Proteolysis and gelation of fish proteins under ohmic heating.

Pacific whiting surimi gels heated slowly in a water bath exhibited poor gel quality, while the ohmically heated gels without holding at 55 degrees C showed more than a twofold increase in shear stress and shear strain over conventionally heated gels. Degradation of myosin and actin was minimized by ohmic heating, resulting in a continuous network structure. Ohmic heating with a rapid heating rate was an effective method for maximizing gel functionality of Pacific whiting surimi without enzyme inhibitors. In linear heating, slow heating rates increased proteolysis in Pacific whiting surimi as shown by degradation of myosin heavy chain and low shear stress and shear strain. Proteolysis of whiting surimi was decreased by the presence of beef plasma protein (BPP) to a greater extent at rapid heating rates (20 and 30 degrees C/min) than at slow heating rates (1 and 5 degrees C/min). Shear stress of Alaska pollock surimi gels with or without BPP increased as heating rate decreased, but shear strain was unaffected. An increase in shear stress was accompanied by an increase of cross-linked myosin heavy chain.