Study On Polysaccharides And Nitrogenous Substances During Fermentation Process Of Kiwifruit Wine

Kiwi wine refers to the fruit wine which is fermented with yeast from fresh kiwifruit.Kiwi wine is rich in a variety of nutrients,such as ascorbic acid,polyphenols,polysaccharides and amino acids.These ingredients not only affect the nutritional composition of kiwifruit wine,but also are closely related to the sensory quality and stability.With Hayward,Qinmei and Hongyang as raw material,six kinds of kiwi wines were fermented from whole fruit and juices respectively.The changes of a variety of nutrients during the fermentation were investigated.And the effects of fermentation with pomace on the quality of kiwi wines were analyzed.The main findings are as follows:(1)The changes of total polyphenols,VC and tannin contents in wines varied with the kiwifruit varieties and fermentation methods.Compared with wines fermented with juice,the contents of polyphenols,tannin and the reducing power of the wines could be improved by fermentation with pomace,but the results of VC showed a decrease oppositely.However,there was no obvious pattern on the free radical scavenging rates of DPPH and ABTS~+·.(2)Determine of kiwi wine total polysaccharides during fermentation by phenol-sulfuric acid method.The monosaccharides composition,basic properties and antioxidant activities of crude polysaccharides were determined.The results showed that the changes of total polysaccharides contents during six kinds of kiwi wines fermentation were similar.The contents of total polysaccharides increased first and then decreased,finally remained steadily.Six kinds of kiwi wines crude polysaccharides contained six kinds of monosaccharides:rhamnose,arabinose,xylose,mannose,glucose and galactose.And the Fourier transform infrared spectroscopy of crude polysaccharides were similar.Fermentation with pomace was beneficial to the impregnation of arabinose,arabinan and arabinogalactan and could also change the content of neutral side chains carried by the main chain of rhamnogalacturonan in wines.And fermentation with pomace could significantly improve the uronic acid contents,reduce protein contents of kiwi wines crude polysaccharides.And the antioxidant activities of crude polysaccharides increased following with polysaccharides concentration increase.(3)The changes of the protein content of the six wines were small.The contents of total free amino acids of six kinds of kiwi wines experienced a general rule of rapid decrease and final increase.Sixteen kinds of amino acids were detected by High performance liquid chromatography.There were different in the contents changes of 16 kinds of free amino acids.There was no significant rule in the six amino acids of glutamic acid,glycine,arginine,threonine,tyrosine and lysine.The changes of methionine,valine,isoleucine and leucine were similar:continuously increases,then decreases rapidly and finally increases gradually.The other 4 amino acids(aspartic acid,serine,histidine,phenylalanine)and 2 amides(glutamine,asparagine)showed different trends according to kiwifruit varieties and fermentation methods.In addition,the kiwifruit varieties and the dipped liquor had certain influence on the amino acid contents.(4)A total of 56 kinds of free aroma components were detected in the six kinds of kiwifruit wines,alcohols and esters were the main aroma substances.Fermentation with pomace had a great influence on the aroma components of Hongyang wines,but had little effect on the aroma components of Hayward and Qinmei.