Degradation kinetics of rebaudioside A in various buffer solutions

Rebaudioside A is a noncaloric high-intensity sweetener extracted from Stevia rebaudiana. For it to be used in foods, rebaudioside A needs to be stable during processing and storage. This study evaluated the kinetics of rebaudioside A degradation in 0.02 and 0.1m citrate and phosphate buffer solutions at pH 3, 5 and 7 stored at 20, 30 and 40 degrees C for 9months. At pH 3 and temperatures less than 30 degrees C, degradation was slow (i.e. less than 6% loss in 6months) and not affected by buffer type or buffer concentration. At pH 7, the degradation of rebaudioside A increased dramatically in phosphate buffer (losses of up to 25% in 6months at 30 degrees C), while remaining relatively slow in citrate buffer (less than 5% loss). The degradation rates at pH 7 increased 2.6 times as the concentration of phosphate buffer increased. For optimum stability of beverages containing rebaudioside A, formulations with lower concentrations of citrate buffer stored at lower temperatures are recommended.