Mechanical and water barrier properties of soy protein isolate film incorporated with gelatin

Soy protein isolate film modified with gelatin was prepared via solvent casting. The effect of gelatin contents on visual, mechanical, water barrier properties and surface hydrophobicity of the films was investigated. It showed that the film containing 30 wt% gelatin had higher tensile strength, elongation at break, contact angle, and lower water vapor transmission rate. Soy protein isolate/gelatin blend film structures were characterized by Fourier transform infrared. Compared with the other films, the 30 wt% gelatin composite film peak intensity is stronger at 1380 cm(-1) and weaker at 1538 cm-1, indicating that the strong hydrogen bonding between - COOH in the soy protein isolate film and -NH2 in the gelatin led to exposing the -CH3 groups in the soy protein isolate film. Scanning electron microscopy showed that the 30 wt% gelatin composite film phase morphology was much finer than the other films. This confirmed that the 30 wt% gelatin soy protein isolate/gelatin composite film has good compatibility. The tests performed showed the potential for gelatin to improve the soy protein isolate film properties. This work provided a new approach to explore such films without plasticizer as biodegradable food packaging.