Lactic Acid Bacteria Enhance The Antioxidant Activity Of Jujube Polyphenols

Phenolic acid is potential highly efficient natural antioxidants because they can scavenge free radicals,inhibit lipid peroxidation,slow down or prevent the progression of auto-oxidation chain reactions,therefore received widespread attention.Jujube is rich in phenolic acids,mainly in the bound state,but its bioavailability is very low,which greatly reduces its biological effects.According to studies,lactic acid bacteria can convert bound phenolic acids to free phenolic acids and increase their antioxidant.Therefore,different lactic acid bacteria was used to ferment jujube pulp,then the content,composition and antioxidant activity were determined to select the optimal strains and the optimal fermentation time,and a method for simultaneous determination of six phenols acid by GC-MS was established.Changes of phenolic acid in jujube pulp during simulated gastrointestinal digestion was studied.It provides production process parameters for jujube pulp products containing high bioavailability polyphenols,and provides a new development path for jujube deep processed products,which will have important practical significance for the development of jujube processing industry.This paper mainly includes three parts and the results as follows:1.Simultaneous determination of six phenolic acids in jujube by GC-MSGC-MS was used to simultaneously determine six phenolic acids in jujube including salicylic acid(SA),4-hydroxybenzoic acid(4-HBA),vanillic acid(VA),2,5-dihydroxybenzoic acid(DHB),protocatechuic acid(PA)and p-coumaric acid(p-CA).Meanwhile,the column,temperature programmed and derivatization condition was selected.Finally,the Rtx-5 capillary column(0.25 mm x 30 m,0.25?m)was confirmed to use;The samples were derivatized by BSTFA(containing 1%TMCS)at 35? for 30min.Under these conditions,the six phenolic acids were detected in the jujube,and the linear relationship was good(R2?0.994).The detection limit,recovery rate and relative standard deviation can meet the detection requirements.The method can apply to the qualitative and quantitative analysis of the six phenolic acids in three different varieties of jujube,which provides a new method for the study of phenolic acids in later date2.Effects of lactic acid bacteria fermentation on free phenolic acid and antioxidant ability of jujube pulbJujube pulb was fermented by five lactic acid bacteria including La,St,Lc,Ld and Lp,then the content,composition and antioxidant activity of free phenolic acid were determined.The results showed that five lactic acid bacteria can increase the total free phenol content,DPPH radical scavenging ability and FRAP antioxidant capacity,and Lp had more advantages than the other lactic acid bacteria in the ability of improving the content of free phenolic acid and antioxidant ability.After 24 h,the total free phenol content,DPPH radical scavenging ability and FRAP antioxidant capacity were increased by 41.7%?139.3%?53.8%;SA,4-HBA,VA,PA,and p-CA levels increased by 22.8%to 121.1%.Therefore,jujube pulb fermented 24h by Lp have high antioxidant,it might be used and developed as functional food.3.Effects of fermentation on release and absorption of free phenolic acid from jujube pulp in simulated digestion in vitroJujube pulp fermented by Lp was simulated in vitro and digested.Results indicated that,during gastric digestion stage,the release of free phenol content,DPPH radical scavenging ability and FRAP antioxidant capacity of jujube after fermented were increased by 19.9%?71.6%,SA and PA were increased by 18.3%and 129%,but But p-CA decreased 10.3%-33.3%.During intestinal digestion process,the release of free phenol content,DPPH radical scavenging ability and FRAP antioxidant capacity of jujube after fermented were increased by 25.5%?46.0%,and SA,PA and p-CA increased by 26.1%-99.9%.In addition,the bioavailability of jujube pulp after fermented increased significantly increased by 62.7%?68.6%.