Abstract: Composite films were prepared from soy protein isolate (SPI) and gelatin by cross-linking with aqueous
glutaraldehyde and saturated glutaraldehyde vapor, respectively. This work comparatively analyzed the effect of different
cross-linking methods on the microstructure, degradability and mechanical properties of films by evaluating the mechanical
properties and degradability of the two composite films. The results showed that during a three-month period of storage, the
tensile strength stability of the composite films processed with aqueous glutaraldehyde and saturated glutaraldehyde vapor
was increased by 20.58% and 38.51%, extensibility stability by 31.71% and 54.49%, water vapor permeability coefficient
stability by 31.74% and 52.19%, and oxygen permeability stability by 0.24% and 18.01%, respectively. The degradation
rates of three different SPI-based composite films were in the decreasing order of native SPI-based composite film > aqueous
glutaraldehyde cross-linking modified SPI film > saturated glutaraldehyde vapor cross-linking modified SPI film. In addition,
the surface and tensile fracture cross-section of the third film were dense and smooth, forming a dense three-dimensional
network structure. Therefore, saturated glutaraldehyde vapor cross-linking was a better method to modify SPI-gelatin
composite film than aqueous glutaraldehyde cross-linking in terms of mechanical property stability and microstructure.

Key words: glutaraldehyde vapor cross-linking, aqueous solution cross-linking, SPI-based gelatin composite film, stability, degradability, microstructure