Effect of subzero temperature treatment at −2 °C before thawing on prevention of thaw rigor, biochemical changes and rate of ATP consumption in frozen chub mackerel (Scomber japonicus)

Prevention of thaw rigor in frozen fish with high ATP content is crucial for the quality of the fish supplied for sashimi. In this study, the effect of subzero temperature treatment at −2 °C on the biochemical and quality characters of thawed meat was investigated with an aim to develop a rapid thawing method to prevent thaw rigor in chub mackerel meat frozen in pre-rigor stage. The meat, which was stored at −2 °C in a water bath for 3 h prior to thawing, did not undergo thaw rigor, and both drip loss and hardness decreased. The average ATP consumption rate in the meat with occurrence and non-occurrence of thaw rigor during thawing was 284.0 μmol/(g·h) and 51.6 μmol/(g·h), respectively. The ATP consumption rate during pretreatment at −2 °C was 75.2 μmol/(g·h). Thaw rigor did not occur in chub mackerel when the rate of ATP consumption was below 50–75 μmol/(g·h). These results suggest that this rapid thawing method could serve useful to prevent thaw rigor in pre-rigor-frozen chub mackerel meat.