Abstract:

The aim of this study was to develop soy protein isolate (SPI) edible films that can be used as food refreshing materials. The SPI edible films modified by different concentrations of glycerol and oleic acid (OA) were prepared. The film-forming dispersions were characterized in terms of the group changes by FT-IR analysis. The appearance, tension strength (TS), water vapor permeability (WVP), optical properties, peroxide value (POV) and contact angle of different films were evaluated. The addition of OA promoted changes in the arrangement of groups on the surfaces of film-forming dispersion (FFD) particles. Microstructure analyses indicated that the OA-treated SPI films had a rougher surface. As regards the film properties, the addition of OA caused a decrease in TS and WVP. The mechanical and optical properties of the films were closely related with their microstructure. In addition, both pH value and temperature had direct effects on the film-forming features of FFD.

Key words: soy protein isolate, oleic acid, glycerol, water vapor permeability, contact angle, opacity, mechanical properties, microstructure