A study was conducted to evaluate meat texture (breaking strength), muscle proximate composition and muscle collagen content at three anatomical locations in cultured yellowtail. We report here the contribution of muscle biochemical constituents to the raw meat texture of cultured yellowtail, and the variation in muscle biochemical composition as well as meat texture with the anatomical location of the meat. Meat breaking strength decreased significantly with the anatomical location of the meat from head to tail. Muscle proximate composition also varied with anatomical location; in particular, a large variation was observed in muscle lipid content, which decreased significantly from head to tail. Muscle collagen content was significantly lower in dorsal part meat than in pre-dorsal part and tail part meat. Meat breaking strength was correlated negatively with muscle lipid content and positively with muscle collagen content. It was concluded that muscle lipid and collagen are the two primary muscle constituents having a direct influence on the raw meat texture of cultured yellowtail. It was also demonstrated that the muscle biochemical composition and raw meat texture of cultured yellowtail vary with the anatomical location of the meat and with season.

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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•

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ABSTRACT:To clarify the contribution of polymerization of myosin heavy chain (MHC) by disulfide bonding to increased gel strength of cooked gel via preheating, the pastes of walleye pollack surimi (SS and C grades) were preheated at 25∞C and 40∞C for a variety of hours prior to heating at 80∞C for 20 min. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) patterns of cooked gels were analyzed with and without reducing the samples, which were solubilized in 8 M urea-2% SDS solution. The formation of polymers by disulfide bonding in cooked gels was almost constant in each of the SS and C grade surimi gels despite the period of preheating. Therefore, it was suggested that polymerization by disulfide bonding occurred during cooking at 80∞C and not during preheating.KEY WORDS: disulfide bond, gel formation, myosin heavy chain, suwari, walleye pollack surimi.

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The digestive conditions were investigated to recover amino acids and peptides from the protein by autolysis from the viewpoint of the effective utilization of the wastes of frigate mackerel. Protein in the head-viscera mixture was efficiently and easily autolyzed at 15•Ž for 24 h at neutral pH. Eighty-seven percent of protein in the mixture were recovered as extractive nitrogen and the autolyt ic extract obtained was rich in free amino acids and peptides. The hot water extract obtained from the autolyzate had umami taste. These results suggested that this autolytic extract can be used as a season ing material.