A number of studies have been reported on the change in the acid-soluble nucleotide of muscle tissue. In fish muscle, however, few works have been done on the relation between the change in the nucleotides and the freshness based on the bacterial spoilage. It is proposed recently from a consumer's standpoint that the flavor quality index of muscle tissue is more desirable as the freshness rather than the bacterial spoilage index. The present paper deals with the relationship between the change in the concentrations of various nucleotides, VBN and the number of bacteria in carp muscle during the chill-storage.
The concentration of IMP is quite important as the index of flavor quality of fish muscle, because IMP is the major nucleotide in fish flesh as the flavor-enhancing constituent. The amount of IMP reached the maximum level (5.5 μ mole/g) at 0-4°C one day after slaughter of carp. IMP stays about three days without appreciable change under this chill-condition. Following 4-day storage, however, IMP was decreased rather rapidly. On the other hand, the bacterial spoilage was found to occur after 11-day storage. Therefore, the maintenance time of IMP, namely, the time of keeping passable flavor quality of carp muscle was one third to one half of the time of incipient spoilage.