The crude extracts was mixed with 37.5 ml chitosan solution and incubated at room temperature for 20 min. Chitosan solution was prepared by dissolving 1 g of chitosan in 100 ml of 1/5 acetic acid. As a cationic polysaccharide, chitosan has the ability to chelate with protein and tannic acid in the mogrosides extract by the active interface made by chitosan's functional groups such as hydroxyl and amine groups.