Studies On Mulberry Red Pigments: Extraction, Isolation And Structure Identification

In this thesis, the methods of extracting and isolating anthocyanins from mulberry wastes are studied, as well as the main structure and properties of it. The results are as follows:1. Measurement of total anthocyanins in mulberry by UV-visible spectroscopy is dependant on the solvent system adopted. Compared in the solvents with the same concentration, both direct method and pH-differential method are within the linear range of the spectropHotometer, and the direct method is much more convenient but of the same veracity. However, in the solvents of different concentration, the pH-differential method is much more accurate and is recommended.2. Three methods of extracting red pigments from mulberry are optimized and compared. Under the optimized conditions of 30% ethanol, material ratio of 1:10, extracting 30 min at 40℃, the ultrasonic assistant method gained the highest amount of pigments, that is 3.906mg/g. Others are the traditional method and the enzyme assistant method, with productivity of 1.571mg/g and 0.499mg/g respectively.3. Five kinds of macro-reticular resin such as resin AB-8, D-4020, D-101, X-5 and X-6 are studied. AB-8 is the best resin of all. Static and dynamic experiments are optimized with resin AB-8 to produce mulberry pigments. The optimum conditions of adsorption were: material concentration of 40% , pH 2.0, and adsorption rate at 4.5 ml/min;while the optimum conditions of desorption were: material concentration of 50% , pH1.5, and adsorption rate at 1.5 ml/min4. Four kinds of ion-exchange resin such as resin D152, D151, 001-7 and D001 are studied. D151 is the best resin of all. Static and dynamic experiments are optimized with resin D151 to produce mulberry pigments. The optimum conditions of adsorption were: material concentration of 40% , pH 2.0, and adsorption rate at 1.5 ml/min;while the optimum conditions of desorption were: material concentration of 50% , pH2.0, and adsorption rate at 1.5 ml/min5. Both of the two resin methods could totally remove galactose in mulberry red pigments, and had distinctive purification effects on glucose and fructose. However, ion-exchange resin D151 did better purification work against sugar than macro-reticular resin AB-8 did.6. Paper chromatography was used to resolve the main anthocyanin structure in mulberry pigments, that is cyanidin-3-glucoside. UV spectroscopy and partial hydrolysis analysis were then used to identify the initial deduction.7. Mulberry red pigments showed strong deoxidizing ability. In addition, under low concentration (0.02%) and high concentration (1%, 5%), the pigments restrained the lard oxidization. In the experimental conditions, the more the pigments are purified, the lower the antioxidation ability they have.