Evaluation of tuna meat discoloration by Hunter color difference scale.

Attempts were made to evaluate the discoloration of unfrozen tuna meat, and frozen and thawed (“frozen/thawed”) tuna meat by Hunter tristimulus values (L, a, and b), as a substitute for the metmyoglobin (metMb) ratio (metMb%). Correlation coefficient between metMb% and a/b ratio was higher than that between metMb% and a value. The coefficient was around -0.7 for bluefin and -0.8 ?? -0.9 for yellowfin tuna meat, suggesting that a/b ratio can be used as a parameter to evaluate the discoloration of tuna meat. L and b values were judged not to be useful parameters, since the former was remotely correlated with metMb%, and the latter showed only a small change.