Effect of long-term storage, ultra-low temperature, and freshness on the quality characteristics of frozen tuna meat

This study clarified the validity of conventional frozen storage temperature of tuna meat, and investigated the effects of long-term storage and ultra-low temperatures, as well as the effect of the freshness at the time of freezing on the quality of tuna meat. Samples were grouped according to their pH: Low-pH (pH < 6.2) and High-pH (pH > 6.8). The increase in metMb% was higher in the Low-pH samples stored at temperatures higher than −40 °C. An increase in the metMb% was not observed in meat stored at −45 °C or lower, irrespective of the pH. The changes in the drip loss, the microstructure, and sensory scores in the High-pH samples were smaller than those in the Low-pH samples throughout frozen storage. The results demonstrated that the slight differences in freshness affected the quality of tuna meat during frozen and subsequent chilled storage.