Effect of heat-treatment on some physicochemical properties and emulsifying activity of carp sarcoplasmic protein

Sarcoplasmic protein (Sp-P) from carp Cyprinus carpio was heated at various temperatures from 20 to 100°C for 15 min at pH 7.0, and the physicochemical properties and emulsifying activity of heat-treated Sp-P were investigated. By treatment above 40°C, the solubility of Sp-P decreased and its surface hydrophobicity and reactive SH content increased with a rise in heating temperature. For the soluble fraction of heat-treated Sp-P, the surface hydrophobicity and total SH contents at 50-100°C treatment were somewhat smaller than those at 20-40°C. A 12 kDa component largely remained soluble at 70°C or above and was assumed to be parvalbumin. The emulsifying activity of Sp-P was minimal at 60°C, and thus it was considered to be attributable to heat-coagulable soluble proteins for the lower temperature treatment and to parvalbumin for the higher temperature treatment.