Abstract: Soybean protein packaging film was prepared from soybean protein isolate (SPI) with a proper amount added plasticizer. However, its practical application was limited primarily by its poor mechanical stability. In this experiment, we prepared SPI films with three different plasticizers: glycerin, sorbitol and oleic acid. Changes in the mechanical properties of SPI films during storage were evaluated by measuring tensile strength, elongation at break, water vapor permeability, and water soluble loss rate. Results showed that the combination of glycerol, sorbitol and oleic acid (2:1:1, m/m) could result in the best mechanical stability of SPI film. Compared with the control group (with glycerin alone), the combination of plasticizers increased the stability of tensile strength, breaking elongation, water vapor permeability, and water soluble loss rate by 64%, 65%, 27%, and 20%, respectively. In conclusion, this study will provide a theoretical basis for extensive application of SPI packaging film.

Key words: plasticizers, soybean protein films, packaging, mechanical properties, stability