Freeze Denaturation of Myofibrillar protein from Unstable Winter Silver carp (Hypophthalmichthys molitrix) and its Suppression by Sucrose

抄録

Freeze denaturation of myofibrillar protein prepared from winter silver carp and its suppression by sucrose when frozen as mince and washed mince was investigated. The ATPase activity and salt-solubility of myofibrillar protein were measured as the indices of myosin denaturation. Sucrose at 8% was used as cryoprotectant. All samples (with and without sucrose) were frozen at different freezing -rates (1, 0.1, 0.01°C/min) and then stored at -40°C, -20°C, and -10°C for one month. Ca²⁺-ATPase activity decreased to near 50% just by freezing for the washed mince, while the remaining activity for minced meat was about 80%. Addition of sucrose suppressed the Ca²⁺-ATPase inactivation by freezing and kept near 100% activity regardless of the freezing rate. Myosin denaturation was determined by the frozen storage temperature, showing high remaining activity for the samples stored at lower temperature (-40°C). However, decrease in Ca²⁺-, Mg²⁺-ATPase activity and salt-solubility upon frozen storage was almost completely suppressed by adding 8% sucrose, even if the storage temperature was -10°C. These results indicated that sucrose at 8% was sufficiently high for protecting myosin denaturation. It is also suggested that the utilization of surimi is promising for the unstable winter silver carp.