Abstract
Effect of Na-gluconate on physical properties of preheated and two-step heated gel prepared from walleye pollack surimi was investigated in connection with the progress of the cross-linking reaction of myosin heavy chain (HC). The salt-ground surimi to which either 8% sorbitol or Na-gluconate was added, was preheated at 25°C or 40°C. Increases in the breaking strength and the breaking strain, together with the cross-linking reaction of HC, of the salt-ground surimi with Na-gluconate proceeded more slowly than in that with sorbitol during the preheating period. The subsequent heating at 90°C for 30 min enhanced the breaking strength of the preheated gel but slightly decreased the breaking strain irrespective of the type of additive used. Gel stiffness of the two-step heated gels formed with Na-gluconate was higher than that formed with sorbitol at the same breaking strength, suggesting that the two-step heated gels with Na-gluconate were harder but not elastic. This characteristic of the two-step heated gels formed with Na-gluconate was mainly developed due to the subsequent heating. The cross-linking reaction of HC largely proceeded during the preheating period but hardly took place during the subsequent heating period. These results strongly suggest that Na-gluconate contributed to the production of the two-step heated gel with higher gel stiffness by affecting the formation of non-covalent bonds, such as the hydrophobic interaction between myofibrillar proteins.
