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Aims: The purpose of the study was to evaluate the effect of b-glycosidase activity in wine yeasts in releasing terpene glycosides from grape juice. Methods and Results: Glycosidase activity was screened in 160 yeasts by testing their ability to hydrolyse arbutine on agar plates. Only non-Saccharomyces species exhibited b-glycosidase activity. Enzyme activity, based on hydrolytic activity on p-nitrophenyl-b-glycoside, was mainly located in the whole cell fraction, with smaller amounts in permeabilized cells being released into the growth medium. The hydrolysis of glycosides was determined by HRGC-MS, con®rming the role of yeast in the liberation of monoterpenols, especially linalool and geraniol. Conclusions:The results indicate the potential of microbial b-glycosidases for releasinḡ avour compounds from glycosidically-bound, non-volatile precursors, with signi®cant implications for wines made from less aromatic grapes. Signi®cance and Impact of the Study: This study con®rms the role of non-Saccharomyces species in enhancing wine aroma and¯avour, suggesting that the future lies with controlled use of mixed cultures in winemaking.

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The gas chromatography-olfactometry (GC-O) methods, detection frequency and posterior intensity, were evaluated to determine the odour intensity of three Aragonez clonal red wines. An experienced panel of eight sniffers was used and 36 odorant compounds were detected. Positive significant correlations were obtained between detection frequency and average intensity scores. Principal component analysis of the scores obtained by the posterior intensity method revealed a good separation among the three Aragonez clonal red wines. Clonal wine A1 presented the highest odour intensities. Indeed, this wine was highly influenced by several odorant compounds, in particular, varietal compounds such as β β β β β -damascenone and 2,5-dimethyl-4-hydroxy-3(2H)-furanone. These results pointed to the posterior intensity method as a suitable tool for clonal red wines differentiation.

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Odorant compounds of five young clonal red wines made from cv. Trincadeira, a native grape variety of Vitis vinifera L. grown in Portugal, were studied using 2001 and 2003 vintages. The study was carried out using gas chromatography-mass spectrometry (GC-MS) for compound identification and the gas chromatography-olfactometry (GC-O) posterior intensity method to detect the potentially most important aroma compounds. Forty-one odorant peaks were detected by GC-O analysis, from which 31 were identified by GC-MS. The odorant compounds with the highest odorant average intensities are 3-methylbutanoic acid, 2-phenylethanol, 2,5-dimethyl-4-hydroxy-3(2H)-furanone, and 4-vinylguaiacol. The GC-O analysis showed odor intensity differences among compounds, which was confirmed by analysis of variance (ANOVA). Principal component analysis (PCA) and hierarchical cluster analysis (HCA) showed that the five clonal wines from the 2001 vintage were more similar than those from the 2003 vintage. Moreover, stepwise linear discriminant analysis (SLDA) demonstrated that the factor vintage has influence on the Trincadeira clonal red wine odorant profile differentiation.