Different influences of β-glucosidases on volatile compounds and anthocyanins of Cabernet Gernischt and possible reason.

The effects of three β-glucosidases (BG1, BG2 from Trichosporon asahii, AS from Aspergillus Niger) on the aroma profiles of Cabernet Gernischt (CG) were investigated, coupled with an exploration of the possible reasons for the different performances of β-glucosidases under the two different conditions (hydrolysis of grape glycoside extract and wine-making). The analysis of headspace solid-phase micro-extraction and gas chromatography-mass spectrometry revealed that volatile flavour compounds in the β-glucosidase-treated samples were significantly increased. Specially, the wines treated with β-glucosidase BG1 occupied the highest concentrations of 19 out of 23 volatile compounds that exhibited significant differences. The investigation of the effects of pH or glucose on β-glucosidases showed that low pH is the main factor that exerts a more critical and irreversible influence on the activities and structures of β-glucosidase proteins. The stronger resistances to pH and glucose provided β-glucosidase BG1 a better ability in hydrolysing aromatic precursors than other enzymes under winemaking conditions. With the HPLC analysis, eight anthocyanins were identified from CG wine. Among the three β-glucosidases, BG1 showed the lowest influence on the main anthocyanin glycosides. These results suggested that the β-glucosidase BG1 may have some potential values to complement wine quality during the winemaking process.