Process Optimization And Antioxidant Activity Evaluation Of Hovenia Dulcis Fruit Juice Fermented By Lactobacillus

Hovenia dulcis is abundant in sugar,organic acids,vitamins,minerals and other nutrients.Polysaccharides,polyphenolsandflavonoids,representedby dihydromyricetin,have antioxidant,antialcoholic and liver-protecting functions,which are of great value for development and utilization.In this study,the technology of juice making and lactic acid bacteria fermentation were optimized,and the antioxidant activity in vitro and in vivo,storage quality and aroma components of bactericidal and non-bactericidal fermented hovenia dulcis juice were analyzed and evaluated.The results show conclusions as fallows.?1?The optimum conditions for juice preparation were as follows:the addition of pectinase was 0.11%,the hydrolysis time was 2 h,and the hydrolysis temperature was45?.Under these conditions,the extraction rate of kidney jujube was 63.32%,which was significantly higher than that of the group without enzyme?35.12%??p<0.01?.The proportions of mixed strains were as follows:Lactobacillus casei:Lactobacillus brevis:Leuconostoc mesenterica:Saccharomyces cerevisiae 1383=2:2:2:1;and the initial solid content was 25%.Through response surface design,the regression model of fermentationconditionswasobtainedasfollows:Y=0.91+0.013A+0.044B-2.436e-004C-6.221e-003AB-1.131e-004AC-9.844e-004BC+2.872e-003A²-0.028B²-7.245e-003C².The fermentation parameters were as follows:inoculation amount 10%,fermentation time 41 h and fermentation temperature 35?.Under these conditions,the total flavone content was 85.13 mg/100 mL,which was significantly higher than that of raw juice?p<0.05?,while the polysaccharide content and total phenol content were significantly lower?p<0.05?.The sensory score was 85,and the fuzzy comprehensive evaluation value was 0.934.The comprehensive quality is good.?2?After gradient dilution,the antioxidant capacity of non-bactericidal and bactericidal and raw juice in vitro was evaluated.Compared with the raw juice,the total antioxidant capacity of bactericidal and non-bactericidal juice decreased?p<0.05?.The scavenging capacity of DPPH·and ABTS⁺·,and the reduction ability of Fe³⁺decreased not significantly?p>0.05?,while the scavenging capacity of O₂^-·decreased significantly?p<0.05?.Compared with the positive control,the total antioxidant capacity of viable and sterile type was significantly stronger than that of Vc and BHT?p<0.05?.The scavenging capacity of DPPH·and ABTS⁺·,and the reduction ability of Fe³⁺were significantly stronger than those of the positive control?p<0.05?,while the scavenging capacity of·OH and O₂^-·was weaker than that of Vc?p<0.05?.The correlation analysis showed that the total antioxidant capacity of hovenia dulcis fruit fermentation juice was mainly supplied by total phenols,and the correlation coefficient was 0.931.?3?In vivo antioxidant activity of hovenia dulcis fruit fermentation juice was evaluated by Drosophila survival test and biochemical index test.The results showed that,when compared with the control group,the non-bactericidal and bactericidal of different dosage groups?5,10,15 mg/mL?could significantly prolong the average life span of Drosophila?p<0.05?,and improve the T-SOD and T-AOC activities of Drosophila?p<0.05?,and reduced the content of MDA?p<0.05?,and showed a dose-effect relationship.When the dosage was 15 mg/mL,the average life span of male and female Drosophila melanogaster which is feed by non-bactericidal could be prolonged by 66.49%and 61.16%respectively,and that is feed by bactericidal could be prolonged by 48.87%and 47.69%respectively.?4?The hovenia dulcis fruit fermentation juice was filled in heat-resistant PET bottle and stored at 4?.The optimum storage period for non-bactericidal was 20 days,and the number of lactic acid bacteria was 1.04×10⁹ cfu/mL.The optimum storage period for bactericidal was 6 months,and the total number of colonies was 70 cfu/mL.Compared with the pre-storage period,the nutritional and functional components of both non-bactericidal and bactericidal were lost and the sensory quality was decreased in the post-storage period.Among them,the contents of total phenols and flavonoids decreased significantly?p<0.05?,the color difference value?E increased significantly?p<0.05?,the sensory score of non-bactericidal decreased from 89.50 to 81.13,and that of bactericidal decreased from 92.60 to 86.00.?5?By GC-MS analysis,130 volatile components were identified from non-bactericidal,bactericidal and raw juice,and 30 main volatile components were identified.Among them,77 kinds of volatile components were identified in non-bactericidal,with relative content of 94.66%;91 kinds of volatile components were identified in bactericidal,with relative content of 94.22%,ester was the highest;62 kinds of volatile components were identified in raw juice,with relative content of91.46%,acid was the highest.Compared with the raw juice,the total volatile components of fermented juice was increased,and a large number of esters and alcohols were produced,while acids and aldehydes were reduced.By GC-O analysis,totally 41 kinds of aromatic substances were identified,which 30 kinds of aroma components were identified in non-bactericidal,with relative content of 53.51%;26kinds of aroma components were identified in bactericidal,with relative content of48.26%;20 kinds of aroma components were identified in raw juice,with relative content of 28.94%.Vinyl carbonate,ethyl octanoate,ethyl sunate,n-pentanol,phenylethanol and p-vinyl guaiacol are the main aroma-producing substances of hovenia dulcis fruit fermentation juice.They mainly present sweet and sour aroma,baking aroma,fermentation aroma,wine aroma,fruit aroma and rose aroma.Compared with the raw juice,the fermented juice contains more esters and alcohols aromatic substances,so the baking,fermentation and wine aroma are stronger,while the bitterness and sapphire aroma in the raw juice are reduced,and the aroma quality is better than that of the original juice raw juice.