The Characteristics Of Wine-making Tannins And Their Influence On The Astringency Of Red Wines

Red wine astringency is a kind of oral tactile sensation involving drying,roughing,puckering and astringent due to the interaction between tannins and oral cavity,and is also one of the most important factors influencing red wine’s sensory properties and is a key point determining wine’s quality.The intensity of wine astringency is mainly affected by tannin concentration,size and structure.In order to improve the astringency quality of wine,winemakers always add oenological tannins in wine.In this study,The total phenols measurement,total flavanols measurement and high performance liquid chromatography(HPLC)were used to measure the total phenols,total flavanols and flavan-3-nol monomers,mean degree of polymerization(mDP)and tannin activity of oenological tannins.The fluorescent spectroscopy was used to analysis the binding strength of oenological tannin with protein,and the SDS-PAGE was used to analysis the sedimentation ability of oenological tannins to protein.Besides,the effects of oenological tannins on the total phenols,total flavanols and flavan-3-nol monomers,mDP,tannin activity,the binding strength with protein and the sedimentation ability to protein of wine were analysised using the same methods,in order to study the characteristics of oenological tannins and their effects to red wine asreingency.The contents and results of this study are as follows:1.The characteristics of oenological tannins.The total phenols contents of oenological tannins were 297～671mgGAE/g,and the flavanols contents were 0-466mgCTE/g and the mDP of them were 2.7-4.9.The characteristics of oenological tannins was mainly related with their botanical origins.The total phenols,total flavanols,mDP,tannin activity and the sedimentation ability to protein of oenological tannins were the highest,the corresponding parameters of oenological tannins from mixture were lower,the total phenols,tannin activity and the sedimentation ability to protein of oenological tannins from oak or chestnut were lowest,the flavanols of them were not detected,and the mDP of them could not be calculated.The flavan-3-nol monomers of oenological tannins were not related with their their botanical origins and functions.The binding strength with protein of oenological tannins from different botanical origins from strongest to weakest was:green tea mixture,chestnut or oak,grape seeds mixture,grape seeds.The characteristics of oenological tannins was also related with their functions.The total phenols,total flavanols and flavan-3-nol monomers,mDP,tannin activity,the binding strength with protein and the sedimentation ability to protein of tan’cor tannins were higher than VR supra.2.The effects of oenological tannins on red wine astringency.The total phenols content of wine was around 1200mgGAE/L,the total flavanols contents of wine was 600mgCTE/L and the mDP of wine was around 2.2.The total phenols,total flavanols and flavan-3-nol monomers,mDP,tannin activity,the binding strength with protein and the sedimentation ability to protein of wine were advanced after adding oenological tannins.The trends of the related parameters of wine after adding oenological tannins were consistent with that of oenological tannins.3.The characteristics of oaks,grape skins and grape seeds,and their effects on red wine astringency.The total phenols contents of oaks were 2～22mgGAE/g;the total phenols content of grape skins was around 5mgGAE/g,the total flavanols content of grape skins was around 0.06mgCTE/g;the total phenols content of grape seeds was around 10mgGAE/g,the total flavanols content of grape seeds was around 5mgCTE/g.The total phenols of most oaks are higher than that of grape skins and seeds,but the flavanols and flavan-3-nols monomers of them were not detected,and the mDP of them could not be calculated.In the same concentration,the tannin activity and the sedimentation ability to protein of most oaks were weaker than grape skins and seeds,but the binding strength with protein of oaks were stronger than grape skins and seeds.The lighter of the baking degree of oak chips,the total phenols,tannin activity,the binding strength with protein and the sedimentation ability to protein of them were higher.The total phenols,total flavanols and flavan-3-nol monomers,mDP,tannin activity,the binding strength with protein and the sedimentation ability to protein of grape seeds were higher than grape skins.The trends of the parameters of wine after adding oaks,grape skins and grape seeds were consistent with that of oaks,grape skins and grape seeds.