## 3 Results
### Analysis of Volatile Aroma Compounds in Chardonnay Wines  
Table 2 compares the GC-MS results of volatile aroma components in purified Mg-\(\beta\)gl- and Hu-\(\beta\)gl-treated Chardonnay wines to An-\(\beta\)gl -treated and naturally aged wines. In this study, the activity of Mg-\(\beta\)gl and Hu-\(\beta\)gl released similar but low amounts of total terpenoids (0.033 mg/L and 0.034 mg/L, respectively) than the commercial enzyme An-\(\beta\)gl (0.039 mg/L). However, both enzymes significantly increased the concentration of volatiles in their treated wines compared with wines without \(\beta\)-glucosidase adding (CK). Between An-\(\beta\)gl-treated wines and purified Mg-\(\beta\)gl- and Hu-\(\beta\)gl-treated wines, there was no significant difference in the total terpenoid concentration, but regarding the concentrations of some specific monoterepne aglycones, significant differences were found. In particular, the activity of Mg-\(\beta\)gl and Hu-\(\beta\)gl resulted in significantly higher levels of linalool (0.023 mg/L each) than An-\(\beta\)gl (0.014 mg/L), and a 52% increase compared to CK. The three enzymes had a significant impact on the hydrolysis of glycosidically bound C\({}_{13}\)-norisoprenoids, resulting in higher concentrations of volatile aroma compounds than the control wine (CK), in which some volatiles were not detected. It is worth mentioning that the activity of An-\(\beta\)gl (0.034 mg/L) resulted in significantly higher total C\({}_{13}\)-norisoprenoids concentration (0.034 mg/L) than Mg-\(\beta\)gl and Hu-\(\beta\)gl (0.016 mg/L and 0.026 mg/L), and that geranyl acetone was only detected in An-\(\beta\)gl-treated wines. For C\({}_{6}\) compounds, the lowest total concentrations were found in An-\(\beta\)gl-treated wines, while the activity of Hu-\(\beta\)gl resulted in the highest total concentrations of C\({}_{6}\) compounds. Interestingly, hexanol showed the highest concentrations in Mg-\(\beta\)gl and Hu-\(\beta\)gl treatments, revealing the important role of \(\beta\)-glucosidase in hydrolyzing hexanol precursors. Thus, Mg-\(\beta\)gl and Hu-\(\beta\)gl were with a preference for hexanol and showed the highest concentrations, indicating the importance of _M. guilliernondii_ NM218 and _H. warum_ BF345 for \(\beta\)-glucosidase in hydrolyzing hexanol precursors. Figure 3: Effect of ethanol concentration on purified enzyme Mg-\(\beta\)gl and Hu-\(\beta\)gl. The values represent the mean of three replicate determinations. The error bars represent SD. After enzymatic treatments, the activity of Mg-\(\beta\)gl and Hu-\(\beta\)gl resulted in an increase in the total concentration of alcohols, esters, and fatty acids compared to CK, which contributed to the improvement of the aromatic complexity of the wines. Moreover, An-\(\beta\)gl treatment resulted in significantly lower total alcohols and esters but with remarkably higher total fatty acids compared with other treatments (Table 2). The alcohols were characterized by \"vegetal\" and \"herbal\" aromas. Among the alcohols, 2-phenylethanol showed the highest increase in Mg-\(\beta\)gl- and Hu-\(\beta\)gl-treated wines. The activity of Mg-\(\beta\)gl and Hu-\(\beta\)gl increased the concentration of 2-phenylethanol by 84% and 78%, respectively, compared to the control (CK). In addition, the significant increase in many esters (i.e., phenethyl acetate, ethyl octanoate, and ethyl heptanoate) in Mg-\(\beta\)gl- and Hu-\(\beta\)gl-treated wines suggests that \(\beta\)-glucosidase from _M. guilliermondii_ NM218 and _H. uvarum_ BF345 have a preference for their precursors. As a point of interest, the enzymatic activity of Hu-\(\beta\)gl increased the concentrations of ethyl octanoate, ethyl heptanoate, and ethyl caprate by 58%, 60%, and 72%, respectively, compared to the control (Table 2), which are known to impart floral and fruity aromas to wine and may positively contribute these to the aroma profile of the wines.