Physical interaction between gallic acid and Monascus pigments enhances mechanical strength and pigment protection of pectin-gelatin hydrogel carriers

Natural polymer hydrogels formed by polysaccharides and proteins can be protective carriers for Monascus pigment (MPs) in the food industry. In this study, in order to enhance the mechanical properties of the hydrogel and its ability to protect MPs, we introduced polyphenols as bifunctional components into the hydrogel carrier. This hydrogel carrier consisted of gallic acid (GA) grafted pectin (LPG) and gelatin. The results showed that the grafting of GA enhanced the affinity between MPs and pectin. A more compact network structure formed by pectin under the interaction of MPs with GA improved the mechanical properties of the hydrogel carriers. With the combination of GA with MPs, the gelation rate of the hydrogel carrier was accelerated, the gel strength increased from 550.07 g to 937.67 g and its water swelling rate decreased significantly from 447.87 % to 311.76 %. Moreover, the multiple pigment protection produced by the GA in the hydrogel greatly reduced the degradation rate of MPs under continuous light expose conditions. The findings provide new insights into developing hydrogel carriers for pigment protection with ideal mechanical properties.