Effect of catechin and tannins on the structural and functional properties of sodium alginate/gelatin/ poly(vinylalcohol) blend films

The catechin and tannins as crosslinking and antioxidant compounds were added into sodium alginate/gelatin/poly(vinyl alcohol) (SA/GEL/PVA) blend film with 0.5%, 2%, and 5% (based on the total mass of polymers), respectively. This study aims to investigate the effect of different polyphenols on the structural and functional properties of food packaging film. Molecular interactions among polyphenols and polymers in film-forming solution (FFS) were analyzed based on the rheological behavior, low field nuclear magnetic resonance (LF-NMR), and the changes in structural characteristic of modified films were analyzed through Fourier transform infrared spectra (FTIR), Scanning electron mcroscopy (SEM) and X-ray diffraction (XRD) analysis. The results indicated that the crosslinking degree of the polymer network in FFSs modified by tannins was higher than that of catechin. The mechanical properties, water insolubility, water vapor barrier performance and antioxidant activity of the blend film were improved by polyphenols addition. The film modified by 2% tannins showed the highest tensile strength and elongation at break in comparing with catechin modified films. This study demonstrated that the tannins have a great potentiality in enhancing the structure and function of SA/GEL/PVA blend film.