| This topic took green jujube in white ripening stage as the main raw material,optimized the fermentation process of jujube vinegar and analyzed the functional quality of the optimized jujube vinegar.Through the analysis of the changes of organic acids and volatile aroma substances in the fermentation process of green jujube vinegar,as well as the in vitro simulation study on the antioxidant and hypolipidemic function of green jujube vinegar,provide the theoretical basis for the development of jujube vinegar.The main contents are as follows:1.The single factor-response surface was used to optimize the fermentation process of green jujube vinegar with the total acid content as the response value,as follows:Y=5.25-0.057A-0.053B-0.022C-0.15D-0.13AB+0.012AC+0.055AD+0.070BC+2.500E-003BD+0.11CD-0.31A~2-0.31B~2-0.28C~2-0.28D~2,the optimal condition was:initial alcohol content 6%,acetic acid bacteria inoculation amount 8%,fermentation temperature 32?,fermentation time 7 d,the predicted total acid content was 5.27 g/100m L,and the measured value was 5.23 g/100m L,which was in good agreement with the predicted value.2.The organic acids in the fermentation process of green jujube vinegar were analyzed by HPLC.Compared with green jujube juice,the total contents of lactic acid,acetic acid,citric acid and succinic acid in green jujube vinegar increased after fermentation and aging,among which lactic acid and acetic acid changed the most,and reached the highest level at one month of aging.(1.267and 1.131 g/100m L,respectively).Succinic acid content increased during the whole fermentation process,and final level was 0.478g/100m L.The contents of oxalic acid,tartaric acid,citric acid and malic acid decreased from jujube juice to the end of aging,while the contents of tartaric acid and malic acid increased slightly after aging for one month.3.HS-SPME-GC-MS was used to analyze the volatile aroma compounds in the fermentation process of green jujube vinegar.A total of 64 volatile aromatic substances were identified,including 7 alcohols,6 acids,9 aldehydes,28 esters,3 ketones,8 hydrocarbons and their derivatives,and 4 others.Among them,the higher content was ethanol,acetic acid,iso-amyl phenylacetate and iso-amyl aldehyde.The relative contents of alcohol,ester and acid compounds increased gradually,while the contents of aldehyde and ketone compounds decreased gradually with the fermentation.These substances together give jujube vinegar its unique flavor and taste.4.The influence of in vitro simulated digestion on functional properties of green jujube vinegar was evaluated.The contents of total phenols,flavonoids and vitamin C in green jujube vinegar decreased significantly during the simulated gastrointestinal digestion.The content of total acid decreased obviously after simulated gastric digestion,but there was no significant difference in intestinal digestion(P>0.05).Volatile acid content in simulated gastrointestinal digestion declined first and then risen,and the overall content down.After gastrointestinal digestion,jujube vinegar still showed higher DPPH free radical scavenging rate,while ABTS free radical scavenging rate and reducing power decreased significantly.The amount of cholesterol adsorption decreased after gastrointestinal digestion,then there was a slight increase,which was much higher than that of the control check group.Antioxidant activity was significantly positively correlated with the content of total acids,total phenols,volatile acids and flavonoids(P<0.01).With regard to the hypolipidemic activity,the amount of cholesterol adsorption was related to total phenols,flavonoids and acids,while vitamin C has a great contribution to the adsorption of sodium cholate.Therefore,green jujube vinegar still showed effective antioxidant activity and hypolipidemic activity after gastrointestinal digestion. |
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