Study On The Methods For Comprehensive Utilization Of Anthocyanins And Starch In Purple Sweet Potato

Purple sweet potato anthocyanins?PSPAs?are a natural food additives.PSPAs were usually extracted using citric acid aqueous as solvent in production process,in which some disadvantages including solvent-consuming,high cost and environment pollution were always found and a mass of starch were abandoned.In this work,the new methods for extraction of PSPAs were developed with high etractive efficiency and small quantity of solvent.The main conclusions are as follows.1.A method of microwave-assisted continuous extraction of anthocyaninsA new method of microwave-assisted continuous extraction?MACE?of anthocyanins from purple sweet potato?PSP?using a small quantity of acidic ethanol aqueous as solvent was developed in this work.Firstly,The extraction conditions of PSPAs were optimized by Response Surface Methodology?RSM?and the optimal parameters were as follows:solid-to-liquid ratio of 1:3,ethanol concentration of 30%with a small quantity of critic acid as regulating reagent of pH,microwave irradiation power of 320 w,extraction time of 500 s.Under the conditions,the yield of anthocyanins was 92.16%?RSD=1.45%,n=3?,which was a relative error of-0.64%compared with the predicted value?92.75%?by model of RSM.The pigment was obtained by colunm chromatography of macroporous resin with a yield of 5.0%and a color value of 39.67(E^1%_1cm,530 nm).The anthocyanins constituents extracted by MACE were compared with that of ultrasound-assisted extraction with citric acid aqueousby HPLC-ESI-MS².The analytical results revealed that the main constituents were accordant in both extracts.Compared with other extraction methods,MACE provided a new method according with principle of green chemistry:small quantity of solvent,short time and high efficiency.The character of residues from MACE were similar to fresh PSP which is beneficial to comprehensive utilization.2.Microwave assisted extraction of anthocyanins with phosphoric acid as solventThe method of microwave assisted extraction?MAE?of anthocyanins from PSP with phosphoric acid as solvent was optimized by RSM.The best extraction conditions of anthocyanins were as follows:microwave power of 400 w,phosphoric acid concentration of 1.2%,liquid-solid ratio of 15:1 and microwave irradiation time of 4 min.Under the experimental conditions,the extraction yield of anthocyanins was 93.57%?RSD=0.937%,n=3?,which is a relative error of-3.46%compared with the predicted value?96.92%?by model of RSM.The pigment was obtained by colunm chromatography of macroporous resin with a yield of 0.48%and a color value of 42.84(E^1%_1cm,530 nm).The HPLC analysis indicated that the main constituents of anthocyanins extracted by MAE were similar to that of traditional percolation method.The character of MAE of anthocyanins from PSP with phosphoric acid as solvent is high efficiency and low amount of acid compared with citric acid extraction method.3.Synthesis of alkyl polyglucoside from starch sugarAlkyl polyglucoside was synthesized with the starch of PSP as material in this paper.The yield of alkyl polyglucoside from the starch sugar of MAE or the residue of MACE was 96.4%and 90.6%,respectively.Their emulsification was 5 min and 2min,respectively.Their foaming was 28.57%and 23.81%,respectively.Their stabilization was 32.97%and 27.27%,respectively.The components of samples were analyzed by IR.The result indicated that the structure of the products was similar to that of commercial alkyl polyglucoside?0810?.