抄録
When the chub mackerel Scomberjaponicus was kept in icewater, a decline in freshness proceeded accompanying the changes in toughness, pH and K value of muscle. In most specimens full rigor occurred between 2-28h after death, and the resolution of rigor mortis around 20h after death or later. The pH of muscle was between 6.5 and 7.0 immediately after instant death, but rapidly decreased down to 5.7-6.0 during and after full rigor. The K value of muscle did not exceed 5% during pre-rigor but later increased remarkably with the lapse of time.
Chub mackerel specimens of such different degrees of freshness were stored frozen at -30°C for several months. The effect of freshness on the extent of freeze-denaturation of muscle protein was then studied in terms of myofibrillar Ca-ATPase activity. It was observed that there was much more marked denaturation in hte muscle when frozen during post-rigor (pH<6.0, K>5%) than then frozen during pre-rigor.
