The Wine Making Environment Adaptability Of Glycosidase From Selected Non-saccharomyses And Its Mix-fermentation

Aroma compounds in grape berries mainly exist as glycosidic aroma precursors which produce aroma characteristics by hydrolysis through releasing volatile compounds during the winemaking process.The free aroma compounds can impart typical and complex aroma characteristics to wine.It is important to note that the key enzyme for enzymolysis is?-D-glucosidase.Some ?-D-glucosidase from non-Saccharomyces yeasts has higher activity and tolerance than from Saccharomyces cerevisiae in wine making environment.Therefore,glycosidic aroma precursors can be hydrolyzed efficiently,which give a significant contribution to enhance the quality of wine aroma.In this study,some non-Saccharomyces strains with higher?-D-glucosidase activity were selected from liquor cellar and the wine making environment,and the wine making environment adaptability of these five glycosidases,include ?-D-glucosidase,?-L-arabinosidase,?-L-rhamnosidase,?-D-xylosidase,?-D-galactosidase,were studied.The potential of selected non-Saccharomyces yeasts were evaluated during the fermentation mixed with commercial S.cerevisiae yeast.The main results are as follows:(1)The wine making environment adaptability of glycosidases from five non-Saccharomyces and the storage stability of their ?-D-glucosidase.The non-Saccharomyces tested were Rhodotorula mucilaginosa,Hanseniaspora uvarum,Pichia membranefaciens and three strains of Lodderomyces elongisporus.Compared with S.cerevisiae,the activities of?-D-glucosidase in glycosidase extract from strains tested were 26.49 mU·mL-1,19.67 mU·mL-1,17.41 mU·mL-1,34.00 mU·mL-1,27.62 mU·m L-1,29.83 mU·mL-1,and S.cerevisiae was 19.40mU·mL-1,respectively.Besides,the activities of ?-L-arabinosidase,?-L-rhamnosidase,?-D-xylosidase,?-D-galactosidase were different in different yeast strains.The optimum temperature of these five glycosidases from strains tested was between 40? and 60?,and the optimum pH was between 5.0 and 6.0.Higher concentrations of glucose and ethanol had an negative effect on glycosidase activities.Among these glycosidases,the ?-D-glucosidase was significantly effected by temperature,pH,and glucose,especially the enzyme from S.cerevisiae.Compared with ?-D-glucosidase,the tolerance of the other four glycosidases was relatively stronger.The ?-D-glucosidase from the enzyme extract had stronger stability under 20? in the short time storage than the long-term storage.(2)The activities of glycosidases during the alcohol fermentation in the same proportion.The ?-D-galactosidase activity was highest in the mixed fermentation of S.cerevisiae and non-Saccharomyces in the proportion of 1:1 and the gingle S.cerevisiae fermentation.The activities of ?-L-rhamnosidase and ?-D-xylosidase from the wine treated by the mix fermentation were higher than from the gingle S.cerevisiae fermentation during the whole fermentation.Besides,the activities of ?-D-glucosidaseand and ?-L-arabinosidase were higher in the mix fermentation than in the gingle S.cerevisiae fermentation during the early stage of fermentation(the first 8 days),and then became lower.(3)The evaluation of mix-fermentation by selected non-Saccharomyces and S.cerevisiae.The concentratiion of volatile aroma compounds of the wine samples was analyzed by the solid-phase microextraction and gas-chromatography mass spectrometry(SPME-GC-MS)and the sensorial analysis.The mixed fermentation effectively increased the concentration of varietal aroma compounds,such as ?-damascenone,hotrienol,linalool,and their concentration increased with higher inoculation ratio of L.elongisporus.Moreover,the mixed fermentation significantly enhanced the total concentration of fermentation aroma compounds,such as acetate esters,C6-C12 fatty acid ethyl esters,phenylethyls,fatty acids.The mixed fermentation had an limited effect on the concentration of higher alcohols.Sensory analysis showed that the mixed fermentation increased the complexity and intensity of wine aroma,which increased the aroma of citrus and small berries significantly,especially in the higher proportion of non-Saccharomyces treated wines,and the mixed fermentation increased sweet fruit,fruit and flowers flavor.However,it also improved the green characteristic.