| With the increased health concern,consumers' dietary concepts have changed.They are pursuing natural,green and nutritious food.Fruit and vegetable juice as a natural and healthy drink becomes more and more favorite by consumers due to its rich nutritional value.As main active ingredient in fruit and vegetable juices,phenolic compounds have the effects of radical scavenging and inhibiting the proliferation of cancer cells in the body.However,phenolic compounds in fruit and vegetable juices are mainly composed of bound phenols,which are not easily metabolized and absorbed,affecting their bioavailability in the human body.Therefore,how to change the form of phenolic compounds in fruit and vegetable juices is a problem worth studying.In this paper,the effects of Lactobacillus plantarum fermentation on the composition and antioxidant activity of phenolic in apple juice were studied.The main results for this study are as follows:1.Firstly,the effects of three Lactobacillus plantarum ATCC14917,SHOU.1.12058 and SHOU.1.12061 fermentation on DPPH radical scavenging were studied in crude apple phenolic fermentation system.The results showed that ATCC14917 fermentation significantly increased DPPH free radical scavenging of crude apple phenolic(P<0.05),while SHOU.1.12058 and SHOU.1.12061 had no effect on DPPH free radical scavenging rate(P>0.05).Next,we studied the colony growth curve and pH of the crude apple phenolic during ATCC14917 fermented crude apple phenolic for 24 h,48h and 72 h.The results showed that a rapid growth of L.plantarum was observed during the first 24 h of fermentation.L.plantarum reached a maximum viable cell number of 8.54 log ± 0.05 log CFU/mL at 24 h of fermentation.A drop in the total microbial population was observed after 24 h of fermentation.The pH of apple crude phenolic extracts dropped from 6.11 to 3.68 after 72 h fermentation.Therefore,ATCC14917 can be used for the subsequent experiments.2.Secondly,in the crude apple phenolic fermentation system,we studied the effects of ATCC14917 fermentation on DPPH radical scavenging,total phenolic and total flavonoid content,polyphenol composition and intracellular antioxidant activity during(24h,48 h,72h)fermentation.The results showed that the DPPH radicalscavenging increased 20%,the cell antioxidant activity increased 35% in the fermentation of crude apple phenolic,but total phenolic content and total flavonoid content decreased 17% and 59%,respectively.the total phenolic and total flavonoids decreased by 17%.Further HPLC-MS/MS analysis showed that during fermentation phloridzin and epicatechin gallate in crude apple phenolic were metabolized as phloretin and epicatechin,which had high antioxidant activity increased antioxidant activity of fermented crude apple phenolic.3.Finally,we investigated the effects of Lactobacillus plantarum ATCC14917fermentation(24h,48 h,72h)on the antioxidant activity of apple juice fermentation system.The results showed that DPPH and ABTS radical scavenging in the fermented apple juice increased by 23% and 28%,respectively.The Raw264.7 cell model evaluated the antioxidant activity of fermented apple juice and found that the cell antioxidant activity of fermented apple juice was doubled after fermentation.However,the total phenolic and total flavonoid content was reduced 22.8% and 34.8%,respectively.Further HPLC-MS/MS analysis showed that quinic acid,quercetin-3-O-galactoside,quercetin-3-O-glucoside and phloridin were metabolized into 5-CQA,quercetin and phloretin,which has strong antioxidant activity enhanced the antioxidant activity of fermented apple juice.In summary,In summary,L.plantarum ATCC14917 fermentation modified the phenolic composition of apple juice and enhanced its overall antioxidant capacity.Lactic acid bacteria fermentation may be employed as a simple and valuable biotechnology to enhance the bioavailability of polyphenols of apples.The fermented apple juice could be consumed as a kind of functional food to relieve free radical species-induced disease. |
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