Study On The Physical And Chemical Properties Of Different Polyphenols And Their Effects On Wine Color And Astringency

Plant polyphenols are important secondary metabolites in plants,with complex structures,various types and multiple functions,and they are widely used.Wine polyphenols are composed of natural polyphenols from grape skins,seeds,oak barrels,tannins added by winemakers,and new phenolic compounds produced by the interaction of phenols in wine.These polyphenol compounds are the most important substances in wine,and determine the color and taste of wine.In winemaking,commercial tannins are usually added to change the composition and content of phenolic substances in the wine,thereby adjusting the color and astringency of the wine.Currently,there are few types of commercial wine-making tannins on the market,limited to sources such as grape seed,oak,green tea,and chestnut shells.The research purpose of this subject is to develop new commercial wine-making tannins,and to study their physical and chemical properties and their effects on wine quality,while promoting the full utilization of plant resources.In this experiment,44 different plant materials were selected,and 16 kinds of polyphenol extracts were obtained after extraction,screening and purification.In addition,the 16 plant polyphenols and 6 commercial tannins were selected as the research objects.The total phenol content,total flavanol content,ellagitannin content,protein binding capacity,protein precipitation capacity and astringency were analyzed.In addition,they were added to Chardonnay white wine and Pinot Noir red wine to observe the effects of different sources of plant polyphenols on the color of white wine and the astringency of red wine,in order to find better commercial tannins.The research content and results are as follows:（1）Through the cluster analysis of 44 types of extracted plant polyphenols:total phenols,total flavanol content,bitterness,and astringency,it was found that pomegranate shells,black tea,green tea,chai Puerariae root,grape skin,mint leaves,sorghum shells,oak chips,chestnut shells,raspberries,apple young fruits,acorns,prickly pears,papaya skins,grape seeds and hawthorn are considered relatively high-quality phenolic raw materials.（2）Research on the physical and chemical properties of the 16 phenolic extracts selected,found that hawthorn,T4,apple young fruit,acorn,oak,T6,T3 and pomegranate peel polyphenol extracts had higher total phenol content than others;apple young fruits,grape seed,T2,green tea,green tea,grape skin and T6 polyphenol extracts had higher total flavanol content than others;the five polyphenol extract of pomegranate,chestnut,oak,TI and raspberry had higher ellagitannin content;the polyphenol protein with higher ellagitannin content had stronger binding capacity;the ability of phenolic substances to precipitate proteins was related to the total phenol content,and substances with high total phenol content had strong protein precipitation ability.（3）22 kinds of phenolic extracts were added to white wine to observe their influence on wine color.The wine has been oxidized during storage.With the extension of time,the total flavanol content of Chardonnay wine showed a decreasing trend;as the aging time increases,the L*value of wine showed a trend of first increasing and then decreasing.The a*value and b*of wine samples showed an overall upward trend.T4,T3,chestnut shell,young apple,mint leaves,roxburgh pear and papaya can inhibit the rise of red value.The addition of 50 mg/L chestnut shell polyphenol extract had the most obvious inhibitory effect on the increase of red value.Mint leaf,chestnut shell,roxburgh rose,acorn,sorghum shell,black tea,apple fruit,oak polyphenols extract can inhibit the yellow value.The addition of 50 mg/L chestnut shell polyphenol and 75 mg/L sorghum shell extract had the most obvious inhibitory effect on the increase of yellow value.（4）22 kinds of phenolic extracts were added to red wine to observe their influence on wine astringency.During the wine ageing,the content of total phenols and total flavanols of red wine showed a downward trend.As time goes by,the astringency of the wine was only slightly reduced.The addition of exogenous tannins does not change the trend of the astringency of Pinot Noir wine;Four exogenous tannins,T2,T6,green tea and grape seed,made the wine slightly more astringent than the others...