Decoding the Specific Roasty Aroma Wuyi Rock Tea (Camellia sinensis: Dahongpao) by the Sensomics Approach

Abstract

Aroma extract dilution analysis was performed on volatile fractions extracted from a freshly prepared Dahongpao (DHP) tea infusion using solvent-assisted flavor evaporation, yielding 65 odor-active domains with flavor dilution factors ranging between 32 and 32,768. In addition, six aromatic substances were captured by headspace analysis. Quantitation of 54 compounds by an internal standard method and stable isotope dilution assays revealed that the concentrations of 32 odorants exceeded their respective orthonasal odor threshold values in tea infusion. The results of odor activity values (OAVs) suggested that 2-metylbutanal (malty) and γ-hexalactone (coconut-like) had the highest OAVs (248 and 154). Eight odorants including γ-hexalactone (OAV 154), methyl 2-methylbutanoate (59), phenylacetic acid (7.2), acetylpyrazine (5.7), 2-methoxyphenol (3.4), p-cresol (2.7), 2,6-diethylpyrazine (2.7), and vanillin (1.8) were newly identified as key odorants in DHP tea infusion. An aroma recombination model in a non-volatile matrix extracted from tea infusion satisfactorily mimicked the overall aroma of DHP tea infusion, thereby confirming the identification and quantitative experiments. Omission experiments verified the obvious significance of 6-methyl-5-hepten-2-one (OAV 91), 2-ethyl-3,5-dimethylpyrazine (19), 4-hydroxy-2,5-dimethylfuran-3­(2H)-one (13), and acetylpyrazine (5.7) as key odorants for the special roasty and caramel-like aroma of DHP tea.

Insights into Characteristic Volatiles in Wuyi Rock Teas with Different Cultivars by Chemometrics and Gas Chromatography Olfactometry/Mass Spectrometry

“…Methyl salicylate and p -cymene are common aromatic VFCs in teas, which are derived from the biosynthesis of the shikimate pathway in tea plants [ 34 , 35 ], and the free form of methyl salicylate is released via the hydrolysis of their glycosidically bound forms under enzymatic or thermal reactions during tea processing [ 36 ]. In addition, methyl salicylate has been reported to be one of the odorants in DHP, but its contribution to the overall aroma is far less than that in this study [ 17 ]. The differences in extraction and detection methods may be the main reasons for the differences.…”

“…These compounds may be potential odorants that reflect the aroma characteristics of WRTs from different cultivars. 2-Methyl-3,5-diethylpyrazine has been proven to be the key odorant responsible for the special roasted and caramel-like aroma of DHP tea [ 17 ]. Coumarin has been reported as the odorant of Jingshan cha and Longjing green teas [ 32 , 33 ], while it was firstly recognized as the aroma-active compound in oolong teas.…”

“…In addition, a comparison of the aroma profiles of WRTs in the same growing regions (northern Fujian) with similar cultivars has rarely been reported. Moreover, the aroma-active compounds in the different WRTs are mainly determined by the assessment of the odor activity value (OAV) [ 14 , 15 ], while the direct contribution evaluation of each volatile in WRTs with similar cultivars by gas chromatography olfactometry (GC-O) is rarely performed, which has been regarded as an intuitive and essential technology in the flavor analysis of foods [ 16 , 17 , 18 ].…”

Variation in Volatile Compounds of Raw Pu-Erh Tea upon Steeping Process by Gas Chromatography–Ion Mobility Spectrometry and Characterization of the Aroma-Active Compounds in Tea Infusion Using Gas Chromatography–Olfactometry–Mass Spectrometry

“…To obtain accurate quantitative data for aroma-active compounds, the internal standard (1,2-dichlorobenzene) and standard substances of aroma-active compounds identified by the SBSE (or HS-SPME/SAFE) were mixed and diluted in a gradient of concentrations (0.001–0.3 μg/kg) of dichloromethane according to five concentration ratios (1:3, 1:9, 1:27, 1:81, and 1:243). Then, the mixed solutions were analyzed by the corresponding methods for the determination of the concentration according to the calibration curve equation …”

“…Then, the mixed solutions were analyzed by the corresponding methods for the determination of the concentration according to the calibration curve equation. 49 Odor Activity Values (OAVs) and Aroma Recombination/ Omission Experiments. OAV was applied to evaluate the contributions of the RAPT infusion aroma compounds (the ratio of the concentration divided by the respective odor threshold).…”