The Mechanisms of Setting and Modori during Heat-Induced Gelation of Fish Muscle Paste

鱼糜基产品是通过鱼糜中主要蛋白质肌球蛋白的热凝胶化产生的，并通过凝固和变性进行一些改变，称为凝胶变性或弱化。然而，修饰的机制尚未完全阐明。在1995年，我们揭示了从比较研究的设置的青鳕和鲑鱼鱼糜糊，这是代表良好和不良设置的鱼类，设置归因于修改热肌球蛋白凝胶化的内源性转氨酶（TGase）催化的肌球蛋白交联。1996年进行了进一步的研究，以调查在凝固凝胶形成过程中肌球蛋白热凝胶化和TGase催化的凝胶化的组合效应。狭鳕鱼糜的凝胶形成能力因肌球蛋白变性和内源性TGase失活而被完全破坏。在变性鱼糜糊中加入TGase可部分恢复其凝胶成型性。另一方面，在没有TGase活性的天然鱼糜糊中没有诱导凝固。添加TGase还可诱导鲤鱼肌动球蛋白糊的凝固凝胶形成性，这表明了两种不同的Modori机制：（1）当肌球蛋白在最终烹饪前的凝固过程中发生蛋白水解时，凝固时间越长，熟凝胶越弱。(2)当凝胶化先于蛋白水解时，一旦形成的凝胶就退化。SDS-聚丙烯酰胺凝胶电泳（SDS-PAGE）鉴定了肌球蛋白的多聚体及其在TGase催化下交联形成的片段，而加热后的肌动球蛋白结构改变所引起的多聚体尚在研究中。

The surimi-based products are produced through the thermal gelation of myosin as a major protein in the surimi with some modifications by setting and modori known as a degeneration or weakening of gel. Though, the mechanisms of the modifications have not been fully elucidated. In 1995, we revealed from the comparative studies on the setting of walleye pollack and salmon surimi pastes which were representatives for good and poor setting fishes that the setting is attributed to the modification of thermal myosin gelation by an endogenous transglutaminase (TGase) -catalyzed myosin cross-linking. Further studies were undertaken in 1996 to investigate the combined effects of myosin thermal gelation and TGase-catalyzed gelation during the setting gel formation. The gel forming ability of walleye pollack surimi was completely destroyed by the myosin denaturation and inactivation of the endogenous TGase. The addition of TGase into denatured surimi paste partially recovered the setting gel formability. On the other hand, no setting was induced in the native surimi paste without TGase activity. The addition of TGase also induced the setting gel formability into carp actomyosin paste, a non-setting species.Two different mechanisms for modori were demonstrated : (1) when myosin proteolysis occurs during setting prior to final cooking, the longer setting results in weaker cooked gels. (2) when the gelation precedes proteolysis, the gels once formed are degenerated. The polymers of myosin and its fragments formed by TGase-catalyzed cross-linking were identified upon SDS-PAGE.The modori induced by structural alternation of heated actomyosin is still under investigation.