Enzymatic hydrolysis and auto-isomerization during β-glucosidase treatment improve the aroma of instant white tea infusion.

The aroma changes in instant white tea resulting from β-glucosidase treatment was investigated by quantitative descriptive analysis (QDA), gas chromatography-mass spectrometry (GC-MS), odour activity value analysis (OAV), aroma reconstruction and omission tests. The grassy, floral and sweet notes increased significantly (P < 0.05), and the roasted note decreased significantly (P < 0.05) upon β-glucosidase treatment. Quantitative analysis showed that the concentrations of benzaldehyde, benzeneacetaldehyde, (Z)-3-hexen-1-ol, linalool, phenylethyl alcohol, cis-linalool oxide, trans-linalool oxide, hexanol, hotrienol and (E)-2-hexen-1-ol increased significantly (P < 0.05) after treatment; however, (Z)-3-hexen-1-ol isomerized to (E)-2-hexen-1-ol. OAV analysis, aroma reconstruction and the omission test showed that the grassy, floral and sweet notes increased as the (Z)-3-hexen-1-ol, cis/trans-linalool oxide and benzeneacetaldehyde increased, whereas the roasted note declined under the same conditions. The enzymatic hydrolysis of glycosidic precursors and the auto-isomerization of volatile compounds provide new information for understanding how β-glucosidase treatment improves the aroma of tea products.