Effect of Na-gluconate on the physical properties of preheated and two-step heated gel prepared from walleye pollack surimi

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 25degreesC or 40degreesC. Increases in the breaking strength and the breaking strain, together with the cross-linking reaction of HC, of the salt-ground surimi with Nagluconate proceeded more slowly than in that with sorbitol during the preheating period. The subsequent heating at 90degreesC 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.