Preparation of Soy Protein Isolate (SPI)-Pectin Complex Film Containing Cinnamon Oil and Its Effects on Microbial Growth of Dehydrated Soybean Curd (Dry Tofu)

Abstract

The effects of cinnamon oil and ratio of soy protein isolate (SPI) to pectin on tensile and microstructure properties of complex edible film were investigated. When the ratio of SPI to pectin solution was 5:1, the mechanical properties were improved according to the interaction of protein and polysaccharide through electrostatic forces. The addition of cinnamon oil that led to an increase or decrease in the tensile strength depends on its concentration, but decrease in the deformation at break within the concentration range. SPI-pectin complex film containing cinnamon oil had antimicrobial activity especially to fungal microflora. Gompertz-derived kinetic parameters for microbial growth of dry tofu packaged with or without SPI-pectin complex film were obtained. It was found that the SPI-pectin complex film can inhibit the growth of microbial flora in dry tofu and might be used as a package for extending the shelf life of dry tofu. Practical Applications This research would have practical applications in food package. The mechanical properties of soy protein isolate (SPI) film were improved by addition of pectin. The SPI-pectin complex film containing cinnamon oil can inhibit the growth of microbial flora especially to fungal microflora in dry tofu.