Abstract:

This study aimed to optimize the conditions for shortening the time required to brew green tea in water at room
temperature and simultaneously obtaining quality tea infusion with ultrasound assistance. A comparison with the standard
boiling water brewing method was carried out by measuring quality parameters of tea infusions. A tea-to-water ratio of
1:30 (g/mL) and 10 min ultrasound treatment proved optimal. The content of water extracts in tea and the concentrations
of tea polyphenolics and caffeine in tea infusion were lower under these conditions than those obtained with the standard
boiling water brewing method, whereas total free amino acid levels were achieved by the proposed method. The aroma
components from the two brewing methods were substantially identical. However, the tea brewed at room temperature
lacked those substances having unpleasant fat odor, such as octanal and (E)-2-octenal but contained increased levels of
delicate fragrance substances including alpha-linalool and trans-2-hexenyl caproate. This study provides a preliminary
confirmation of the feasibility of ultrasonic-assisted green tea brewing at room temperature, which produces a refreshing
and mellow taste and a delicate and long-lasting aroma indicating better overall sensory quality than boiling water brewing.
These results indicate that the ultrasound-assisted method is particularly suitable for industrial extraction of tea and can
greatly save energy and reduce emissions.

Key words: green tea, ultrasound-assisted method, brewing at room temperature, condition, quality