Separation And Purification Of Anthocyanins From Mulberry Fruit

Mulberry (morus alba) has been domesticated over thousands of years and adapted to a wide area of tropical, subtropical and temperate zones of Asia, Europe, Africa, North and South America. Recently, many researches have shown that mulberry fruits had antioxidant polyphenols, mainly anthocyanins, flavonols, flavonol glycosides and phenolic acids. Additionally, several researchers previously reported that red and black mulberries contained anthocyanins, which have remarkable antioxidant and free-radical scavenging activities.The aim of this study was to evaluate the solid wastes from mulberry juice industry through their contents in polyphenolic and in vitro antioxidant activities. Furthermore, apple pomace and grape pomace, which had been applied widely in natural antioxidants manufacture, were also considered in order to carry out a comparative assessment. The results showed that mulberry pomace had the highest total polyphenols (2810 mg per 100 g dry weight) and outstanding antioxidant activities, which were 1.9-4.0 times higher than those of apple pomace. The antioxidant activities were not significantly correlated with the level of polyphenols, suggesting dependence on particular structural features. The results indicated that mulberry pomace had outstanding antioxidant activities and might be used as a potential source of natural antioxidant agents.The effect of different drying methods and conditions on polyphenolic content and antioxidant properties of mulberry fruit during food processing treatments was investigated. The present work was aimed at studying the effect of four drying methods (freeze-, microwave-, vacuum-, and air-drying) and air-drying temperatures used (from 30 to 90℃) on total phenolics content (TPC), total flavonoids content (TFd), total anthocyanins content (TMA) and antioxidant properties of mulberry fruit. The results showed that there were significant differences amongst all the treatments. Among the drying methods, effectiveness was in a descending order of freeze-> air->microwave->vacuum-drying. In view of economic and effect, air-drying is more suitable for industrial practices. Meanwhile, air-dried fruit at 90℃showed higher polyphenolic content and antioxidant properties than those at low temperatures (30,50 and 70℃). It could be demonstrated that air-drying at 90℃can produce high-quality products, with the additional advantage of reduced processing time and low cost.The condition for isolation of anthocyanins from mulberry has been evaluated and optimized. The optimum conditions for anthocyanins are as follows:solvent is ethanol-water (91.03:8.97, v/v), extraction 1 times, hydrochloric acid concentration is 0.5%, extracting time is 31.33 min, the ratio of solvent to solid is 19.47:1 (ml/g), and extracting temperature is 50℃, the maximum yield of anthocyanins is 2.19293mg/g and the maximum yield of anthocyanins is 2.91972%.The adsorption and desorption properties of anthocyanins on 19 different macroporous resins were compared. HPD100 resin offered the best adsorption and desorption capacities based on the research results. Dynamic adsorption and desorption experiments on HPD100 resin packed column were conducted and the optimum parameters for adsorption were as follows: flow rate is 3BV/h, feed concentration is 0.8mg/ml; for desorption:eluent is 2BV/h ethanol-water (40:60, v/v).flow rate is 7BV/h. After the treatment with step wise elution on HPD100 resin, the content of anthocyanins in the product increased from 2.92% to 38.91% which is 12.3-fold higher than it in mulberry fruit, while the color value of anthocyanins in the product increased from 7.84to 128 which is 15.3-fold higher than it in mulberry fruit. The recovery yield was 76.3%.