Effects of ultrasonic-assisted extraction on bioactive compounds, volatile flavors and antioxidant activities of vine tea water extracts.

Background: Ampelopsis grossedentata, vine tea, which is the tea alternative beverages in China. In vine tea processing, a large amount of broken tea is produced, which has low commercial value. Methods: This study investigates the influence of different extraction methods (room temperature water extraction, boiling water extraction, ultrasonic-assisted room temperature water extraction, and ultrasonic-assisted boiling water extraction, referred to as room temperature water extraction (RE), boiling water extraction (BE), ultrasonic assistance at room temperature water extraction (URE), and ultrasonic assistance in boiling water extraction (UBE)) on the yield, dihydromyricetin (DMY) content, free amino acid composition, volatile aroma components, and antioxidant properties of vine tea extracts. Results: A notable influence of extraction temperature on the yield of vine tea extracts (P < 0.05), with BE yielding the highest at 43.13 ± 0.26%, higher than that of RE (34.29 ± 0.81%). Ultrasound-assisted extraction significantly increased the DMY content of the extracts (P < 0.05), whereas DMY content in the RE extracts was 59.94 ± 1.70%, that of URE reached 66.14 ± 2.78%. Analysis revealed 17 amino acids, with L-serine and aspartic acid being the most abundant in the extracts, nevertheless ultrasound-assisted extraction reduced total free amino acid content. Gas chromatography-mass spectrometry analysis demonstrated an increase in the diversity and quantity of compounds in the vine tea water extracts obtained through ultrasonic-assisted extraction. Specifically, 69 and 68 volatile compounds were found in URE and UBE extracts, which were higher than the number found in RE and BE extracts. In vitro, antioxidant activity assessments revealed varying antioxidant capacities among different extraction methods, with RE exhibiting the highest DPPH scavenging rate, URE leading in ABTS+ free radical scavenging, and BE demonstrating superior ferric ion reducing antioxidant activity. Conclusion: The findings suggest that extraction methods significantly influence the chemical composition and antioxidant properties of vine tea extracts. Ultrasonic-assisted extraction proved instrumental in elevating the DMY content in vine tea extracts, thereby enriching its flavor profile while maintaining its antioxidant properties. [ABSTRACT FROM AUTHOR]