Method for liquid fermentation of black tea juice by using aged green tea

A method for liquid fermentation of black tea juice by using aged green tea, comprising the following process steps:

• 1) mixing aged green tea with hot water for a water bath-assisted extraction to prepare a crude catechin extract;
• 2) adding a tannase into the crude catechin extract obtained in step 1) for a water bath-assisted enzymolysis to obtain a primarily enzymolyzed crude catechin extract;
• 3) freeze-withering fresh tea leaves;
• 4) homogenizing the freeze-withered leaves obtained in step 3);
• 5) pouring a homogenate obtained in step 4) into the primarily enzymolyzed crude catechin extract, adding a β-glucosidase for secondary enzymolysis and performing fermentation;
• and
• 6) treating a fermentation broth obtained in step 5) by microwave heating, and performing filtration and cooling to a room temperature to obtain black tea juice by liquid fermentation using aged tea.