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The effect of genipin (GP) concentrations on the structural, mechanical, and water barrier properties of chitosan (CS)/rice protein hydrolysate (RH) composite films was investigated for further incorporating of curcumin. GP increased the stability of CS/RH conjugate in solution. The degree of CS/RH crosslinking depended on genipin concentration, as indicated in particle size and UV spectra. At optimal genipin concentration (0.4 mg GP/g total biopolymers), the CS/RH film had the lowest moisture content (10.67%) and water vapor transmission rate (829.35 g/m2·24 h.). Genipin could enhance the tensile strength and thermal stability of the CS/RH films depending on GP addition concentration. With an increased amount of GP, the DPPH scavenging activity decreased due to the cross-linking of antioxidant peptides, and the E* value increased indicating the significant color differences caused by increasing GP. Notably, the addition of curcumin had a positive effect on the DPPH scavenging activity and antimicrobial activity of the CS/RH films. Curcumin-loaded CS/RH films had higher antibacterial activity against S. aureus than E. coli. In general, the suitable addition content of GP was a promising and green strategy to improve the properties of the CS/RH films. [ABSTRACT FROM AUTHOR]

Self-assembly and molecular spectroscopy are widely used in protein research. However, studies underreported the interaction of rice glutelin (RG) and egg white protein (EWP) under pH-cycle treatments, which had differences between initial and final environment. Herein, the possible interaction mechanism of RG-EWP self-assembly behavior was demonstrated by spectroscopy or other characterization methods under different conditions and proportions. Fourier transform infrared, circular dichroism, intrinsic fluorescence, and UV absorption spectroscopic methods showed changes in the secondary and tertiary structures of RG or RG-EWP. Results also revealed the degree of protein folding and exposure status of aromatic amino acid residues. The nonignorable surface hydrophobic and electrostatic interactions were observed by ζ-potentials and surface hydrophobicity. The electrophoretic analysis showed increased 48 kDa subunits. The high solubility (over 92%) of RG-EWP was discovered as potential functionality at total ratio of 90% and 50% RG. This study improved the asymmetric pH-cycle theoretical mechanism and widened RG-EWP application.Graphical Abstract: Self-assembly and molecular spectroscopy are widely used in protein research. However, studies underreported the interaction of rice glutelin (RG) and egg white protein (EWP) under pH-cycle treatments, which had differences between initial and final environment. Herein, the possible interaction mechanism of RG-EWP self-assembly behavior was demonstrated by spectroscopy or other characterization methods under different conditions and proportions. Fourier transform infrared, circular dichroism, intrinsic fluorescence, and UV absorption spectroscopic methods showed changes in the secondary and tertiary structures of RG or RG-EWP. Results also revealed the degree of protein folding and exposure status of aromatic amino acid residues. The nonignorable surface hydrophobic and electrostatic interactions were observed by ζ-potentials and surface hydrophobicity. The electrophoretic analysis showed increased 48 kDa subunits. The high solubility (over 92%) of RG-EWP was discovered as potential functionality at total ratio of 90% and 50% RG. This study improved the asymmetric pH-cycle theoretical mechanism and widened RG-EWP application. [ABSTRACT FROM AUTHOR]