Effect of 1 to 20 years storage on volatiles and aroma of Keemun congou black tea by solvent extraction-solid phase extraction-gas chromatography-mass spectrometry

Abstract Keemun congou black tea (KCBT), a kind of tea suitable for storage, its aroma changes considerably during storage. In this study, seven same grade KCBTs, that had been stored for 1 to 20 years, were analyzed, solvent extraction-solid phase extraction-gas chromatography-mass spectrometry (SE-SPE-GC-MS) was used to analyze volatiles changes. The effect of storage on volatiles was strong, dozens of volatiles varied and had potential to be indicators of storage. In the first category of volatiles, the concentrations fluctuated and then decreased, a clear line of demarcation mostly existed between the 5th and 10th years. In the second category, the concentrations exponentially decreased with a high coefficient of determination (R2) during the entire storage, most of these volatiles were crucial glycoside-derived volatiles, including geraniol, linalool, etc. In the third category, the concentrations increased and then decreased, most of these volatiles were products of the autoxidation of lipids and carotenoids—with hexanoic acid and dihydroactinidiolide being representative examples, respectively. These volatiles were outstanding storage markers for the first 5 years of storage. In the final category, the concentrations continually increased, methoxy benzenes volatiles including 1,2,3-trimethoxybenzene, 1,2,4-trimethoxybenzene etc., were representative and favorable indicators of KCBT being stored for more than 5 years.