Analysis of Heat Release of Key Aroma Substances in Pu-erh Ripe Tea

In this study, the aroma compounds in Pu-erh ripe tea were enriched by means of atmospheric water distillation, and evaluated by gas chromatography-olfactometry (GC-O) after gradient dilution. A total of 22 aroma compounds with flavor dilution (FD) factor log4 equal to or greater than two were identified. Qualitative and quantitative analysis of these aroma compounds was performed using gas chromatography-mass spectrometry (GC-MS), and all of them, with odor activity value (OAV) greater than one, were identified as the key aroma compounds. Qualitative and quantitative analysis of the sequential distillation fractions was carried out using GC-MS, followed by analysis of the release pattern of the key aroma compounds by non-linear fitting model and heatmap cluster analysis. The results showed that the total concentration of key aroma compounds gradually decreased during boiling, and the concentrations of some key aroma compounds such as methoxybenzenes, alcohols and ketones also tended to decrease to different degrees with an increase in water vapor release. But the release pattern of aroma-active aldehydes conformed to the sin function, showing a trend of first increasing, then decreasing and finally increasing again. The concentration of each key aroma compound was analyzed by heatmap cluster analysis; the 22 key aroma compounds were divided into two categories, and the distillation fractions were divided into four categories. The contents of all aroma compounds in the first and second tubes were extremely high. The aroma of the 40th tube was very light with a stronger unpleasant odor, and the contents of most key aroma substances dropped to extremely low levels. This study helps to understand the release pattern of key aroma compounds during the boiling process of Pu-erh ripe tea, and provides a theoretical basis for the recovery and application of aroma compounds from Pu-erh ripe tea.