Interaction of Soy Protein Isolate and Meat Protein in a Model Emulsion System. Effect of Emulsification Order and Characteristics of Soy Isolate Used

Abstract

The compatibility of soy proteins with meat protein (MP) in an emulsion system was examined. Three types of soy protein were employed: a commercial soy isolate (CSPI) and two pilot plant samples, an acid treated (ASPI) and a native soy isolate (NSPI). The incorporation of different isolates and the emulsification order affect in a different way the coalescence stability of emulsions prepared with meat proteins. Physicochemical characteristics (surface hydrophobicity, sulfhydryl content, solubility) of the soy proteins cannot explain the different behaviours towards emulsion stability, although the more native sample (NSPI) performed better than the more denature samples (ASPI or CSPI). The addition of NSPI did not modify the high coalescence stability of meat protein emulsion and the effect of the emulsification order was not significant (p 0.05), which suggested compatibility between both proteins. However, the addition of ASPI or CSPI impaired the emulsion stability. When ASPI was emulsified before MP, ASPI inhibited meat protein adsorption and emulsion became highly stable; while when MP was emulsified before or together with ASPI, meat proteins could be displaced from the interfacial film by the ASPI and the emulsion stability was deteriorated. As regards CSPI, all emulsions were highly unstable to coalescence although fractions of both proteins were found in the interfacial film. It could be suggested a mechanism of competitive adsorption when MP is emulsified together with ASPI or CSPI.(