Evolution Of Aroma Compounds During Winemaking Process Through The Treatment With Glycosidases

The hydrolysis of aroma glycosidic precursors during the winemaking process is a complex process.The aroma glycoside precursors present aroma characteristics by releasing the volatile compounds through appropriate hydrolysis conditions and methods.In this study,wines treated by glycosidases in the process of alcohol fermentation were taken as the objects.Free and bound aroma compounds in wine samples which were collected in sequence were detected to look for the evolution of aroma compounds during the winemaking process and evaluate the potential of the glycosidases from non-Saccharomyces cerevisiae in wine aroma enhancement.The main findings are as follows:(1)The properties of ?-D-glucosidases from selected non-Saccharomyces cerevisiae in the simulated winemaking conditions.The ?-D-glucosidase activity of P.membranifaciens and R.mucilaginosa were 32.29 mU/mL and 26.49 mU/mL,respectively.The enzyme activity was defined as 100% when the glucose content was 0 g/L,the ethanol content was 0%,the pH value was 4.0,the temperature was 40?.The ?-D-glucosidase of R.Mucilaginosa could tolerate lower pH value,lower temperature and higher glucose concentrations.At pH 3.0,the relative activity was above 50%;the relative activity was above 75% in the temperature between 5?and 30?;when the sugar concentration was 300 g/L,the enzyme activity was above 65%.?-D-glucosidase of P.membranifaciens could tolerate high concentrations of ethanol.Its ?-D-glucosidase activity stabilized between 112% and 120% at 10%-15% ethanol concentration.(2)Evolution of aroma components in wine samples treated with glycosidases during the winemaking process.It was found that the concentration of free C6 compounds gradually increased during the whole fermentation process,and the hydrolysis of C6 compounds in the middle of alcohol fermentation was the strongest.The addition of enzyme preparation reduced the concentration of C6 compounds during the alcohol fermentation process.The concentration of terpenols compounds was the highest in alcohol fermentation for 48 h,and the treatment with glycosidases did not significantly increase the concentration of terpenols.C13-Norisoprenoids are mainly formed during the storage,the concentration of the bound aroma compounds is higher than the free during the alcohol fermentation process.Enzymetreatments had less effect on the concentration of C13-Norisoprenoids.The concentration of the free higher alcohols gradually increased during the winemaking process,and it was far more than the bound.Enzyme treatments increased the concentration of higher alcohols during the winemaking process.Apart from higher alcohols,the concentration of fermentative aroma compounds during the winemaking process increased first and then decreased.The concentration of free phenylethyls reached the highest level at the end of alcohol fermentation,and the concentration of bound aroma was less and changeless.Non-S.cerevisiae glycosidase treatments can reduce the production of esters and fatty acids during the winemaking process.(3)Aroma compounds and aroma characteristics in wine samples treated with glycosidases.The sensory analysis of wine samples was conducted by the "sensory quantification method",which combined with the aroma composition to evaluate the application results of glycosidases.In the wine treated without enzymes,the concentration of higher alcohols,C6 compounds,terpenes and fatty acids was higher,which added green,sour fruit,small berries and sweet fruits characteristics.The treatment of P.Membranifaciens glycosidase had obvious floral flavor,which was related to the increase of the concentration of C13-Norisoprenoids.The treatment of R.mucilaginosa glycosidase increased the concentration of fatty acid ethyl ester,aldehydes and ketones,and C13-Norisoprenoids,which could bring tropical fruit,citrus and floral for the wine.The almond ?-glucosidase treatment increased the esters of phenlic acid,acetate esters and phenylethyls compounds,while this wine had more off flavor,for example fungal.