The Mechanism Of Methanol Formation In Peach Wine And Its Influencing Factors

In this experiment,the structural characteristics and composition changes,pectin content and pectinase activity of peach pectin were studied during the ripening process,combining the methanol content in peach wine at different maturity stages,to explore the formation mechanism of methanol and the effect of pectinase and pectin content on methanol in peach wine.Using 5 different peach juice pretreatment(cooking treatment,clear juice treatment,pectinase treatment,etc.),and measuring methanol content and aroma in peach fermented wine,in order to verify the pectin content and pectinase activity in the fruit to methanol production.And find ways to reduce the methanol content of peach wine.The aim is to clarify the mechanism and influencing factors of methanol production in peach wine,and provide a theoretical basis for further control of methanol content in peach wine.Peach pectin was extracted by ultrasonic assisted extraction and its physical and chemical properties should also be studied.The properties of peach pectin were analyzed by gel permeation chromatography(GPC)and high performance liquid chromatography(HPLC).The molecular weight and composition of Chinese peach pectin were determined at different maturity stages.The results are shown as follows.(1)The content of methanol in peach wine was related to the molecular weight and distribution index of pectin in fruit and the degree of esterification of pectin.The molecular weight and distribution index of pectin in Zhonghua Shoutao fruit were different in different periods.The molecular weight of pectin increased with the maturity of the fruit,and the distribution index decreased.The trend of esterification degree of pectin in the ripening process is consistent with the change trend of methanol content.Combined with the methanol content in peach distilled liquor,if the molecular weight is low,the distribution index is large,then the methanol content in the peach distilled liquor will be low;if the molecular weight is large,and the distribution index is small,then the methanol content in the peach distilled liquor will be high.The degree of esterification of pectin has an effect on the formation of methanol in peach distilled liquor.The higher the degree of esterification of the pectin,the more likely the deesterification reaction to methanol,and the methanol content increases as the degree of esterification of pectin increases.(2)Pectin is a kind of heteropolysaccharide.The main components in theChinese peach pectin are galacturonic acid,arabinose,galactose and rhamnose.The molecular structure of Zhonghua Shoutao Pectin in this experiment is RG-I type,and the decomposition of pectin to produce methanol occurs mainly in the side chain position of the RG-I structure.The changes of peach pectin content and related enzyme activities during ripening and their effects on methanol were analyzed.The results showed that.The content of soluble pectin in peach fruit increased with fruit ripening,and the original pectin content decreased with fruit ripening.The activity of polygalacturonase(PG)in peach fruit decreased first and then increased with fruit ripening,and the pectin esterase(PE)activity showed a decreasing trend as the fruit matured.Correlation analysis showed that the original pectin content,polygalacturonase(PG)activity and pectin esterase(PE)activity in peach fruit were positively correlated with methanol conten.Moreover,the correlation between polygalacturonase(PG)activity and pectin esterase(PE)activity and methanol content in peach wine was higher than that of original pectin content and methanol content.(1)The content of pectin and pectinase activity in the fermented raw materials were changed by pretreatment of peach juice,and the methanol content in peach fermented wine was greatly affected.The pectinase activity in the fermented raw material,caused the highest methanol content in the peach fermented wine,which was1.06 g/L.The pectinase activity in the fermented raw material was mostly inactivated after cooking,which greatly reduced the decomposition of pectin,under this treatment,the methanol content in the peach fermented wine was the lowest,which was 0.53 g/L.After cooking,pectinase was added to the fermented raw material to remove,under the clear juice treatment,the methanol content in the peach wine was also low,which was 0.59 g/L.The effect of pectinase and pectin content on methanol formation was verified.The addition of pectinase can decompose the pectin in the brewing material to form methanol.(2)Peach juice pretreatment affects the type and content of aroma of peach fermented wine.The peach fermented wine in the mixed fermenter has the highest aroma content and the most abundant aroma.The content of alcohols and esters in the fermenter after cooking is significantly reduced,and the content of some phenolic substances(eugenol and 4-methylguaiacol)with aroma of baking is greatly increased.It indicates that the methanol content of the mixed fermentation is high,but the aromasubstance content of the peach fermented wine is the most.(3)Studies have shown that the methanol content in the mixed fermentation is high,but the aroma content of the peach fermented wine is the most abundant.the addition of pectinase will increase the aroma content in the peach fermented wine,but at the same time increase the methanol content in the peach fermented wine.The cooking process will cause the loss of the aroma of the peach fermentation wine but can reduce the methanol content in the peach fermentation wine and increase the baking aroma components in the wine.The clear juice treatment can both reduce the methanol content and retain the flavor substances in the peach wine.