Comparison of Aroma-Active Volatiles in Oolong Tea Infusions Using GC–Olfactometry, GC–FPD, and GC–MS

Abstract

The aroma profile of oolong tea infusions (Dongdingwulong, DDWL; Tieguanyin, TGY; Dahongpao, DHP) were investigated in this study. Gas chromatography-olfactometry (GC-O) with the method of aroma intensity (AI) was employed to investigate the aroma-active compounds in tea infusions. The results presented forty-three, forty-five, and forty-eight aroma-active compounds in the TGY, DHP, and DDWL infusions, including six, seven, and five sulfur compounds, respectively. In addition, the concentration of volatile compounds in the tea infusions was further quantitated by solid phase microextraction-gas chromatography (SPME)-GC-MS and SPME-GC-flame photometric detection (FPD). Totally, seventy-six and thirteen volatile and sulfur compounds were detected in three types of tea infusions, respectively. Quantitative results showed that forty-seven aroma compounds were at concentrations higher than their corresponding odor thresholds. On the basis of the odor activity values (OAVs), 2-methylpropanal (OAV: 230-455), 3-methylbutanal (1-353), 2-methylbutanal (34-68), nerolidol (108-184), (E)-2-heptenal (148-294), hexanal (134-230), octanal (28-131), β-damascenone (29-59), indole (96-138), 6-methyl-5-hepten-2-one (34-67), (R)-(-)-linalool (63-87), and dimethyl sulfide (7-1320) presented relatively higher OAVs than those of other compounds, indicating the importance of these compounds in the overall aroma of tea infusions.

Identification of key aromatic compounds in Congou black tea by partial least‐square regression with variable importance of projection scores and gas chromatography–mass spectrometry/gas chromatography–olfactometry

“…The fourth pathway, glycol, is the hydrolyzation of glycosides, which releases glycosidically bound volatiles during the fermentation process, such as geraniol, linalool, and linalool oxides, aromatic alcohol aglycones of benzyl alcohol, and 2‐phenylethanol . These volatiles are considered as the characteristic aroma components of black tea, oolong tea, and green tea …”

“…2‐Hexenal, 3‐hexenol, ethylpyrazine, geraniol, linalool, ( Z / E )‐linalool oxides, ( E / Z )‐2,6‐nonadienal, phenylethanol, β ‐ionone, hotrienol, and dihydroactinidiolide were identified to be odour‐active components of Kangra orthodox black tea . Such effective approaches have been successfully applied to a variety of foods, such as cranberry, mandarins, Pontianak orange peel oil, green tea, and oolong tea …”

Characterization of aromas of instant oolong tea and its counterparts treated with two crude enzymes from Aspergillus niger

“…This phenomenon was consistent with a previous study that the chemicals such as nerolidol and phenyl acetaldehyde were the characteristic aroma compounds of Oolong tea (Wang et al, ). Besides, the OIOT showed higher OAVs of β ‐trans‐ damascenone (OAVs of 22,543.7 vs. 0.0) and octanal (OAVs of 59,529.0 vs. 31,294.1) than the NIOT (Table ), which might explain why the OIOT had much stronger intensities of sweet and fruit notes (Table ), since these chemicals possess honey‐like and fruity notes (Zhu et al, ). In addition, the OIOT had lower OAVs of 2 ‐ pentyl‐furan, trans‐ nerolidol, phenyl acetaldehyde, and hexanal than NIOT, which might explain that the OIOT had weaker grass and floral notes and lower aroma acceptance (Table ), because these volatiles possess grass or floral notes (Qin et al, ).…”

“…The two compounds contributed to the majority of the total OAVs of the EWBOP‐OIOT. β‐ trans‐ Damascenone and octanal have been reported to present honey‐like and orange‐like odors (Zhu et al, ), respectively. Thus, these two volatile chemicals are considered the main contributors to the strong sweet and fruity notes of the EWBOP‐OIOT.…”

“…Afterward, the odor activity value (OAV) was calculated by dividing the concentration of a volatile with its corresponding odor threshold in water obtained from previous researchers. (Birch, Petersen, Arneborg, & Hansen, ; Giri, Osako, Okamoto, & Ohshima, ; Joshi & Gulati, ; Ni, Chen, et al, ; Ni, Hong, et al, ; Qin, Ma, Wu, Shan, & Ren, ; Ravichandran & Parthiban, ; Schuh & Schieberle, ; Tønder, Petersen, Poll, & Olsen, ; Yang et al, ; Zhang, Li, Qi, & Wan, ; Zhu et al, ).…”