Separation,purification And Stability Of Anthocyanins From Blueberry Peel Residue

Blueberries are rich in anthocyanins.During the deep processing,a large amount of anthocyanins will still be retained in the peel residue.In order to maximize the utilization value of blueberries and realize the reuse of waste,this study took the blueberry peel residue,a by-product produced by beverage factories,as the raw material to explore the best experimental conditions for extracting anthocyanins.Then the crude extract of anthocyanin was further purified by aqueous two-phase system and macroporous resin,and a more suitable method for industrialization was selected through comparison.The stability of the final purified product under different conditions was studied.The main findings were as follows:In the extraction experiment of blueberry anthocyanins,it was found that the concentration of anthocyanins extracted with 60%ethanol aqueous solution was the highest,with relatively few impurities and high clarification of the extraction solution.The concentration of anthocyanins extracted at 30℃and room temperature was basically the same.Considering the cost,60%ethanol aqueous solution was finally selected at room temperature for 6 h for extraction,with a solid-liquid ratio of 1:5 and secondary extraction.In the experiment of purification of blueberry anthocyanins by aqueous two-phase system,two aqueous two-phase systems were selected for single factor and orthogonal experiments.The ethanol/ammonium sulfate system was optimized as ammonium sulfate of 22.5%,ethanol of 24%,p H 4.5,and pigment addition of 15%,under which the selectivity coefficientβwas 27.10.The ethanol/sodium dihydrogen phosphate system was optimized as sodium dihydrogen phosphate of 25%,ethanol of 29%,p H 2.5,pigment addition of 14%,under which the selectivity coefficientβwas 140.05,which was 5 times the selectivity coefficient of the ethanol/ammonium sulfate system,indicating that the ethanol/sodium dihydrogen phosphate system was more conducive to the purification of blueberry anthocyanins than the ethanol/ammonium sulfate system.However,additional inorganic salts were introduced into anthocyanin products treated by the aqueous two-phase method,resulting in a low color value of 3.94.The color value of the product could not meet the commoditization requirements and required further purification.However,further purification could lead to complex production steps,which was not conducive to industrial production.In the experiment of purification of blueberry anthocyanins by macroporous resin,DM-21,SP-207 and LS-305 resins were selected from X-5,AB-8,XAD-16,XAD-7HP,DM-21,SP-207 and LS-305 resins with their higher static adsorption capacity and desorption ratio.The static adsorption data of the three resins were more consistent with the Langmuir equation,and the adsorption was more inclined to monolayer adsorption.According to the Q_max at p H 3.0,the resins were ranked as LS-305>SP-207>DM-21,and the adsorption kinetics was more inclined to the pseudosecond-order kinetics model.Further dynamic experimental screening of these three resins showed that both LS-305 and SP-207resins had good adsorption and desorption capabilities for blueberry anthocyanins.Considering the high price of SP-207 resin,LS-305 resin was selected for subsequent experiments.The color value of the blueberry anthocyanins purified by LS-305 resin was77.05,which was 12.63 times that of the color value of the crude extract,which met the requirements of industrial production.And this method was easy to operate and scale up,and had the potential for industrial production.In the stability experiment of blueberry anthocyanins,the order of stability of blueberry anthocyanins under different light conditions was dark>indoor natural light>strong sunlight.Temperature has a great influence on the stability of blueberry anthocyanins.The thermal degradation process of blueberry anthocyanins could be well described by the first-order reaction kinetics model.Blueberry anthocyanins were more unstable in higher temperature conditions.When p H≤4.0,blueberry anthocyanins were more stable,and its half-life was about 20 times longer than that under the condition of high p H.The stability of anthocyanins in aqueous solution was better than that in alcohol-aqueous solution under the same conditions.Therefore,it was suggested that the low temperature,avoid light and acidic conditions should be adopted for industrial production and storage of blueberry anthocyanins.