Pacific Whiting 冷凍すり身のゲル化に伴って起こる筋原繊維タンパク質の変化と牛血漿粉末添加の効果

A study was made to clarify the polymerization and degradation profile of myofibrillar proteins in the salt-ground meats during heat-induced gelation process of Pacific whiting frozen surimi and the effects of bovine plasma protein on it.

Frozen surimi was thawed and ground with 2.5% NaCl in the presence and absence of bovine plasma powder (0.5～10.0%). The salt-ground meats preheated at a fixed temperature in the range of 20 to 60℃ for 2～34 hours were subjected to subsequent heating at 90℃ for 20 minutes. The subunit composition of myofibrillar proteins in the gels was analyzed using SDS-polyacrylamide gel electrophoresis. When the salt-ground meats were preheated at 30～40℃, myosin heavy chain (HC) in the gels slightly decreased with the production of its polymer, while at 50℃ and over, HC was degraded to the unidentified components with lower molecular weight, namely X[1] and X[2], which were postulated to be limited degradation products of HC. The subsequent heating at 90℃ markedly increased the production of X[1] and X[2] with the decrease in HC and its polymer in the preheated gel. Bovine plasma powder suppressed the polymerization and degradation of HC during the heating process of salt-ground meats, and the suppressive effects was concentration dependent of the plasma powder added.

Considering the gelation profile of the Pacific whiting frozen surimi introduced in our previous paper (Kato et. al., 2003), bovine plasma protein was presumed to reinforce the gelation of myofibrillar proteins in the salt-ground meat through the inhibition of the production of the X[1] and X[2] from HC as well as the heat-induced gelation of bovine plasma protein itself at higher temperature.

Pacific whiting 冷凍すり身の熱ゲル化に際して, 塩ずり身中のタンパク質に起こる変化と, それに対する牛血漿タンパク質の添加の効果について検討を行った.

冷凍すり身を解凍後, 2.5% NaClまたは2.5% NaClと0.5～10.0%牛血漿粉末を加えて塩ずりし, 塩ずり肉を20～60℃の間の一定温で2～34時間予備加熱後, 90℃で20分本加熱した. 調製された加熱ゲル中の筋原繊維タンパク質組成をSDSPAGE法によって分析した.

30～40℃で加熱するときミオシン重鎖(HC)は減少して僅かにその多量体を生成するが, 50℃以上ではHC の部分分解産物に相当するX[1]とX[2]成分を生成した. また90℃, 20分の加熱ではHC 及びHC 多量体が消失して多量のX[1]及びX[2]成分を生成した. 牛血漿粉末を添加すると, このようなタンパク質組成の変化は添加量に依存して抑制された.

これらの結果と先に報じた塩ずり身のゲル化特性の関係から, 牛血漿タンパク質は, HCのX[1]とX[2]への分解抑制を介して, 塩ずり肉中の筋原繊維タンパク質のゲル化と, 高温における牛血漿タンパク質自体の熱ゲル化とを併せて増強すると考えられた.