Effects of Lactococcus lactis (L. lactis) subsp. lactis Supernatant on the Shelf Life of Vacuum-packaged Oncorhynchus mykiss Fillets

The present investigation was done to study the effects of Lactococcus lactis (L. lactis) subsp. lactis on the shelf life of the vacuum-packaged Oncorhynchus mykiss. Fish fillets were prepared and divided into 5 different treatment groups including control (distilled water), 2% and 4% supernatant, and 106 CFU/g L. lactis subspecies lactis. The pH, Thiobarbituric Acid Reactive Substances (TBARS), Total volatile Nitrogen (TVN), and Peroxide Value (PV) of the fillets were determined on days 0, 5, 10, and 15 while maintained at 4˚C. Protein expression and destruction were analyzed using the SDS-PAGE. The organoleptic assessment was done using five expert sensory panelists. Contents of TBARS, TVN, pH, and PV were increased throughout the storage period (P <0.05). An increase in the concentration of supernatant caused a significant decrease in the content of TBARS, TVN, pH, and PV (P <0.05). The highest and lowest contents of TBARS, TVN, pH and PV on 15th day were belonged to the control (3.367±0.04 mg MDA/kg) and pure bacteria (0.70±0.02 mg MDA/kg), control (87.20±6.40 mg/100g) and 4% supernatant (40.79±0.61 mg/100g), pure bacteria (6.23±0.04) and 4% supernatant (5.44±0.07) and control (12.22±0.01 meq/kg) and 4% supernatant (3.08±0.06 meq/kg) groups, respectively. Protein destruction was lower in the fillet samples treated with pure bacteria and 4% supernatant. The highest scores of the odor, flavor, texture, and color were obtained for fillets treated with 4% supernatant, pure bacteria, pure bacteria, and 4% supernatant and pure bacteria, respectively. The results revealed that treating O. mykiss fillets with 4% supernatant and 106 CFU/g of pure L. lactis subsp. lactis can extend the shelf life of O. mykiss fillets.