Fermentation Technology Of Passion Fruit Vinegar And Characteristic Chemical Components During The Fermentation Process

With passion fruit juice as raw material,two-stage fermentation and one-stage fermentation were applied to prepare passion fruit vinegar.The chemical components,volatile components and antioxidant properties of fruit vinegar prepared by different processes were measured and evaluated in order to explore the feasibility of one-stage fermentation technology.The main contents include: isolation and screening of excellent acetic acid bacteria suitable for passion fruit vinegar fermentation and its fermentation performance;effect of alcohol fermentation process of passion fruit vinegar on aroma components of alcohol fermentation;comparison of characteristic compounds and antioxidant activity of passion fruit vinegar prepared by two-stage fermentation and one-stage fermentation.The main results are as follows:(1)A strain of acetic acid bacteria with strong capacity of acid production,temperature tolerance,ethanol tolerance and acetic acid tolerance was screened out from vinegar fermented grains in Guangxi folk vinegar mill,which has potential utilization value.The strain was identified as Acetobacter by 16 S r DNA and named as Acetobacter KDA-2.(2)The immobilized yeast and free yeast were used to carry out ethanol fermentation of passion fruit juice,respectively.It was found that the rate of immobilized yeast fermentation of passion fruit juice was low at first and then high,but the final sugar consumption and ethanol production were higher than that of free fermentation,and the ethanol production could be increased by 7.6% by immobilized yeast fermentation.The aroma components of passion fruit juice fermented by immobilized yeast and free yeast were determined by GC-MS.It was found that the volatile components produced by the two fermentation methods were significantly different.The content of ester substances obtained by free yeast fermentation was higher,while the alcohol substances obtained by immobilized yeast were more abundant.(3)By using high performance liquid chromatography and headspace solid phase microextraction GC-MS to analyze and determine the content of organic acids and volatile flavor substances in the four kind of fruit vinegar obtained from two fermentation processes,it was found that most of the volatile compounds and organic acids were reduced in the alcohol and acetic acid fermentation process.However,the degree of reduction of flavor substances in fruit vinegar prepared by one-stage fermentation process is relatively low.Finally,the organic acid characteristics of passion fruit vinegar were determined through principal component analysis.The three kinds of vinegars produced by one-stage fermentation of PFVR,PFVG,and PFVE are acetic acid,oxalic acid,citric acid and malic acid.The two-stage fermentation of vinegar PFV the characteristic organic acids are tartaric acid and succinic acid.It can be concluded that,compared with the two-stage fermentation,the one-stage fermentation of fruit vinegar has more organic acids.(4)By comparing the main bioactive substances and antioxidant capacity of four kinds of passion fruit vinegar prepared by one-stage fermentation and two-stage fermentation,it was found that the contents of vitamin C,total phenols,total flavonoids and total anthocyanins were significantly decreased in the two-stage fermentation process of passion fruit vinegar.The contents of vitamin C,total phenols,total flavonoids and total anthocyanins in passion fruit vinegar could be retained by onestage fermentation.The three kinds of fruit vinegar prepared by one-stage fermentation had better antioxidant capacity.According to the principal component analysis of polyphenols,the three kinds of passion fruit vinegar fermented in one stage are more similar to the composition of passion fruit juice,which can reduce the loss of polyphenols during the fermentation of fruit vinegar.In summary,the use of one-stage fermentation process to prepare passion fruit vinegar has advantages over two-stage fermentation in terms of the retention of organic acids,volatile components and biologically active substances and antioxidant activity.It can be used as an alternative fermentation process for passion fruit during the production of fruit vinegar.