Effect of surimi processing on dimethylamine formation in fish meat during frozen storage

Trimethylamine-N-oxide (TMAO) degrades to dimethylamine (DMA) and formaldehyde, which cause a decline in fish quality. Suppression of DMA formation in frozen surimi was investigated using croaker, lizardfish, and walleye pollock. The leaching process in surimi processing was shown to reduce not only the TMAO, iron, and taurine content, but also to reduce unidentified factors that accelerate DMA formation in lizardfish muscle; in contrast, unidentified factors that suppress DMA formation were reduced in croaker and pollock muscle. Sucrose, used as a cryoprotectant, was shown to decrease DMA formation in vitro, likely due to the reduction in freezing-induced concentration of solutes. The effects of pH on DMA formation were different in minced frozen meat among the three species. DMA formation was not observed in croaker when the pH varied between 6 and 8. On the other hand, DMA was elevated in lizardfish under acidic conditions, and DMA formation in pollock was maximal when the pH of the meat was neutral. Thus, the suppression of TMAO degradation by surimi processing results from the removal of TMAO, iron, and reductants from fish meat; sucrose also reduces DMA formation. Furthermore, unidentified factors in croaker, lizardfish, and pollock meat substantially affect DMA formation.