The stability of pelargonidin-based anthocyanins at varying water activity

The stability of pelargonidin 3-glucoside, pelargonidin 3-sophoroside and pelargonidin 3-sophoroside 5-glucoside acylated with malonic and cinnamic acids was determined at varying water activities. Model systems, containing purified anthocyanin in pH 3.4 citrate buffer and glycerol, were stored at 25°C in the dark for 242 days. Changes in pigment, degradation index, and anthocyanin profile, as monitored by high-performance liquid chromatography (HPLC), were studied. In general, anthocyanin degradation followed first order kinetics and the degree of anthocyanin degradation increased with water activity. Half lives of the anthocyanins ranged from 56 to 934 days. Changes in the chromatographic profile showed hydrolysis of pelargonidin 3-sophoroside to pelargonidin 3-glucoside and production of malonic acid from the acylated anthocyanin.