Protective effect of amino acids on the stability of bayberry anthocyanins and the interaction mechanism between l-methionine and cyanidin-3-O-glycoside

The protective effects of three amino acids ( l -phenylalanine, l -tryptophan and l -methionine) on the stability of bayberry anthocyanins were investigated. The anthocyanin stability under constant illumination (5000 Lux, 50 Hz) or in the presence of ascorbic acid were evaluated by degradation kinetic parameters, and the interaction between l -methionine and cyanidin-3-O-glucoside (C3G) in a model beverage system was analyzed using Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance, X-ray diffraction, molecular docking, and molecular dynamics simulation. Results indicated that the three amino acids significantly reduced the degradation rate of bayberry anthocyanins (p < 0.05), with the most effect by l -methionine. l -methionine could bind to C3G via hydrogen bonds and Van der Waals forces. This study suggested that l -methionine could well protect anthocyanin against degradation in the aqueous solution and have the potential to be used as a co-pigment to improve the sensory property and extend the shelf life of anthocyanin rich berry products.