Characterizing volatile metabolites in raw Pu'er tea stored in wet-hot or dry-cold environments by performing metabolomic analysis and using the molecular sensory science approach.

The aroma profile of raw pu'er tea (RPT) depends on its storage duration (2-10 years) and storage conditions (wet-hot or dry-cold environment). We analyzed the major odorants of RPT samples by performing metabolomic analysis and by using the molecular sensory science approach. Under dry-cold storage conditions, tea leaves had more carotenoid derivatives, glycoside-derived volatiles, and phenolic volatiles, resulting in "fresh," "floral," and "sweet" aroma. Under wet-hot storage conditions, tea leaves had more methoxybenzenes, which contributed considerably to their "stale" and "woody" aroma. We identified 11 and 4 compounds as the odor markers of RPTs when stored in dry-cold and wet-hot environments, respectively. Our findings provide a scientific basis for optimal storage that yields the desired aroma profile.

[Identification of Pu'er teas with different storage years by FTIR spectroscopy].

Infrared spectra of Pu'er raw tea and Pu'er ripe tea were investigated using Fourier transform spectroscopy, in order to exploit a rapid method for discrimination of aging period for Pu' er tea samples. The results showed that the two kinds of Pu'er teas shared a similar woveform of infrared spectrum. However, due to the variations of aging time, leading to different chemical composition in pu'er teas, both Pu'er raw tea and ripe tea displayed corresponding different characteristic peaks. And the extent of aging of Pu'er tea had a significant relationship with optical density and waveforms of absorption peaks in the wave number range of 1 120-1 570 cm(-1) and 400-853 cm(-1), suggesting that the extent of aging of Pu'er tea may be identified by infrared spectrum technology rapidly and simply.