High-intensity Pulsed Electric Field-assisted Extraction, Stability And Antioxidant Activity Of Procyanidins From Vitis Amurensis Seeds

Vitis amurensis in C hina is rich in resources,which is the main raw material of wine industry in Northeast C hina.But the level of wine by-products exploitation and utilization is low.Procyanidins?PC?was reported to be an active ingredient,which exhibited various biological and pharmacological activities.There are abundant PC compounds in Vitis amurensis seeds.Therefore,the study on the extraction of PC from Vitis amurensis seeds can effectively improve the utilization value of Vitis amurensis,bringing important economic and social benefits.An efficient preparation process for the extraction of PC from Vitis amurensis seeds was proposed.The stability and antioxidant activity of PC with different polymerization degrees were investigated.The work provides a new way for the utilization of processing by-products of Vitis amurensis,and provides the theoretical basis and technical reference for the application of PC in health products.The main research performed and the correspondent results obtained are as follows:1.A fast high-intensity pulsed electric field?PEF?technique for the extraction of PC from Vitis amurensis seeds was proposed.The PC yield was selected as the response of the design experiments.O n the basis of the single-factor test,a three-level-four-factor BBD was applied to obtain the highest PC yield.The optimal conditions were as follows: pulse number,10;electric field intens ities,25 k V/cm;ratio of material to liquid,1:21 g/m L;ethanol concentration,63%.Under above optimum conditions,the yield of PC was 8.23%,which was ethanol extraction,ultrasonic-assisted extraction and microwave-assisted extraction over 1.78,1.56 and 1.63 times,respectively.The comparison of different extraction methods showed that the PEF was an effective method for the extraction of PC.Under the optimum conditions of PEF extraction,the yield of PC was increased by 15.43% by adding sodium hexametaphosphate.2.The crude PC extracts from Vitis amurensis seeds was further purified by macroporous resin.According to the captive test,the adsorption and desorption performances of seven kinds of resins adsorbent to PC were studied.The results showed that the effect of HPD750 was the best.The Langmuir and Freundlich equation were used to analysis the adsorption isotherm of PC at different temperature.The results indicated that Freundlich adsorption isotherm equation can better describe the effect of temperature on HPD750 resin adsorption of PC.It suggests the adsorption behavior of a monomolecular layer as well as a multi-molecular layer.The adsorption capacity was the highest at the concentration of PC of 5.0 mg/m L and the adsorption flow rate of 1.0 m L/min.The saturated adsorption was finished when the sample solution reached 11.25 BV.PC was completely desorbed using 4.25 BV eluent?70% ethanol as eluent?with a desorption rate of 0.5 m L/min.The purity of the refined PC was 93.69%.3 Based on differences of solubility and polarity of PC compontents in the extracts solution,the PC extract was classified by ethyl acetate according to the degree of polymerization.The average degree of PC1,PC2 and PC3 was 3.4,2.9 and 5.46,respectively.The test results showed that the ethyl acetate extraction could effectively separate oligomeric PC and polymeric PC.The results of IR spectra show that,the PC from Vitis amurensis seeds was mainly composed of procyanidin.By HPLC-MS qualitative analysis,the PC extract from Vitis amurensis seeds was mainly consists of catechin,epicatechin monomers,B type procyanidolic dimer,B type procyanidolic trimer and a small amount of gallic acid two dimer monoester.4.The stability of PC from Vitis amurensis seeds with different conditions was studied.The PC was found to be very stable under low temperature,light-avoiding and weakly acidic conditions.Three different sterilization methods were found to affect the stability of PC to different extents,which high pressure steam sterilization had the largest effect,boiling sterilization was in the middle and pasteurization had the least effect.PC could be damaged by Fe²⁺?Fe³⁺ and Cu²⁺,and other tested metal ions had little effect.The addition of glucose,sucrose,salt,beta cyclodextrin,citric acid and Vc had a protective effect on the thermal stability of PC.The effect of citric acid is the most obvious.The thermal degradation process of PC from Vitis amurensis seeds was in accord with the first order reaction kinetics model.Polymeric PC in different conditions is more stable,which may be related to its composition unit,molecular weight and steric factors.5.The total antioxidant capacity,reducing power,DPPH radica l scavenging capacity,Fe²⁺ chelating ability and the ability of inhibiting lipid oxidation of the samples were studied.The results showed that the PC from Vitis amurensis seeds exhibited great antioxidant activity in the antioxidant system.There was a dose-effect relation in a certain concentration range,and the activities were becoming stronger with the increase of concentration.In addition to the DPPH radicals scavenging capacity,the antioxidant capacity of the PC purified by HPD750 macroporous resin was significantly improved in the other antioxidant systems.For most antioxidant systems,oligomeric PC has stronger antioxidant capacities.