Optimization Of Enzymatic Hydrolysis For Production And Properties Of Purple Sweet Potato Juice Concentratiom

Purple sweet potato [Ipomoea batatas (L.) Lam.] abundant in natural eatable pigments is a distinctive variety of sweet potato. Since "Chuan Shan Purple" being cultivated in Japan MAFF Kyushu Agriculture Test Site in the early1990s, purple sweet potato has being widely extended in Japan and otherdeveloped countries for it is characteristic of having nutritive components and a variety of medicinal function, such as anti-oxidation, preventing and curing angiocardiopathy, and so on. Preparation and nature of Purple sweet potato concentration juice is discussed. The main results were as follows:Several nutrients of Purple sweet potato were determined:water:60.00g/100g, ash:2.11g/100g,crudefat:0.20g/100g,protein:4.67g/100g,crudefiber:3.31g/100g,starch:29.20g/100g,pigment:0.09g/100g.Purple sweet potato used as raw materials, the technology of biological enzymes were studied in order to produce purple sweet potato juice. By the orthogonal test, the optimum technological parameters of enzymolysis were determined on the basis of single factor experiments, the results showed that, the proper technological parameters of a-amylase were obtained as:water/raw materials=4:1,at the temperature of80℃, pH5.5, a-amylase0.15%, and total hydrolysis time40min; the proper technological parameter of the second processing of enzymolysis were obtained as gluconmylase0.1%, pectolase0.04%, pH4.5, at the temperature of50℃and total hydrolysis time20min.Rheological properties of Purple Sweet Potato concentrated juice were studied at different temperature (25℃,50℃,75℃) and different concentration (100Brix,200rix,300Brix,400Brix,500Brix,600Brix) by the rheometer CV-Ⅲ+.The results showed that within the study of temperature and concentration framework, the Purple Sweet Potato concentrated juice was the Newtonian fluid; Through regression analysis showed that:the effect of temperature on viscosity could be described by Arrhenius type equation, the effect of concentration on viscosity could be described by an Index type equation; and the equation used to describe combined effect of temperature and concentration on viscosity of concentrated Purple Sweet Potato juice was established.