The Study On The Technology Conditions Of Extraction And Purification And Component Analysis Of Anthocyanins Pigment From Purple Sweet Potato

Purple sweet potato (Ipomoea batatas), a new variety of sweet potato, is composed of abundant anthocyanins that make it a potential resource for anthocyanins pigment.The present thesis was focused on the anthocyanins pigment from purple sweet potato cultivated in qingdao, including technology conditions of extraction and purification, stabilities and component analysis.The optimum extraction conditions have been obtained, which included temperature 60C, 0.5% hydrochloric acid, the ratio of sweet potato powder to the extraction reagent 1:25, and extracting time 1 hour for two times. The crude pigment was purified by AB-8 Macro-porous Resin and the adsorption capacity of the resin was determined to be 0.055g/ml resin. After five times used, the adsorbing ability still kept up over 85%. Through the resin purification, the most reducing sugars and starch in the pigment liquid were removed. In this technology, the producing rate of the purple sweet potato pigment reached 7.4% (the color value was 12).The properties and stabilities of the purple sweet potato pigment were conducted. The results showed that the pigment was the water-soluble pigment and presented the steady red in the acid solution. The pigment had better stability to be kept for a long time at low temperature and avoiding light. The stability of the pigment dropped notably in heating or sunlight long-time. Metalions had little influence to this pigment, among them, Al3+ deepened the color, while Fe2+ faded it. Besides, this pigment was sensitive to vitamin C.Three components were isolated thought column chromatography on silica gel. They are identified preliminary on the basis of HPLC, UV, chemical methods and comparison with data in the literatures. Among them, component II and component III were purer anthocyanins, they were peonidin-3- glycoside (diacylated) and peonidin-3, 5- glycoside respectively. Component I was inferred to be flavonoids and comprised complex components.The difference of stabilities were contrasted between component II and component III in different preservation states. The results indicated that the stabilities had relation with the structures of anthocyanins. Component III was superior to component II at the state of sweet potato powders. It is the oxidation mainly to influence the stability. On the other hand, component II was superior to component III in the acid solution. At this moment, it is the acetylation mainly to influence the stability. However, the chromogenic structure of aglycon was not destroyed by acetylation. Therefore, the pigment should be kept in acid solution.