Protective Effect of Sinapic Acid on Anthocyanins in Chitosan-Containing Model Beverages

Anthocyanin can be used as a natural colorant in food systems such as beverages, but it is susceptible to degradation by ascorbic acid in foods. Chitosan can be added to beverages for thickening and stabilization, but it can have an effect on the stability of anthocyanin. The effect of different concentrations of chitosan on the stability of anthocyanin in a model beverage system was investigated, and the improvement effect of sinapic acid addition on stability of anthocyanin in the presence of chitosan was analysed. The stability of black rice anthocyanin in different systems was analyzed by accelerated storage experiments and degradation kinetic methods, and the mechanism of action of sinapic acid in improving the stability of black rice anthocyanin in chitosan systems was analyzed by molecular dynamics simulations. The results showed that a single chitosan led to a decrease in the color stability of anthocyanin in the 7 d accelerated experiment. Sinapic acid significantly improved the color stability and content retention of black rice anthocyanin in chitosan-containing model beverages. Degradation kinetic analysis showed that the addition of sinapic acid in the chitosan experimental group at a chitosan mass concentration of 5 mg/mL increased the half-life t_1/2 of the anthocyanin by 2.3 fold and reduced its degradation rate constant K by 0.152 3 d^-1. Molecular dynamics simulation results showed that the presence of free sinapic acid promoted more anthocyanin molecules to approach the chitosan-sinapic acid complex and form a more stable binding. Therefore, the addition of sinapic acid to model beverages containing chitosan could achieve a protective effect on anthocyanins, hoping to provide some theoretical basis for the application of phenolic acid and the optimization of functional chitosan model beverages in the futture.