Abstract
The aroma of Keemun black tea (KBT) changes during storage. We investigated key aroma volatiles of fresh KBT (FKBT) and KBT stored for 1 year. Through gas chromatography–olfactometry–mass spectrometry/aroma extract dilution analysis (GC-O-MS/AEDA), 27 aroma volatiles with a flavor dilution (FD) value ≥16 were quantitated. In odor activity value (OAV) analysis, the two samples had nearly the same key aroma volatiles; (Z)-methyl epijasmonate was the exception. Dimethyl sulfide, 3-methylbutanal, 2-methylpropanal, and linalool had especially high OAVs. Except for β-damascenone, volatiles with OAVs > 1 had higher concentrations in FKBT, which revealed that most key aroma compounds were lost during storage. Sweet, malty, floral, and green/grassy aromas corresponded directly to certain compounds. Lastly, the addition test indicated that the addition of several key aroma volatiles decreasing during storage could enhance the freshness of KBT aroma, which may be a potential to control the aroma style of KBT or other teas in industry.
Highlights
fresh KBTs (FKBT) and 1Y-Keemun black tea (KBT) with similar matrices were chosen for this study
GC-O-MS/AEDA and quantitative experiments with FKBT and 1Y-KBT demonstrated that approximately two-thirds of the aroma volatiles were more abundant in FKBT; these included high-volatility compounds, sulfide compounds, and some floral volatiles
One-third of the aroma volatiles were more abundant in 1Y-KBT, including benzeneacetic acid, benzoic acid, and raspberry ketone
Summary
After several months of storage at room temperature, a woody aroma forms and the tea smells notably different from fresh KBTs. Storage has considerable effects on tea aromas. The freshness of the aromas fades and a stale aroma forms after long storage and strongly affects the green tea quality [1]. For an oolong tea such as tieguanyin, several months of room temperature storage can weaken its characteristic lavender aroma but strengthen its grassy aroma. This alteration negatively affects the tea’s quality but the use of vacuum packaging can slow the change. For white teas, an herbal aroma forms during storage that affects the tea positively and storage can strengthen the characteristic stale aroma of dark teas. As far as we know, investigations about the effect of storage on black tea volatiles or odor-active compounds are blank
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