Potential application of lactic acid bacteria for controlling discoloration in tuna (Thunnus orientalis)

Pacific bluefin tuna (Thunnus orientalis) is a highly valued seafood consumed globally. The red color of tuna meat is considered a crucial indicator of its freshness and value, influencing consumer purchasing decisions. Therefore, the present study aimed to investigate the effect of lactic acid bacteria (LAB) isolated from traditional Korean fermented seafood (jeotgal) on preventing the discoloration of tuna meat during storage. Thirty-six strains of LAB (M1–M36) were isolated and examined for superior antioxidant and metmyoglobin conversion activities. Two strains, M1 (Lactococcus lactics) and M8 (Leuconostoc citreum), were selected. Subsequently, the tuna meat was treated with the cell-free supernatant (CFS) of the selected LAB strains and stored at 4 °C. Treatment with CFS maintained a significantly high level of redness (a*) in the tuna meat for up to 48 h; furthermore, this tendency was consistent with the relative quantification of myoglobin derivatives. The oxymyoglobin content in CFS-treated tuna meat remained above 60% for up to 60 h. Conversely, the metmyoglobin content in the untreated group reached over 60% only after 48 h, resulting in complete discoloration. Conclusively, this study demonstrated that LAB-CFS can prevent tuna meat discoloration during refrigerated storage, indicating its potential for maintaining the quality and color of tuna meat. •LAB isolated from jeotgal prevented discoloration of tuna meat.•Two strains showed superior antioxidant activity and metmyoglobin conversion.•LAB cell-free supernatant treatment to maintain redness and to prevent discoloration.