Effect of β-glucosidase on the aroma of liquid-fermented black tea juice as an ingredient for tea-based beverages

The effects of β-glucosidase on the volatile profiles and aroma stability of black tea juice were evaluated using gas-chromatography-mass spectrometry coupled with sensory analysis. During liquid fermentation of tea leaves, the addition of β-glucosidase increased the concentration of aldehydes, strengthening the undesirable "green grassy" odour. However, the "green grassy" odour was counteracted by adding green tea extract during fermentation. At the same time, "flowery" flavour notes were enhanced, improving the overall aroma quality and strengthening the characteristic "sweet" aroma of black tea. Increased addition of β-glucosidase released more free aroma alcohols from their glucosides. Two "fruity" and "floral" aroma components, benzyl alcohol and phenylethyl alcohol, were not significantly affected by heat treatment (95 °C water bath) and the overall aroma stability was not significantly affected by β-glucosidase treatment. β-Glucosidase treatment improved the aroma, colour and overall suitability of fermented black tea juice as an ingredient for tea-based beverages.