Below-zero storage of fish to suppress loss of freshness
The decomposition of ATP in flounder and greenling muscle were compared at 0 and − 2 °C. The decomposition of inosine-5-monophosphate (IMP) and subsequent increase in the K-value were suppressed at − 2 °C for both species, although the K-value increased much more slowly for flounder than for greenling. When flounder was stored at 0 °C, a high IMP content was maintained for more than 10 days, and then dropped quickly. This quick reduction in the IMP content was not observed at − 2 °C. The fast reduction in the IMP content at 0 °C was explained by the activity of an IMP-decomposing enzyme produced by spoilage microorganisms; it no longer occurred when the meat was stored in the presence of 150 p.p.m. of the antibiotic chloramphenicol. 5′-Nucleotidase produced by the bacteria was less stable than that produced endogenously. Spoilage bacteria also produced a strong protease that degraded muscle protein. It was concluded that lowering the storage temperature of flounder and greenling from 0 to − 2 °C suppressed the growth of spoilage bacteria and slowed the increase in the K-value.
KeywordsInosine-5-monophosphate K-value 5′-Nucleotidase Super-chilling Decomposition
This research was supported by grants from the NARO Bio-oriented Technology Research Advancement Institution (the special scheme project on a regional development strategy).