Abstract
The effects of casein on the gelation of walleye pollack surimi paste were investigated. When the surimi paste with or without casein was preincubated (setting) at 25°C for up to 12h, followed by cooking at 90°C for 30min, the addition of casein interfered not only with heat-induced gelation but also setting response.
The addition of 1% and 5% casein to the surimi paste decreased the myosin content by about 9% and 32% on a protein basis, respectively. Since casein did not showa composite reinforcing effect on the surimi gel, the dilution of myosin-myosin interaction may be a major cause of the inferior gelation.
Although myosin heavy chain was a better substrate for transglutaminase (TGase) than casein, casein added into the surimi paste effectively inhibited the enzyme-catalyzed myosin heavychain crosslinking, particularly depressed the formation of its large polymers (n_??_3) during the setting, and resulted in the weakening of cooked gels. A large amount of casein added to actomyosin also inhibited the TGase-catalyzed cross-linking of myosin heavy chain. TGase catalyzed the formation of hybrid proteins from a mixture of actomyosin and casein, but their amounts seemed to be too small to influence the gelling properties of the surimi paste.
