Effect Of Steam Explosion Andalkaline Pretreatment Onprocyanidins Of Chardonnaygrape Seeds

Procyanidin(PC)has good pharmacological activities such as anti-oxidation and anti-tumor.One of the sources is grape seeds,but there are more than 50%non-extractable procyanidins(the degree of polymerization is relatively high)in grape seeds.And more than 65%of the extractable procyanidins are polymeric procyanidins(PPC).The alkali method has been proven to successfully depolymerize A-type proanthocyanidins.The steam explosion(SE)method has been proven to successfully increase flavonoid yield,depolymerize lignin and cleavage glycosidic bonds.Therefore,the focus of this research is to study the effect of SE and alkaline pretreatment on releaseing oligomeric procyanidins(OPC)and depolymerizeing polymeric procyanidins.In this study,the microstructures were observed by scanning electron microscopy.The total procyanidins and total phenol content were evaluated by vanillin method and Folin-Ciocalteu method.The polymerization unit and the mean degree of polymerization of PC were evaluated by thiolytic degradation-RP-HPLC.And the composition of the PC fractions were characterized by NP-HPLC and each peak was distinguished in the light of the peak time of the standards.In order to evaluate the depolymerization effect,three in vitro antioxidant activity experiments of DPPH,FRAP and ABTS were used for evaluation.The following are important research contents of steam explosion and alkali method:1.To investigate the effect of SE pretreatment on the extraction and depolymerization of procyanidins.SE destroyed the hard and dense fiber structure of grape seeds and produce more porous holes,but the loose structures and surface area increase did not promote the extraction of procyanidins.Compared with the control group,the mDP of the exploded groups were significantly reduced,the antioxidant activities in vitro were significantly enhanced,and the peak area growth ratio(PAGR)of monomers and epicatechin-3-O-gallate(ECG)were significantly increased.From the above results,we tried to postulate the depolymerization mechanism of procyanidins.2.To investigate the effect of alkaline pretreatment on the extraction and depolymerization of procyanidins.Study different alkali pretreatment temperatures(40,60,80?),time(15,30,60 min),alkali concentration(0,1,2,4,6 mol/L),and determine the effects of mDP,OPC component,OPC content and in vitro antioxidant activity.The results showed that compared with the control group 0 mol/L NaOH,treated at 60? for 15 min,10 mol/L NaOH,60? treatment for 15 min is the best treatment conditions.Finally,the effects of alkali treatment on the release and depolymerization of grape seeds procyanidins were inferred based on the changes of OPC components and OPC content.In summary,this study provides a new way of thinking for the production of OPC.In this study,two solutions of SE and alkali method were proposed for the extraction and depolymerization of procyanidins.The experimental results of two schemes proved that SE method is an efficient and clean depolymerization method,but for the increase of OPC,only the monomers and ECG components increased significantly,and other components showed a downward trend.The alkali method is a method for efficient depolymerization and OPC yield increase,but the salt produced by the neutralization reaction will become the bottleneck of industrial production.Although the ethyl acetate extraction method used in this study is effective,it also causes part of the product loss.In summary,although the SE and alkali method have achieved phased results,more research is needed to achieve industrial production.