Study On The Regulation Of Aroma Of Cabernet Sauvignon Dry Red Wine From Eastern Foothill Of Helan Mountain By Micro-oxygenation Processing

The integrated quality of Cabernet Sauvignon dry red wine from Eastern Foothill of Helan Mountain in Ningxia is good.The new wine is of rich aroma,but its aroma weakens quickly during aging,leading to poor senses of hierarchy and typicality.Micro-oxygenation(MOX)technique has been widely applied in many other wine regions,and it can improve aroma quality of wine.However,MOX has not been used effectively in Eastern Foothill of Helan Mountain wine region,and the effects of MOX on wine aroma of this region are rarely reported.In this paper,the MOX processing of Cabernet Sauvignon dry red wine from Eastern Foothill of Helan Mountain was studied,the main affecting factors of MOX treatment were analyzed and compared,and the formation mechanisms of key aroma compounds were preliminarily explored,to systematically explain the regulation mechanism of wine aroma by MOX.The main results are as follows:(1)Effects of MOX on aroma compounds and aroma characteristics of wine.The effects of different periods and different levels of MOX treatments on concentrations of fatty alcohols,benzyl alcohol,methyl ester,ethyl esters,isopentyl esters,acetates,lactone,aliphatic aldehyde,and terpenes varied among different wines,while different MOX treatments could uniformly increase concentrations of 2-phenylethanol,benzaldehyde,diacetyl and 2,3-pentanedione of all the wines.For wine with relatively poor quality,the effects of MOX on aroma compounds were more obvious.MOX was able to improve aroma quality of wine,by reducing green and animal notes,and enhancing notes of dried fruits,flowers and nuts.Among them,the enhancement of floral flavor was related to the increase of 2-phenylethanol,and the enhancement of nutty flavor was related to the increase of benzaldehyde and diacetyl.(2)Effects of pH,free SO2(FSO2),total phenols(TP)and Fe2+on the regulation of wine aroma by MOX.The higher the pH/FSO2/Fe2+,the faster/more the wine consumed oxygen.During MOX,the oxidation-reduction potentials of most wines were increasing to varying degrees,except for wines of pH 4.0 and TP 4.4 g/L.During MOX,lower pH(3.2)could promote the formation of 2-phenylethanol and slow down the oxidation of esters,while higher FSO2(40 mg/L)and TP(4.4 g/L)could not protect esters and terpenes very well,and wine with Fe2+content higher than 2.5 mg/L was more likely to be oxidized excessively.Based on the analysis of aroma compounds,for wine undergoing MOX,its pH should be lower than 3.6,Fe2+ content should be lower than 2.5 mg/L,and its FSO2 and TP content ought to be controlled within reasonable ranges(20?30 mg/L and 2.2?3.3 g/L respectively).(3)The regulatory mechanisms of 2-phenylethanol and benzaldehyde by MOX.Mass fragmentation patterns of molecular ions of 2-phenylethanol,benzaldehyde and benzyl alcohol were analyzed by product ion scan.Collision voltages of MS/MS were optimized.Quantitative methods of multiple reaction monitoring for these three aromatic compounds were established.MOX could promote the phenylpyruvate decarboxylase activity of yeast,which may be one of the main reasons of the increment of 2-phenylethanol.Benzyl alcohol could be oxidized to benzaldehyde by Fenton reaction,which may be one of the main reasons of the increment of benzaldehyde during MOX treatment.