Assessment of Commercial Quality Evaluation of Yellowfin Tuna Thunnus albacares Meat Based on Myoglobin Properties

Four quality grades (excellent, good, acceptable, and "not acceptable") of yellowfin tuna meat (Thunnus albacares), as judged by a professional appraiser, were compared based on the red/ox state and extractability of myoglobin (Mb). As a result, the metMb ratio of the "not acceptable" grade of meat was significantly higher than that of the other higher-grade samples. In contrast, the highest ratio of oxyMb was found in the "excellent" meat, followed by good > acceptable > "not acceptable" meats. Color measurement revealed significant differences in a* value between the different grades of meat, but showed essentially no difference in L* and b* values. Both a* value and redness index (a*/b*) showed high correlation coefficients with metMb ratio. Mb extractability tended to be higher in the higher grade of meat. In conclusion, the commercial appraisal of tuna meat quality was demonstrated to be reliable.