Black teas harvested during the summer season usually have the defect of low aroma intensity, resulting in unacceptability from consumers. The shaking and standing (SS) process is key to the ...production of oolong tea and is believed to significantly improve the aroma quality. However, the specific effects of the shaking process on the aroma quality of black tea have not been elucidated. SSBT has a higher aroma intensity than BT, especially floral and sweet odors. By Aroma Extract Dilution Analysis (AEDA), 27 volatiles with flavor dilution factor (FD) above 8 were selected, of which 20 had odor activity values (OAV) values above 1; among them, 9 floral and sweet volatiles with high OAV were linalool (485 for BT, 918 for SSBT), (E)-β-ionone (389, 699), geraniol (315, 493), β-myrcene (25, 62), (E)-2-hexenal (2, 7), phenylacetaldehyde (44, 75), (Z)-3-hexenyl hexanoate (19, 41), 1-hexanol (9, 26), and 2-phenylethanol (2,3). Aroma reconstitution of these 20 volatiles showed reliable results of floral, sweet, fruity, and roasted odors, further validating the aroma and intensity profiles of the key odorants. Overall, our results reveal that the metabolite mechanism of the SS process improves the aroma quality of black tea, providing a theoretical basis and guiding measures for the production of high-aroma black tea.
•Shaking and standing improve the sweet and floral aroma of black tea.•Volatiles in tea were detected by SPME- and SAFE-GC–MS.•Nine key odorants responsible for sweet and floral aroma were verified.•A novel processing flow for high-quality black tea was proposed.
This study was to understand characteristic aroma properties of kale tea made by roasting kale leaves by profiling its aroma composition and screening its aroma-active compounds. Secondary ...metabolites of glucosinolates such as ally isothiocyanate, 3-butenyl isothiocyanate, 3-methylthiopropyl isothiocyanate, and 5-methylthiazole were the primary aroma compounds of raw kale but were less abundant in kale tea. Dimethyl trisulfide, cyclohex-2-en-1-ol, benzeneacetaldehyde, and 4-vinylguaiacol were quantitatively major aroma compounds in kale tea. Pyrazines, aldehydes, sulfides, and 4-vinylguaiacol were newly produced only in kale tea. In particular, 2-ethyl-6-methylpyrazine exhibiting the highest flavor dilution factor was the most potent aroma-active compound of kale tea, followed by methional, 2-ethyl-5-methylpyrazine, 2,5-dimethylpyrazine, 2,6-dimethylpyrazine, two unknown compounds, dimethyl disulfide, furfural, benzaldehyde, and dimethyl trisulfide. These compounds contributed to roasted, sulfur-like/pungent, and sweet aroma characteristics, which were main aroma properties of kale tea. In addition, (
E
)-hex-2-enal and (
Z
)-hex-3-en-1-ol contributed to the green and grassy aromas of kale tea.
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•The largest contributor to the flavor of fried green onion oil was dimethyl trisulfide.•Furaneol and dimethyl trisulfide were the key aroma compounds in fried green onion ...oil.•Dimethyl disulfide polymerization to produce trisulfide compounds at high temperature.
Green onion (Allium fistulosum L.) is a perennial herb with a characteristic allium aroma. Meanwhile, fried green onion oil has a rich flavor that is popular in traditional Chinese cuisine. In this work, the key aroma components of fried green onion oil were focused via flavoromics analysis. The oil samples had a low score of a green aroma but a high score of salty, greasy aromas. Whereafter, a total of 36 aroma-active substances with flavor dilution (FD) factors ranging from 1 to 6561 were identified in fried green onion oil, while 42 were detected in fried green onion residue with FD factors ranging from 1 to 19683. Additionally, the recombination and omission tests revealed that furaneol, dimethyl trisulfide, allyl methyl trisulfide, (E,E)-2,4-decadienal, etc., were the key aroma compounds in fried green onion oil. Furthermore, the observation of the reaction of thioethers at high temperatures revealed that dimethyl disulfide undergoes polymerization to form dimethyl trisulfide. The research results can provide a theoretical basis for the standardization and industrial production of Chinese cuisine.
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•Contributing volatiles for HX and LX aromas were decoded by GC–MS and GC–IMS.•Differential volatiles among HX, LX, QX were confirmed by VIP of PLS-DA and relative OAV.•Alcohols were ...the main contributing volatiles for floral-like aroma in TH green teas.
Aroma types of green teas associate with their commercial prices and consumer acceptance, mainly including floral-like (HX), chestnut-like (LX), and fresh (QX) aromas. However, the volatile differences and specificities in these aroma types are still unclear. Herein, Taiping Houkui green teas with HX, LX, and QX aromas were processed separately with the same fresh tea leaves. Ninety-four and seventy-eight volatiles were detected and identified by headspace solid-phase microextraction gas chromatography–mass spectrometry (HS–SPME–GC–MS) and headspace gas chromatography–ion mobility spectrometry (HS–GC–IMS), respectively. Candidate differential volatiles among the tea samples were determined by the variable importance in projection (VIP) of the partial least squares–discriminant analysis (PLS–DA) and were further confirmed by the relative odor activity value (ROAV) and odor description. The volatiles 1-hexanol, linalool oxide (furanoid), linalool, geraniol, (E)-β-ionone, isoamyl acetate, and 2-methylpropanal enriched in HX and contributed to the floral-like aroma, while 3-methylbutanal, 2-ethyl-1-hexanol, indole, β-damascone, and cedrol enriched in LX and contributed to the chestnut-like aroma. This study reveals the specificities and contributions of volatiles in green teas with different aromas, thus providing new insights into the molecular basis of different flavored teas, benefiting for their precision processing and targeted quality control.
This study investigates the accumulation and degradation of aroma molecules released by acid hydrolysis of aroma precursors in winemaking grapes. A first-order kinetics model effectively interprets ...this accumulation, including subsequent degradation. Experimentation at three temperatures categorizes specific grape-derived aroma molecules into three stability-based groups: labile molecules from labile precursors, stable molecules from labile precursors, and stable molecules from stable precursors. While many grape-derived aromas exhibit similar patterns and levels of accumulation across temperatures, reaction rates significantly increase with temperature. The analysis of 12 samples of two grape varieties hydrolyzed at 50 °C for 5 weeks and 75 °C for 24 h confirms that fast hydrolysis accurately replicates varietal and between-sample aroma compositional differences. Moreover, the accumulated levels of 21 relevant grape-derived aromas strongly correlate with those at 50 °C, indicating that fast hydrolysis at 75 °C reliably predicts grape aroma potential.
•Dynamic variations of volatiles and their precursors in fermentation were studied.•Strong fermentation activities also occurred during the rolling step.•GBVs (especially primeverosides) were greatly ...hydrolyzed during fermentation.•Fermentation largely upgrades the ratio of sweet/floral scent to green scent.•AADVs and CDVs promoted formation of sweet/floral odor more than VTs.
The present study aimed to systematically investigate black tea aroma formation during the fermentation period. In total, 158 volatile compounds were identified. Of these, most amino acid-derived volatiles (AADVs) and carotenoid-derived volatiles (CDVs) showed significant increases, while fatty acid-derived volatiles (FADVs) and volatile terpenoids (VTs) displayed diverse changes during the fermentation period. During this time, fatty acids, amino acids, carotenoids, and glycosidically bound volatiles (GBVs, especially primeverosides) were found to degrade to form aroma components. Further, equivalent quantification of aroma showed that the intensity of green scent was notably decreased, while the intensities of sweet and floral/fruity scents were greatly increased and gradually dominated the aroma of tea leaves. AADVs and CDVs were shown to make greater contributions to the formation of sweet and floral/fruity scents than VTs. Our study provides a detailed characterization of the formation of sweet and floral/fruity aromas in black tea during the fermentation period.
The key odorants of tartary buckwheat (TB) were researched by a sensory-directed flavor analysis approach for the first time. After the volatiles of TB were isolated by solvent-assisted flavor ...evaporation (SAFE), 49 aroma-active components with flavor dilution (FD) factors in the range of 1–2187 were identified using gas chromatography–olfactometry–mass spectrometry (GC-O-MS) combined with aroma extract dilution analysis (AEDA). Geranylacetone, phenethyl alcohol, and β-damascone showed the highest FD factors of 2187. All 49 odorants were further quantitated by the internal standard curve method, and their odor activity values (OAVs) were obtained. The overall aroma of TB was successfully simulated (similarity > 98.16%) by mixing 16 odorants (OAV ≥ 1) with their natural concentrations. The omission tests revealed that geosmin, α-isomethylionone, α-methylionone, β-ionone, linalool, β-damascone, geranylacetone, guaiacol, ethyl hexanoate, geraniol, vanillin, tetrahydrolinalool, and 2,5-dimethyl-4-hydroxy-3-(2H)-furanone were the key odorants of TB. Chiral analysis showed that tetrahydrolinalool and linalool existed as racemics in the commercial TB. The relative content of R-enantiomers of α-isomethylionone and α-methylionone was slightly higher than that of their S-enantiomers. The odor thresholds of R- and S-enantiomer of tetrahydrolinalool were first detected as 0.029 and 3.8 μg/L in air, respectively.
