The effect and evidence of ethanol content on the stability of anthocyanins from purple-fleshed sweet potato

This study aimed to evaluate and understand the water–ethanol system effect on the stability of purple-fleshed sweet potato anthocyanins (PSPa). The stability of the PSPa in the model ethanol–water solutions (0–80%, vol/vol, pH 3.5) during storage (60 hr) at room temperature was monitored by UV-vis. The frontier molecular orbital theory was used to interpret the hydration reaction rate of the PSPa in both ethanol–water and aqueous solutions. In all of the model ethanol–water solutions, the degradation of the PSPa followed first-order kinetics during storage, and the degradation rates increased with increased ethanol concentration. Theory calculation results showed that an increase in ethanol concentration decreased the LUMO energy of anthocyanins, and accelerated nucleophilic attack from water, thus, resulting in lower stability. These findings could provide valuable evidence of the solvent effect on the stability of anthocyanins. Practical applications Fruit wines that contain anthocyanins are among the common alcoholic beverages. The stability of the anthocyanins is responsible for wine quality and may also affect the nutritional properties. Thus, investigating the effect of ethanol on the stability of anthocyanins is particularly valuable. The results of this research have important implications for the models developed so far to explain the degradation mechanism of anthocyanins in different media. In this context, examining the effect of different media on the degradation of anthocyanins would be useful to provide improved anthocyanin ability in the food and beverage industry.