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Complementary DNA encoding a part of myosin heavy chain was cloned from fast skeletal muscle of Japanese codling Physiculus japonicus. Japanese codling, a frequent catch off the Pacific coast of northeastern Japan, is a typical underutilized fish species, especially in summer. Phylogenetic analysis of the deduced amino acid sequence of Japanese codling myosin heavy chain loop 2 region revealed that this fish belongs to a group comprising white croaker Pennahia argentata and walleye pollack Gadus chalcogrammus, which are commonly used as raw materials for surimi-based products. Thus Japanese codling meat was considered a promising candidate ingredient for surimi-based products. Salt-ground meat was prepared from Japanese codling in the presence of 0.5 M NaCl and subjected to a two-step heating procedure: pre-heating at 15–70 °C for 30 min, and secondary heating at 85 °C for 20 min. Thermal gels with a maximum breaking strength of > 10 N were produced by this process. The breaking strength was comparable to that of white croaker and walleye pollack. On the basis of the phylogenetic analysis of myosin heavy chains, and the properties of the heat-induced surimi gel, we conclude that Japanese codling is a promising raw material for the production of surimi-based products. [ABSTRACT FROM AUTHOR]

ABSTRACT: Chub mackerel (34–35 cm, approximately 500 g), which were caught by fishing with a rod and line at the Bungo Channel, Oita prefecture, were rested overnight in a fish preserve and either killed by decapitation (control group) or allowed to struggle in air for 30 min (struggled group). Muscle samples were excised every 4 h, and measurements on breaking strength and histological observations were done for both groups. The breaking strength of muscle in the control group was significantly higher than that in the struggled group, whereby a decrease in breaking strength was delayed for 12 h compared to the struggled group. Light microscopy showed space extension among muscle cells in association with a decrease in breaking strength. Especially in the struggled group, the extended area was larger and the difference in area was significant at the time when breaking strength showed a significant difference. Using electron microscopy, the extended area showed cut and/or disappeared collagen fibrils. From these results, it was demonstrated that struggling to death promoted the degradation of collagen fibrils and the weakening of connective tissue and, resultantly, led to the faster softening of muscle of chub mackerel. [ABSTRACT FROM AUTHOR]