Effect of genipin crosslinking on the property of chitosan-soy protein isolate film

Genipin (GP) as a natural crosslinker has gained much attention in the food industry on account of its high biocompatibility and safety. In this paper, chitosan (CS)-soy protein isolate (SPI) crosslinked films were prepared using GP as a crosslinking agent. Crosslinking reaction with high contents of GP (0.03%, 0.05%) changed the rheological property of the film matrixes. The crosslinking degree was positively correlated with the content of GP, which was from 21.08 +/- 3.95% of CS-SPI-1 to 39.66 +/- 1.62% of CS-SPI-5. Fourier transform infrared spectroscopy spectra confirmed the crosslinking reaction. The X-ray diffraction and scanning electron microscopy analyses indicated that the crosslinking reaction decreased the crystallinity degree and enhanced the surface roughness of CS-SPI film, respectively. The crosslinking reaction did not significantly affect the thickness, moisture content and water solubility of CS-SPI film. Crosslinked films presented better light barrier capacity. The tensile strength (TS) of CS-SPI-1 was increased by 50%, however, further increasing the contents of GP (0.03%, 0.05%) reduced the TS of the crosslinked films. With the increasing incorporation with GP, the EAB was significantly decreased, while the modulus increased from 95.76 +/- 25.78 to 508.78 +/- 77.95 MPa. The crosslinking reaction improved the rigidity of CS-SPI film. Low crosslinking degree could improve thermal stability of CS-SPI, while higher GP addition (0.03%, 0.05%) decreased the thermal stability and prolonged the degradation time of the film in soil. The results indicated that low crosslinking reaction could improve the property of CS-SPI film, enhancing its potential application in food packaging.