| At present,the mulberry fruit in the mulberry planting base of Guizhou enterprises is mainly used for the production of mulberry fruit juice and fruit wine.Some studies have shown that mulberry pomace and frost mulberry leaves are rich in polyphenols and flavonoids,therefore,it is of important practical significance for its comprehensive utilization.This article mainly uses mulberry pomace and frost mulberry leaves as raw materials to brew fruit vinegar.The fermentation process conditions,physical and chemical indicators of different fermentation methods,volatile components and organic acids,antioxidant,hypoglycemic and bacteriostatic effects were studied.The result is as follows:1.Optimization of solid fermentation process of mulberry pomace vinegar: the effects of fermentation time,temperature,yeast inoculation quality and sucrose addition quality on alcohol content and anthocyanin were investigated in alcohol fermentation stage of mulberry pomace vinegar.The results have shown that the best conditions of the alcohol fermentation: fermentation time 5d,yeast inoculation quality 0.04% ～ 0.05%,fermentation temperature 26 ℃ ～ 28 ℃ and sucrose addition quality was 12～16%.Single factor and optimization experiments were carried out in the acetic acid fermentation stage of mulberry pomace vinegar.The best conditions for solid fermentation of mulberry pomace vinegar: vinegar moisture content of 79.5%,initial alcohol content of 7.7% vol,fermentation temperature of 32.1 ℃,inoculation quality of acetic acid bacteria of 12.0%.As a result,the production of acid was 5.02g/100 g,the acidity of the vinegar acid was not far from the theoretical value by the verification experiment.2.Preparation of mulberry fruit vinegar by different fermentation methods: The changes of anthocyanin,acidity,polyphenols and flavonoids in the process of alcohol fermentation and acetic acid fermentation of fruit vinegar with different fermentation methods were studied.In the alcohol fermentation stage,the samples of different fermentation methods showed little difference in alcohol content and reducing sugar content.On the whole,the anthocyanin showed a downward trend,and the total acid and polyphenol content showed a trend of first increasing and then decreasing.Solid one(add frost mulberry leaves in the acetic fermentation stage),three(add bran in the acetic fermentation stage),semi-solid mash and liquid fruit wine showed an increasing trend of flavonoid content relative to the initial value,while solid two(add frost mulberry leaves in the alcohol fermentation stage)showed a downward trend.In the acetic acid fermentation stage,the total acid and non-volatile acid of fruit vinegar with different fermentation methods showed a trend of rising first and then falling,the amino nitrogen showed a rising trend,and the contents of polyphenols,flavonoids,and anthocyanins all showed a downward trend.After centrifugal sterilization,the total acid content of solid one,two,three,semi-solid and liquid fruit vinegar were4.98 g / 100 m L,4.62 g / 100 m L,5.43 g / 100 m L,3.42 g / 100 m L,6.32 g / 100 m L,respectively.The solid-fermented fruit vinegar had the highest polyphenol and flavonoid content,and was 0.292 g /100 m L and 0.224 g / 100 m L,respectively.According to the sensory analysis,the solid-mulberry fruit residue vinegar had a higher sensory score,and had the inherent color of mulberry and frost mulberry leaves.The fruit flavor and frost mulberry leaves were more intense,the acidity was softer,and the taste was slightly sweet.3.Study on volatile components and organic acids in different fermentation stages ofmulberry fruit vinegar: GC-MS was used to analyze the volatile substances in the samples,and high performance liquid chromatography was used to analyze the organic acid content of the samples.The changes of volatile substances and organic acids of solid mulberry fruit residue vinegar and liquid mulberry fruit juice vinegar in the stages of raw mash,fruit wine and fruit vinegar were mainly analyzed.A total of 386 volatile components were detected in 6 kinds of fermentation samples.The raw materials of mulberry fermentation mainly included ethyl acetate,isoamyl acetate and isobutanol and other volatile components with fruit aroma;after alcohol fermentation,alcohols and esters Substantial increased in substances,the main volatile components such as ethanol,phenethyl alcohol,ethyl caprate,ethyl caprylate and other volatile components gave fruit wine and wine mash rich fruity and mellow aroma;After acetic acid fermentation,the alcohols and aldehydes were partially oxidized,the esters were reduced,and the acids were significantly increased.The flavor substance imparted floral and vinegar flavors to fruit vinegar.The solid fermented pomace vinegar sample(164 volatile components in total)was more abundant than the liquid fermented fruit vinegar sample(133 volatile components in total).6 kinds of fermentation samples were analyzed for organic acid content,and a total of 10 different organic acids were detected.Among the detected organic acids,tartaric acid,lactic acid,and acetic acid were the main organic acids in liquid mulberry juice and solid raw mash;The content of oxalic acid,malic acid,tartaric acid and acetic acid in fruit wine decreased slightly,the content of succinic acid in fruit vinegar increased slightly,and the content of acetic acid increased significantly.The content of acetic acid in liquid fruit vinegar and solid pomace vinegar were56.24 g/L and 45.83g/L.4.Functional study of mulberry pomace vinegar: The differences in antioxidant,hypo glycemic and antibacterial functions between solid-state fermented mulberry pomace vinegar and liquid-fermented mulberry fruit vinegar,commercially available grape vinegar,apple v inegar,balsamic vinegar,and white vinegar were investigated.Regarding the antioxidant ca pacity of different fruit vinegars,solid mulberry pomace vinegar,liquid mulberry fruit juic e vinegar and grape vinegar had better free radical scavenging ability,and their DPPH fre e radical scavenging rates were 92.62%,90.62% and 87.15%,respectively.The hydroxyl radical scavenging rates were 77.03%,69.18%,and 65.88%;the superoxide anion radical s cavenging rates were 90.45%,93.36%,and 92.58%;the iron reducing power absorption va lues were 1.803,1.594,and 1.612;The basic clearance rates were 93.57%,91.86%,and 91.71%,followed by balsamic vinegar,apple vinegar,and white vinegar.The concent of po lyphenols and flavonoids in solid mulberry pomace vinegar are higher,so the antioxidant capacity was stronger.The order of different vinegar hypoglycemic capacity was as follow s: solid mulberry pomace vinegar> apple vinegar> liquid mulberry juice vinegar> grape vi negar> balsamic vinegar> white vinegar solid,solid mulberry pomace vinegar and apple vi negar had better hypoglycemic ability.The α-glucosidase inhibition rates of solid mulberry pomace vinegar and apple cider vinegar were 79.14% and 76.66%,and the α-amylase in hibition rates were 75.98% and 72.97%,respectively.Solid mulberry pomace vinegar and liquid mulberry fruit juice vinegar had good antibacterial effect on Escherichia coli and S taphylococcus aureus,and the six kinds of vinegar had no obvious antibacterial effect on Candida albicans. |
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