The Preparation of High Purity of Rebaudioside A and Stevioside and the Enrichment of Rebaudioside C by Subsequent Twice Crystallizations from Natural Stevia Resources

A comprehensive utilization of rebaudioside A (RA), stevioside (ST), and rebaudioside C (RC) from natural stevia resources was proposed. The influence of the solvent, solvent concentration, solid-liquid ratio, temperature, and time on the purity and recovery were investigated with response surface methodology. A 99% purity and 81% recovery of the RA were achieved by one crystallization of crude stevia under optimized conditions. Around a 95% purity and 80% recovery of the ST were easily achieved by the recrystallization of less value of mother liquor sugar (MLS) with a certain concentration of isopropyl alcohol–methanol aqueous solution. During the crystallization of the ST, the enriched RC in the liquid phase was more than three times higher than that in the crude stevia, which can provide cheaper RC raw material for the subsequent preparation of very expensive and high-purity RC.