1Laboratory of Food Biochemistry, Graduate School of Fisheries Sciences, Hokkaido University, Hakodate 041-8611, 2Central Research Laboratory, Nippon Suisan Kaisha Ltd., Hachioji, Tokyo 192-0906
The inhibitory effect of oxygen gas on the degradation of trimethylamine-N-oxide (TMAO) to dimethylamine (DMA) and formaldehyde in walleye pollack muscle during storage was investigated. At 5°C storage, the formation of DMA in the muscle was markedly inhibited in oxygen gas than in nitrogen gas, air and vacuum. In the case of frozen storage at −5 and −10°C, oxygen gas effectively inhibited DMA formation. At −20°C, oxygen gas also inhibited DMA formation if improved gas supply to muscle tissue was provided. It was found that optimum pH of DMA formation was neutral in walleye pollack muscle during frozen storage at −20°C which was similar to that of TMAOase-like activity mediated by aspolin, but differed greatly from the optimum pH 5.5 in vitro for non-enzymic reaction carried out in a frozen solution containing TMAO, Fe2+ and cysteine.