Extraction And Determination Of Polyphenols From Persimmon Fruits And Effects Of Mixed Fermentation On Persimmon Wine

Shaanxi province is rich in persimmon resources.The polyphenols and condensed tannins of six different varieties of persimmon fruits were extracted and determined in this study.The changing rules in the process of persimmon growth were obtained.The mature persimmon fruits were used as raw material to ferment the persimmon wine by the mixed fermentation method.The effects of mixed bacteria fermentation on the basic physicochemical indexes,phenolic substances,organic acids and aroma substances of persimmon wine were explored.(1)Ultrasonic-assisted extraction was used to extract polyphenols and tannins from persimmon fruits.The contents of total phenols and condensed tannins of the six varieties of persimmon in early June were highest,after which the contents gradually decreased.The contents of total phenols and condensed tannins of the pollination content astringent persimmon showed a slight increase at the beginning of September,and then decreased until reaching the lowest point at maturity.In each growth stage,the order of the content of polyphenols and condensed tannins in different varieties of persimmon fruits was: pollination content astringent>pollination variant astringent>pollination variant nonastringent>pollination content nonastringent.Therefore,the astringent persimmon fruits in early June can be selected as a raw material for extracting polyphenols and condensed tannins.(2)The content of total phenols and condensed tannins in alcohol-fermented persimmon wines(CK group)was higher than that of malolactic-fermented persimmon wines(SIM,S-24 and SEQ groups).The total phenolic content of persimmon wine in CK group was significantly higher than that in the other three groups.There was no significant difference in total phenolic content between SIM group,S-24 group and SEQ group.There was no significant difference in the condensed tannin content between the four groups.Therefore,inoculation of lactic acid bacteria in persimmon wine for malolactic fermentation reduces the content of total phenols and condensed tannins in persimmon wine,and the inoculation timeof lactic acid bacteria will not have a significant effect on it.Alcohol-fermented persimmon wine(CK group)had higher antioxidant capacity than persimmon wine fermented with malolactic acid(SIM,S-24 and SEQ groups).(3)A total of 13 monophenols were detected in persimmon wines,of which gallic acid,catechin,and phthalic acid were the main monomelic phenols.Persimmon wine inoculated with lactic acid bacteria for malolactic fermentation will reduce the content of phenolic substances such as gallic acid,protocatechuic acid,catechin,and phthalic acid in persimmon wine;and chlorogenic acid,vanillic acid,and caffeic acid phenolic compounds such as ferulic acid slightly increased compared with the CK group.The content of phenols in the SIM,S-24 and persimmon wines after malolactic fermentation was lower than that in the CK group.(4)After the fermentation,the content of tartaric acid,malic acid,citric acid and succinic acid in the persimmon wine decreased,and the lactic acid content increased.The oxalic acid content was not significantly different from that before fermentation.In malolactic fermentation,the inoculation time of lactic acid bacteria had no significant effect on the organic acid content in persimmon wine.(5)A total of 58 aroma substances were detected in persimmon wines,including 29 esters,7 alcohols,7 aldehydes and ketones,3 acids,8 alkane,and 4 other substances.There are 32 kinds of aroma substances common to wine.Among them,there are many types of esters and their contents are high.The main ester compounds detected in persimmon wine include ethyl phthalate,ethyl caproate,isoamyl acetate,ethyl octanoate;the main alcohol compounds include(±)-2-methyl-1-butanol,D-(-)-2,3-butanediol,1-octanol,phenethyl alcohol;The main acid compounds are acetic acid,caprylic acid and caproic acid.In the persimmon wine fermented with malolactic acid,the different inoculation time of lactic acid bacteria had a certain influence on the composition and content of aroma substances in the wine.