Abstract:

Mulberry leaf tea was prepared by the same procedure as used for green tea and the effects of fixation and airconditioning
treatment on γ-amino butyric acid (GABA) content and quality of mulberry tea were investigated in this study.
The results showed that microwave fixation was better for mulberry tea. After microwave fixation, the leaves were soft and
elastic. The herbaceous smell almost disappeared and delicate fragrance came out because of the microwave processing.
At the same time, the leaves looked verdant and tasted sweet and mellow. The contents of aqueous extracts, soluble sugars
and free amino acids as taste components were 45.78%, 5.68% and 2.83%, respectively, while the contents of functional
components such as GABA, polyphenols and flavonoids were 1.254 mg/g of dry matter, 3.09%, 2.52%, respectively.
When the mulberry tea was processed by microwave fixation combined with air-conditioning treatment including 10%
O2, 80% N2 and 10% CO2, the content of GABA reached the maximum level of 2.275 mg/g of dry matter. The contents of
polyphenols, flavonoids, aqueous extracts, soluble sugars and free amino acids were 3.19%, 2.73%, 44.7%, 5.64% and 2.43%,
respectively. In addition, the last three indicators were at their relatively high levels. It was indicated that the content of
GABA and quality of mulberry tea were both increased by microwave fixation coupled with air-conditioning treatment.

Key words: γ-amino butyric acid, fixation, air-conditioning treatment, mulberry tea