Development of Soybean Protein-Isolate Edible Films Incorporated with Beeswax, Span 20, and Glycerol

The effect of the beeswax, Span 20, and glycerol content on qualities of soybean-protein-isolate edible films was evaluated. Beeswax and Span 20 were selected to improve qualities of soybean-protein-isolate films from 11 emulsifiers. The content of beeswax, Span 20, and glycerol was further optimized by response surface analysis. The optimal composite emulsifier was beeswax (1.87% of soybean protein-isolate), Span 20 (10.25% of soybean protein-isolate), and glycerol (29.12% of soybean protein-isolate) with tensile strength of 908 MPa, percentage elongation at break of 25.8%, water vapor permeability of 19.2 g/m.d.MPa, and oxygen permeability of 0 cm(3)/m.d.MPa. The quality of soybean-protein-isolate films incorporated with the optimal composite emulsifier was 2.34 times higher than that of the control. Furthermore, the disulfide bond content of soybean-protein-isolate films showed a positive correlation with their quality, which provided a simple and rapid way to rank quality of soybean-protein-isolate films. Therefore, our result will not only give an instruction to soybean-protein-isolate-film production, but also give a simple and rapid way to rank film qualities.