Post-mortem degradation of inosinic acid and related enzyme activity in the dark muscle of fish.

Abstract

In order to elucidate the degradation of inosinic acid (IMP) in the dark muscle of fish, the levels of adenine nucleotides and their related compounds were compared in the white and dark muscles of yellowtail Seriola quinqueradiata and in common mackerel Scomber japonicas during iced storage.The struggling of 30 minutes before death affected the degradation rate of IMP in the dark muscle of yellowtail, while it did not affect in the white muscle. During iced storage, the degradation of IMP proceeded very rapidly in the dark muscle of common mackerel.IMP was degraded optimally at pH 6 and pH 8 in muscle homogenates of common mackerel. The activity in the dark muscle homogenate at pH 6 was 5 times higher than that of the white muscle homogenate, whereas the activity at pH8 was nearly the same in both muscle homogenates. The fact that the high activity at pH 6 was present in the supernatant of the dark muscle homogenate indicated that this enzyme is easily soluble in water. In view of these findings, the fact that the pH of red meat fish such as mackerel falls quickly to around 6 after death suggests that the enzyme activity is mainly responsible for the rapid IMP degradation in the dark muscle. * •‚'m'åŠw"_Šw•

Differences of muscle fiber type and temporal change of K-value among parts toward depth of dorsal muscle in carp (cultured)

“…It was already reported that the IMP degrading activity in dark muscle was higher than that in ordinary muscle. 14,15 From these findings, it was considered that the IMP degrading activity might be higher in the order of red, pink, and white muscle, and the interposition of pink muscle fiber into dorsal ordinary muscle might considerably accelerate the post‐mortem temporal change of K‐value.…”

“… 13 Furthermore, it is known that IMP degrading activity in dark muscle is higher than that in ordinary muscle. 14,15 These findings suggest that IMP degrading activity varies among muscle fiber types of red, pink, and white muscle fibers and then the temporal change of K‐value may also be different.…”

Influence of interposition of pink muscle fiber into dorsal ordinary muscle on increasing rate of K-value in various fish species

“…Recently, in serial studies on muscle fiber types of the dorsal ordinary muscle in fish, Jabarsyah et al 13 have reported that the dorsal ordinary muscle in many fish species is composed of not only white muscle fibers, but also pink muscle fibers arranged in a mosaic pattern. And it is also known that the IMP degrading activity in dark muscle is higher than that in ordinary muscle 14,15 . These findings suggest that the IMP degrading activity may be different among red, pink, and white muscle fibers and also that the interposition of pink muscle fibers into the dorsal ordinary muscle may influence the temporal change of K‐value.…”

Changes in the contents of ATP and its related breakdown compounds in various tissues of oyster during frozen storage

“…It was reported that the post-mortem changes in scallop adductor were closely related to the eating quality of the flesh (Massa et al, 2003). As the rate and pattern of post-mortem changes in nucleotides and their related compounds differ considerably for fish species (Ryder, 1985), muscle types (Obatake et al, 1988), and factors related to handling and storage conditions (Surette et al, 1988), ATP degradation can be used as a good reference. Besides, the chemical assessment of the freshness in post-mortem storage has not yet been well established for bivalves (Suwetja et al, 1989;Yokoyama et al, 1992).…”