The Fermentation And Component Analysis Of Chestnut Jujube Fruit Vinegar

Chinese chestnut,also known as chestnut,is a kind of nut.It has the reputation of“king of dried fruit”.It is rich in starch,protein,vitamins,unsaturated fatty acids and flavonoids.It has the functions of nourishing the stomach and strengthening the spleen and preventing high blood pressure,coronary heart disease and other effects.In the storage process,it is easy to mold,insect,germination and water loss,because fresh chestnut kernel has high water content and high respiratory intensity,which causes a lot of waste of chestnut resources.At present,it is insufficient for further processing of chestnuts,and it also causes a large amount of chestnut to be wasted.The fruit vinegar is a kind of acid seasoning with rich nutrition and good flavor,which is made from fruit raw materials or juice by yeast ethanol fermentation and acetic acid fermentation of acetic acid bacteria.This study was aimed at further processing of Chinese chestnut resources.The separation,screening and identification of saccharomyces cerevisiae,fragrant yeast and acetic acid bacteria.The chestnut was used as main material and red jujube was used as supplementary materials,and the enzymatic hydrolysis process of chestnut jujube was studied,the fermentation process of fruit vinegar was optimized,and the analysis of various nutrients in fruit vinegar provided theoretical basis for the development and industrialization of chestnut jujube fruit vinegar.The main research contents are as follows:1.The isolation and screening of saccharomyces cerevisiae,fragrant yeast and acetic acid bacteria.The saccharomyces cerevisiae was isolated from the fermented grains,the fragrant yeast was isolated from the commercially available Anqi fragrant yeast,and the acetic acid bacteria was isolated from solid fermentative substrate of vinegar.And the identification of the obtained saccharomyces cerevisiae,fragrant yeast and acetic acid bacteria was carried out.2.The enzymatic hydrolysis process of chestnut jujube juice was optimized by single factor experiment.The results showed that the addition of high temperature resistant amylase was 175 mg/kg,and the best treatment was carried out in a constant temperature water bath at 90?for 50 min.The addition of glucoamylase was 15 mg/kg,and the best treatment was carried out in a constant temperature water bath at 55?for 30 min.The addition of pectinase was 150 mg/kg,and it was best to treat it in a constant temperature water bath at 50?for 2 h.3.The optimization of ethanol fermentation and acetic acid fermentation conditions.The results showed that fermentation time,fermentation temperature,inoculation volume and inoculation proportion were optimized by orthogonal test.The optimal conditions for ethanol fermentation were temperature 30?,time 5 d,the volume fraction of inoculum was 10%,the sucrose amount was 10%,and the inoculation ratio of Saccharomyces cerevisiae,fragrant yeast and lactic acid bacteria was7:3:10.The process conditions of acetic acid fermentation were optimized by single factor test.The results showed that the optimum conditions for acetic acid fermentation were temperature 28?,time 5 d,the inoculation amount was 10%,and the initial ethanol was 8%.The results were optimized by the response surface test method.The highest acidity of vinegar was 5.6 g/100mL.The results were consistent with the best conditions obtained by single factor test.The chestnut jujube fruit vinegar obtained by the above optimized method is clear,has the unique color of chestnut,has the unique flavor of chestnut and vinegar,the total acidity of the vinegar(calculated as acetic acid)is 5.3±0.3 g/mL,and the total number of bacteria?10000/mL;E.coli?3/100mL,no pathogenic bacteria(intestinal pathogens)were detected,in line with national food vinegar hygiene standards GB 2719-2003.4.The main nutritional components of fruit vinegar and its antioxidant activity were analyzed.The results showed that the contents of polyphenols,flavonoids,peptides and V_c in chestnut jujube fruit vinegar were 0.145 g/L,0.494 g/L,1.431 g/L and 0.0358 g/L.The contents of tartaric acid,malic acid,lactic acid,acetic acid,citric acid and succinic acid were determined by High Performance Liquid Chromatography to be 0.28 g/L,0.437 g/L,0.902 g/L,24.428 g/L,0.232 g/L and 1.535 g/L.The analysis of volatile substances in vinegar by Headspace-Solid Phase Microextraction-Gas Chromatography-Mass Spectrometry showed that there were 30 kinds of volatile flavor substances in vinegar,and the contents of esters,acids and alcohols were 2.692%,55.939%and 22.509%.According to the analysis and identification of amino acid automatic analyzer,the fruit vinegar contains 33 kinds of free amino acids,and the total content is 64.446 mg/L.Under the same conditions,the DPPH free radical scavenging rate of chestnut jujube fruit vinegar reached at 97.05%,which showed stronger DPPH free radical scavenging ability.