Study On Nano-SiO_x Soy Protein Isolated Composite Film

The edible film of soy protein isolate (SPI) is a kind of green packaging of food, which is the focal point of modern packing materials of food research. In recent years, nano-materials are the frontier field of materials, and have been applied in the food preservation area because of their special characters. The purpose of this paper was to manufacture composite film using SPI and nano-SiOx. The nano-SiOx surface modification method was studied by orthogonal and response surface experiments (ultrasound modification and compositing modification of surfactant). Then the effects of nano-SiOx on properties of SPI film were investigated. The best technology of composite film was built by investigating the effects of the film on the apple using orthogonal experiment. The microstructure of the film was observed by SEM and AFM.The results showed that the best method of ultrasound modification for nano-SiOx was as follows:pH3,40%of SDS, ultrasonic treating for30min at200W and35℃. The best method of complex modification for nano-SiOx was as follows: pH7,17.5%of SDS, modified for30min at30℃. The ultrasound modified nano-SiOx did not affect the water vapor permeability of SPI film significantly. Adding0.3%of ultrasound modified nano-SiOx, the oxygen permeability and tensile strength of SPI film reached to the highest value, while the water-solubility decreased to the lowest point. Transparency of the film decreased with the increasing of the content of ultrasound modified nano-SiOx. Zero point four percent of complex modified nano-SiOx could enhance the oxygen permeability and tensile strength, and decreased the water vapor permeability and water-solubility of the film. Transparency of the film decreased with the increasing of the content of complex modified nano-SiOx. According to the above results, the complex modification method was superior to ultrasound modification method.The best film technology of composite film was as follows:10%SPI,0.3%nano-SiOx, and soaking for60sec. Under this film conditions, breathing climacteric peak of apple appeared at the fifth week, and the structure of the film was compact and uniform, and the nano-SiOx scattered in SPI film uniformly.