Study on Emulsifying Properties of Mixture System for Tilapia Protein and Soybean Protein

[Objective] Emulsifying properties of mixture system for plant protein and animal protein were determined. [Method]Fish protein isolates( FPI) and soy protein isolates( SPI) were prepared by alkaline solution and isoelectic precipitation from Tilapia muslce and defatted soy flour produc. Effect of pH value,NaCl concentration and polysaccharide on the emulsifying ability and emulsifying stability was studied for mixing system at 0. 5% of protein concentration. [Result]In the pH value range from 3. 0 to 10. 0,for FPI,FPI-SPI( 2∶ 1),FPI-SPI( 1∶ 1) and SPI system,the same trend was obtained for emulsifying properties with increased pH value. The minimum emulsifying activity and stability values were obtained at pH 4. 0-5. 0,while the larger values were observed at pH 3. 0 and 10. 0. At pH 3. 0,emulsifying activity of mixing protein system decreased with addition of NaCl( range from 0 to 0. 4 mol/L),while emulsifying activity increased with NaCl addition at pH 5. 0 and 7. 0. The addition of xanthan gum,carrageenan,guar gum and chitosan could improve emulsifying properties of mixed protein system. In comparison,effect of guar gum on emulsifying activity of mixture system was most obvious,effect of xanthan gum on emulsifying ability was most remarkable,and no obvious improvement was observed for adding chitosan. [Conclusion] Effect of physical mixing of two proteins on the emulsifying properties was limited,and the addition of polysaccharides can improve effectively the emulsifying properties.