Accuracy of Predicting Occurrence of Greening in Tuna Based on Content of Trimethylamine Oxide

Abstract

SUMMARY– To predict green tuna after cooking, a practical measurement to select green tuna using 100 pieces of iced and clipper‐frozen yellowfin tuna was discussed. The most suitable sampling portions, the lowest level of trimethylamine oxide (TMAO) and the total trimethylamine content (TTMA) in tuna muscles were examined. It was recognized that the prediction of green tuna after cooking would be possible by determining TTMA content at the superficial layer of the central dorsal raw muscle (E portion). The lowest level of TMAO‐N was 8–9 mg%, and that of TTMA‐N was 11–12 mg% in an iced and 9 mg% in a clipper‐frozen green tuna. The predictive measurement accuracy was 96% on the lowest level of TMAO‐N or TTMA‐N.

Packaging of retort-processed seafood, meat and poultry

“…Colour changes are more pronounced when the raw material is of poor quality -for example, green discolouration development in canned tuna is attributed to a number of factors, some pertaining to quality status, trimethylamine oxide (TMAO), myoglobin and cysteine concentration and the cooking operation itself (Khayat, 1978). Determination of the combined TMAO and trimethylamine (TMA) content of the raw fish can be used to indicate the probability of greening occurring in the can during the heat process (Yamagata et al ., 1971).…”