Study On The Extraction And Stability Of Anthocyanins From Mulberry Pomace

Mulberry is a mature fruit of perennial woody plant Morus alba L.belonging to the genus Moraceae,the family of Morus,which is rich in nutrients and functional ingredients.At present,mulberry is mainly used in the production of mulberry juice,mulberry wine and mulberry vinegar and mulberry pomace is the main by-product during its processing.Many studies have shown that mulberry pomace remain a large number of anthocyanins,which are related to antioxidant,anti-cancer,hypoglycemic,hypoglycemic and protection the cardiovascular system.Therefore,it is of positive significance to make rational use of mulberry pomace and construct comprehensive utilization of waste resources.In this paper,the mulberry pomace provided by enterprises was used as raw material,the extraction,stability,structure identification and degradation mechanism of anthocyanins from mulberry pomace were systematically studied.The main research contents and conclusions are as follows:1.Study on the extraction of anthocyanins from mulberry pomaceThe extract effects of CSE,MASE and DES on mulberry pomace anthocyanins had been researched.Through single factor and orthogonal experiment,the optimum process parameter of CSE were as follows:ethanol volume fraction 60%,p H 3.5,extraction temperature 50?,extraction time 120 min,solid to liquid ratio of 1:70 g/m L,the maximum amount of anthocyanins was 33.18 mg/g;The optimal extraction conditions for MASE by response surface methodology were:ethanol volume fraction 75%,p H 3.5,microwave power 700 W,extraction temperature50?,microwave time 20 s,solid to liquid ratio of 1:50 g/m L,the maximum amount of anthocyanins was 34.63 mg/g;The optimal extraction conditions for DES by response surface methodology were:Choline chloride/1,2-propanediol?molar ratio 1:2,water content 40%?as extraction solvent,microwave power 600 W,extraction temperature 40?,microwave time 40 s,solid to liquid ratio of 1:50 g/m L,the maximum amount of anthocyanins was 36.05 mg/g.After comparison with anthocyanins yields of CSE,MASE and DES,the results showed that MASE and DES were better than CSE,which obviously improved extraction efficiency and extraction yield;Compared with DES,MASE is simple to operate,and the reagent of MASE is easy to recycle,finally,MASE was determined to be the best extraction method for anthocyanins.2.Study on the stability of anthocyanins from mulberry pomaceThe stability of mulberry pomace anthocyanins were studied.The results indicated that p H value had great impact on absorption spectrum,color and stability,as p H value increased,the stability of anthocyanins decreased;When the temperature is no more than 60?,anthocyanins are relatively stable,Wile the temperature is more than 60?,the stability of anthocyanins decreases sharply after the high temperature and long time treatment.At the same time,the retention rate of anthocyanins also showed a downward trend,even at a lower temperature storage,anthocyanins will still degrade with the lengthening of storage time;Under the exposure of outdoor strong natural light,anthocyanins are rapidly degraded;Al³⁺and Fe³⁺have the hyperchromic effect,but Fe³⁺will cause the degradation of anthocyanins,making the maximum absorption wavelength of anthocyanin hypsochromic shifts,Al³⁺inhibited anthocyanins degradation.Na⁺in low concentration inhibited anthocyanins degradation;Cu²⁺will cause anthocyanins Browning and accelerate anthocyanins degradation;Ca²⁺and Mg²⁺have little effect on the stability of anthocyanins;Anthocyanins content decreased in alcohol fermentation and acetic acid fermentation.3.Preliminary study on the structure and degradation mechanism of anthocyanins from mulberry pomace1 The structure of anthocyanins was identified by UHPLC MS/MS and UV-Vis,which identified that there were 6 monomer components,respectively cyanidin-3-sophoroside,cyanidin-3-glucoside,cyanidin-3-rutinoside,pelargonidin-3-glucoside,pelargonidin-3-rutinoside and cyanidin.The contents of 6 components were 0.52%,54.46%,38.88%,5.37%,0.66%,0.11%.2 The purified anthocyanins were heated at 100?by water bath for 0,4,8 h,and their degradation products were detected by UHPLC-MS/MS,and the degradation path was speculated to be that 3-glucosidic bond of cyanidin glycosides was ruptured to cyanidin,hydrone attack the C-ring of cyanidin to produce hydroxyl groups,which is further oxidized to form quercetin.Another degradation path was speculated to be that 3-glucosidic bond of cyanidin glycosides was ruptured to cyanidin,which is cycled into unstable ketones,which eventually form protocatechuic acid and 2,4-dihydroxybenzoic acid.3 The changes of composition and proportion of anthocyanins after illumination were analyzed by UHPLC-MS/MS.Five anthocyanin monomers were detected in the samples after illumination,namely cyanidin-3-sophoroside,cyanidin-3-glucoside,cyanidin-3-rutinoside,pelargonidin-3-glucoside and pelargonidin-3-rutinoside.The relative contents were 2.12%,46.52%,42.95%,6.76%and 1.65%,respectively,the ratio of cyanidin-3-glucoside and cyanidin-3-rutinoside decreased from 1.38 to 1.08,the proportion of cyanindin-3-rutinoside increased,indicating that the stability of cyanindin-3-rutinoside was higher than that of cyanidin-3-glucoside.4 The effects of alcohol fermentation and acetic acid fermentation on anthocyanins composition were analyzed by UHPLC-MS/MS.There are 5 kinds of anthocyanins monomers detected in mulberry juice and mulberries wine,namely cyanidin-3-sophoroside,cyanidin-3-glucoside,cyanidin-3-rutinoside,pelargonidin-3-glucoside and pelargonidin-3-rutino-side,while only 1 kind of anthocyanins monomer was detected in mulberry vinegar samples,indicating that acetic acid fermentation had a greater effect on anthocyanin stability.