Abstract:[Objective] This study aimed to prepare cold extracted green tea with good sensory quality and health functions. [Method] The physicochemical and flavor characteristics of cold extracted green tea prepared through ultrasound-stirring-assisted cold brewing were compared with those of green tea prepared through conventional hot brewing and conventional cold brewing. [Result] Ultrasound-stirring-assisted cold brewing promoted the dissolution of polyphenols and free amino acids (especially theanine), and the tea infusion had a phenol-ammonia ratio (1.33) comparable to that of conventional cold brewed tea. In addition, this process significantly enhanced the antioxidant capacity of cold extracted green tea, which showed the ABTS + and DPPH radical scavenging rate of (72.07±3.04)% and (49.54±1.59)%, respectively. Determination of volatile components revealed that the ultrasound-stirring-assisted cold brewing process improved the dissolution of aldehydes, ketones, and esters in the tea infusion, which showed a strong aroma. The OPLS-DA model analysis showed significant differences in volatile components between tea infusions brewed with the three methods, and 35 differential compounds with VIP>1 were screened out. Ultrasound-stirring-assisted cold brewing better retained the original freshness and aroma of green tea than conventional hot brewing and endowed the tea infusion with richer aroma compounds than conventional cold brewing. The OAV analysis showed that ultrasound-stirring-assisted cold brewing retained the characteristic aroma attributes of the tea infusion prepared through conventional cold brewing and enhanced the aroma perception of 1-octen-3-ol, nonanal, and 1-octanol, which showed the OAV values of 5.51, 3.76, and 1.52, respectively. The results of sensory evaluation showed that the tea infusion prepared through ultrasound-stirring-assisted cold brewing had the green tea aroma characteristics such as grassy, floral, fruity, and baking aromas, with a degree of acceptability. [Conclusion] Ultrasonic-stirring-assisted cold brewing has the potential to prepare high-quality cold extracted green tea, which can provide process guidance for the quality improvement of cold extracted tea.
