sensory parameters.