Development and characterization of sodium caseinate edible films cross-linked with genipin

Edible films were prepared by cross-linking sodium caseinate (NaCas) with genipin (GP) at the levels of 0.2, 0.4, 0.6, 0.8, 1.0 or 1.5 mg GP/g NaCas to improve the physiochemical properties of NaCas films. The thickness and moisture content of NaCas films were not significantly (p >= 0.05) affected by GP levels used. As compared with the NaCas films prepared without GP, significantly (p < 0.05) lower water vapor permeability was observed starting from the GP level of 0.4 mg/g NaCas. The color attributes were influenced by the amount of GP used in film preparation. As the amount of GP increased, L*, a*, b* and whiteness index of NaCas films gradually decreased. Most importantly, the tensile strength and Young's modulus of the NaCas films increased and the break elongation of films decreased as the amount of GP increased. Furthermore, FTIR spectra confirmed the cross-linking reaction between GP and NaCas. Collectively, the incorporation of GP as the cross-linker has a great potential to improve the physicochemical properties of edible NaCas films.