Characterization of bioactive and volatile profiles of thyme (Thymus vulgaris L.) teas as affected by infusion times

摘要

The influence of different infusion times on phenolic, volatile, antioxidant, and colour properties of thyme (Thymus vulgaris L.) teas was investigated in the present study. The thyme teas were prepared using freshly boiled water at infusion times of 0, 2, and 5 min. The effect of infusion time on phenolics, volatiles, and antioxidant properties was clearly observed. Among the phenolic compounds identified in the samples by LC-MS-MS, luteolin-diglucuronide-glucuronide and protocatechuic acid-hexoside were identified for the first time ever in thyme teas, with the most dominant phenolic compound in all samples subsequently being luteolin-diglucuronide-glucuronide. A significant correlation between the phenolic compounds and antioxidant properties demonstrates that phenolic compounds affected the antioxidant potential of the thyme tea infusions. A total of 27 volatile compounds were identified and quantified in the samples. The main chemical group of the volatile compounds in the thyme teas was terpenes and represented almost 90% of the total volatiles in thyme teas. Among the terpenes, thymol (61.74-78.82%), p-cymene (8.92-17.90%) and carvacrol (4.41-5.62%) being the most abundant volatiles in all the teas. Results obtained by sensory evaluation indicate that taste panelists preferred thyme tea prepared at a 0-min infusion time.