Introduction Tea (Camellia sinensis) is globally consumed for its pleasant flavor, with sweetness being a key factor in evaluating tea quality. While taste compounds contribute to this sweetness, aroma also plays a significant role, but its contribution is not well understood in tea infusion. Objectives This study aimed to identify aroma compounds that enhance sweetness in tea infusion using a sensomics approach, and explore their synergistic effects through molecular docking. Results The aroma increased the sweetness of the tea infusion by more than 24.0 %. Eighteen aroma-active compounds linked to sweetness were identified, among which (E)-β-damascenone (apple-like), linalool (citrus-like), geraniol (citrus-like), dimethyl sulfide (corn-like), (E,E)-2,4-heptadienal (floral), (E,Z)-2,6-nonadienal (cucumber-like), (E)-linalool oxide (furanoid) (floral), dihydroactinidiolide (fruity), γ-nonalactone (coconut-like), and (E)-β-ionone (floral) had higher sweetness similarity and significantly increased the sweet intensity of sucrose (p < 0.05). They likely enhance sweetness by reducing the binding energy of sucrose to sweet taste receptors, forming new hydrogen bonds and hydrophobic interactions. Conclusion This study provides new insights into the role of aroma compounds in tea sweetness and suggests a potential mechanism for their sweetening effect. These compounds could be used as flavour enhancers or additives to improve the sweetness of tea beverages.

Shaking and standing (SS) enhances the aroma intensity and quality of black tea (BT). However, its contribution to the taste remains unknown, and the interaction mechanism between the aroma and taste perception of black tea is also undisclosed. Here, the metabolomics and sensory evaluation-assisted flavor analysis were employed to investigate the changes in non-volatiles induced by SS, and the interaction mechanism between aroma and taste perception. SSBT exhibited considerable reduced bitterness and astringency intensities compared to BT. Notably, the concentrations of contributing compounds such as catechins, proanthocyanidins, theaflavins, anthocyanins, and flavonol glycosides were decreased in SSBT. Sensory experiments further revealed that nine floral and sweet odorants in SSBT exhibited odor-enhancing interactions. Molecular docking validated the binding affinity and interaction forces between mono/di-ligands and OR1G1/OR52D1. Furthermore, the presence of the nine odorants exerted inhibitory effects on the bitterness and astringency of SSBT. These findings provide a novel perspective on the formation of flavor in SSBT.

Drying plays a key role in the formation of the final aroma of black tea. However, the contribution to its aroma remains unclear. Herein, headspace solid-phase microextraction (HP-SPME) and solvent-assisted flavor evaporation (SAFE) coupled with GC-MS were used to detect the volatiles of tea samples (before or after drying) from three cultivars. We found that the drying step caused increase in sweet and fruity aromas and decrease in mintlike and green aromas. 89 Differential volatiles were identified with variable importance in projection (VIP) over 1. Furthermore, 25 decreased aroma-active volatiles were obtained with relative odor activity values (rOAVs) over 1, showing that green, flowery, fruity, sweet, and mint-like decreased significantly by 62.27%, 64.88%, 67.56%, 58.26%, and 69.72% after drying step. (Z)-3-Hexen-1-ol (rOAV = 36.93), linalool (rOAV = 301.56) and methyl salicylate (rOAV = 5.50) were the odorants for the green, flowery, fruity, and mint-like odor. Moreover, other 3 increased aroma-active volatiles showed that flowery, fruity, and sweet volatiles increased significantly after drying step. beta-Damascenone (rOAV = 43.49) was the main odorant for fruity and sweet aroma. The 28 differential volatiles were associated with carotenoid degradation, lipid degradation, and glycoside hydrolysis. This study reveals the contribution of drying to the aroma formation of black tea.

Withering is a crucial process that determines the quality of white tea (WT). Solar withering (SW) is reported to contribute to the aroma quality of WT. However, the mechanism by which aroma is formed in WT subjected to SW remains unclear. In this study, through headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC–MS) and transcriptomics, we found that 13 key genes enriched in the mevalonic acid and methylerythritol phosphate pathways, such as those of 1-deoxy-D-xylulose-5-phosphate synthase and terpineol synthase, were significantly upregulated, promoting the accumulation of α-terpinolene, geraniol, and nerolidol, which imparted floral and fruity odors to WT subjected to SW. Additionally, the significant upregulation of lipoxygenases enriched in the lipoxygenase pathway promoting the accumulation of hexanol, 1-octen-3-ol, (E, Z)-3,6-nonadien-1-ol, and nonanal, which contributed to the green and fresh odor in WT subjected to SW. This study provided the first comprehensive insight into the effect mechanism of SW on aroma formation in WT.

Longjing tea (Camellia sinensis), an iconic agricultural product distinguished by its geographical indication status, has gained much acceptance and consumption in China. The aroma types and steeping conditions of green tea are important factors influencing consumer acceptance. However, the effects of steeping conditions on tea samples with different aroma types are still unknown. Explanation of the above unknowns can provide new insights into the flavor variations of tea when consumed for optimal sensory enjoyment. Here, the aroma profiles of Longjing green teas with bean-like (DX) and fresh aroma (QX) types were analyzed using gas chromatography‒mass spectrometry (GC‒MS), gas chromatography–ion mobility spectrometry (GC‒IMS), and quantitative descriptive analysis (QDA). Geraniol, (E, E)-2,4-heptadienal and other 11 compounds contributed to the bean-like aroma, while heptanal-d, hexanal-d and other 4 compounds contributed to the fresh aroma. Further, the release patterns of volatiles at different steeping temperatures were also revealed. 12 volatiles led to the differences between the two aroma types of Longjing teas at different steeping temperatures. Most volatiles exhibited their aroma characteristics when the steeping temperature exceeded 80 °C. These results enhance the comprehension of green tea's aroma profile, thereby enabling consumers to approach tea drinking from a more scientific perspective.

Piling fermentation (PF) is crucial for Pu-erh tea aroma, yet its microbial and moist-heat impact on aroma quality is poorly understood. Solid-phase microextraction, solvent-assisted flavor evaporation, and gas chromatography–mass spectrometry were used to detected and analyses the samples of sun-green green tea, sterile PF and spontaneous PF. Microbiological action promotes the formation of stale aromas. Moist-heat action promotes the formation of plum-fragrance and sweet aroma. 20 microbial markers and 28 moist-heat markers were screened from 184 volatile components. Combining odor activity values and gas chromatography-olfactometry, 22 aroma-active compounds were screened (1,2,3-trimethoxybenzene, linalool, 1,2,4-trimethoxybenzene …), and analyzed during PF processing. Aroma omission and addition experiments verified its importance. Gallic acid addition experiments successfully verified that microorganisms are the main contributors to the synthesis of methoxybenzenes. Finally, Blastobotrys, Rasamsonia, and Thermomyces showed positive correlation with the synthesis of 1-ethyl-4-methoxybenzene, 1,2,4-trimethoxybenzene, 1,2,3-trimethoxybenzene, and 1,2-dimethoxybenzene. The formation mechanism of Pu-erh tea's aroma was clarified.Exploring microbial and moist-heat effects on Pu-erh tea volatiles and understanding the methoxybenzene formation mechanism using molecular sensory science.

Fixation is a crucial step in the processing of Anjibai tea. In this study, gas chromatography tandem with mass spectrometry was used to analyze the aroma compositions of Anjibai tea across three types of fixation methods: roller-electrical fixation (REF), carding machine fixation (CMF), and roller-hot air fixation (RHF). Nine key volatile compounds were found responsible for Anjibai tea's aroma variations. Results from quantitative descriptive analyses, along with aroma recombination and omission tests, showed that linalool and geraniol significantly contribute to the formation of the medium flowery, fruity, and honey aromas in the REF samples; hexanal has a significant impact on the green aroma in the CMF samples; and 2-ethyl-3,6-dimethylpyrazine is an important aroma compound for the strong roasty aroma in the RHF samples. These findings provide an important theoretical foundation for improving the aroma quality of Anjibai tea and selecting the optimal fixation method.

The harvest date is a crucial factor in determining tea quality. For Lu'an Guapian (LAGP) tea, Grain Rain period (GRP) represents a pivotal phase in the transformation of tea quality. The sensory evaluation, computer vision and E-tongue revealed that the liquor color score, B and G values of tea infusion were increased during GRP, while the astringency, bitterness intensities and the R value of the tea infusion were decreased. Consequently, the tea infusion exhibited a greener hue and the taste became appropriate during GRP. Non-targeted metabolomics revealed that the majority of amino acids and derivatives was reduced during GRP. Furthermore, flavonoids, in particular flavonol glycosides, exhibited considerable variation during GRP. Finally, nine metabolites were identified as markers for quality transformation during GRP by PLS and Random Forest. This study investigated the quality of LAGP teas during GRP and filled the gap in the variation of LAGP tea quality during GRP.

Piling fermentation (PF) is the key to the formation of Pu-erh tea quality; however, the traditional PF process limits the digital and intelligent production of Pu-erh tea. To establish qualitative and quantitative prediction models for the PF degree of Pu-erh tea, hyperspectral imaging technology and chemometric analysis were utilized. A qualitative model that uses least-squares support-vector-machine effectively distinguished the PF degree with an accuracy of 98.63%. Moreover, the chemical contents of quality-affecting components, namely total catechin, free amino acids, and chlorophyll a, were accurately quantified using raw spectral data with residual prediction deviations of 11.26, 4.34, and 3.89, respectively. The spatial distribution of these components during PF was mapped through chemical imaging, and the PF was deemed complete when the model predicted that the total catechin, amino acid and chlorophyll a content were less than 0.48, 11.21 and 1.29 mg/g, respectively. These findings provide a theoretical foundation for digital processing.

To explore the effect of room temperature storage on the flavor quality and biochemical composition of flower and fruit scented black tea,this study compared the sensory flavor quality of flower and fruit scented black tea produced in the years 2019,2020,2021 and 2022 and stored at room temperature,and it detected volatile and non-volatile compounds in the tea by headspace solid-phase microextraction-gas chromatography-mass spectrometry(HS-SPME-GC-MS)and ultra-performance liquid chromatography coupled to orbitrap high resolution mass spectrometry(UPLC-Orbitrap-MS).The results showed that the sensory quality of flower and fruit scented black tea was significantly affected by storage at room temperature,and the tea lost its floral and fruity aroma characteristics after three years of storage at room temperature;its quality characteristic was mature sour taste.The tea samples were divided into four groups of age by principal component analysis(PCA)and hierarchical cluster analysis(HCA).Totally 15 volatile differential compounds such as linalool,cis-β-ocimene,and hexanoic acid(VIP＞1 and P＜0.05),and 154 non-volatile differential compounds such as theanine,epicatechin,and gluconic acid(VIP＞2 and P＜0.05)were selected by partial least squares discriminant analysis(PLS-DA)and one-way analysis of variance(ANOVA).The content of volatile compounds such as linalool,hexanal,cis-β-ocimene,and 2-pentylfuran decreased with increasing storage time,while the contents of hexanoic acid,dihydroactinidolide 1-ethyl-2-formyl-1H-pyrrole,and β-ionone increased.The contents of non-volatile compounds such as most amino acids,nucleotides,sugars,tea polyphenols tended to decrease with increasing storage time,while the contents of organic acids and lipids showed an increasing trend.The results obtained from this study can provide a scientific basis for elucidating the quality changes of flower and fruit scented black tea during storage and help guide its rational storage and scientific consumption.

The quality of crush–tear–curl black tea (CTC-BT) varies greatly by geographic origin. Origin traceability is crucial for consumer interest protection, market order regulation, and food safety monitoring. This paper proposes a fast and accurate method for qualitative discrimination of CTC-BT origins and quantitative detection of its key taste-presenting substances. The method involves a simple colorimetric sensor array and ultraviolet–visible spectroscopy. The effects of various variable screening methods on modeling results were compared. A particle swarm optimization–based support vector machine achieved the highest performance in qualitative discrimination, with a correct classification rate of 99.48%. Based on their origin-distinguishing contributions and dose-over-thresholds, seven key taste-presenting substances were screened, namely, theaflavin, caffine, vitexin-2-O-rhamnoside, rutin, epigallocatechin gallate, epicatechin gallate, gallic acid. A least squares-support vector regression model achieved accurate quantification of the seven aforementioned compounds (square root of determination coefficient of prediction >0.9698, residual prediction deviation >2).

Roasting is a key process in the production of large-leaf yellow tea (LYT) and substantially affects the formation of its aroma. In order to investigate the effect of roasting method on the aroma of large-leaf yellow tea and to identify the potential causes. In this study, guided by molecular sensory science, the aroma components of charcoal-roasted, electric-roasted and drum-roasted LYTs were analyzed using headspace solid phase microextraction and solvent-assisted flavor evaporation in conjunction with gas chromatography-mass spectrometry, and the data were visualized and analyzed using SMICA, SPSS and Origin. The results of quantitative descriptive analysis revealed that rice crust, burnt, corn and floral aromas were significantly different between the three samples. The results of aroma extract dilution and odor activity value analyses revealed that 2,4,5-trimethyloxazole, 1-ethylpyrrole-2-carboxaldehyde, 2-ethyl-3,5-dimethylpyrazine, 3-ethyl-2,5-dimethylpyrazine, linalool, 2,3-diethyl-5-methylpyrazine, 3,5-diethyl-2-methylpyrazine, β-damascenone, and (E)-β-ionone were the main compounds responsible for differences in the aroma of LYT subjected to different roasting methods. Aroma recombination and addition experiments verified these findings. All in all, charcoal roasting enhances the rice crust and burnt aromas of LYT, and drum roasting facilitates the presentation of floral and corn aromas. This study provides a theoretical basis for the processing of high-quality LYT.

Large-leaf yellow tea (LYT) is processed from both leaves and stems, resulting in a distinctive rice crust-like aroma. Tea stems may contribute differently to the aroma of LYT than leaves. This study aimed to clarify the specific contribution of stems to LYT. The volatile compounds in different components of LYT were extracted and analyzed using a combination of headspace solid-phase microextraction and stir bar sorptive extraction coupled with gas chromatography-olfactory-mass spectrometry. The results revealed high concentrations of compounds with roasty attributes in stems such as 2-ethyl-3,5-dimethylpyrazine (OAV 153-208) and 2-ethyl-3,6-dimethylpyrazine (OAV 111-140). Aroma recombination and addition experiments confirmed that the roasty aroma provided by stems plays a pivotal role in the formation of the distinctive flavor of LYT. This study offers novel insights into the contribution of stems to the aroma of LYT, which can be used for processing and quality enhancement of roasted tea.

Grain Rain Period (GRP), one of the 24 solar terms in China, signifies a crucial phase for the transformation of tea quality, especially for Lu'an Guapian (LAGP) tea. During GRP, LAGP teas showed 3 distinct aroma profiles, each spanning 3-4 days. Specifically, the sensory evaluation result revealed that LAGP tea exhibited stronger flowery and fresh aromas in the early phase, with the soybean-like aroma significantly intensifying as the harvest period progressed during GRP. Furthermore, the key contributors to the aroma profile and its variation during GRP were identified as indole, δ-decalactone, geraniol, linalool, decanal, jasmone, (E)-β-ionone, benzeneacetaldehyde, dihydroactinolide, nonanal, octanal, (E)-isoeugenol, (E,E)-2,4-nonadienal, 4-ketoisophorone, (E,Z)-2,6-nonadienal, and 1-octen-3-one. Additionally, we proposed a binary blending strategy using sensory evaluation with the methods of triangle test and normal distribution fitting to predict the blending threshold accurately. This study elucidated the dynamics of LAGP tea aroma during GRP and offered insights for tea blending optimization.

Colorant adulteration is a common problem in tea safety control; thus, a rapid identification method is required. In this study, we optimized the fabrication parameters of various sensors to enhance their performance. R6G was used as a probe molecule, demonstrating that the sensnor remained stable for 120 days. Based on surface-enhanced Raman spectroscopy, the optimized sensors were used to identify and quantify mixed colorants (sunset yellow, lemon yellow, carmine, and erythrosine). Partial least squares prediction models were developed for each colorant (0.5-300 μg/mL), with R2 > 0.900 and RPD > 2.27; these indicated the accuracy of the sensors. The results also revealed a model recovery range of 95.9 % to 116 %, with RSD < 3.94 %, indicating the universality of our proposed method. Overall, the proposed method enables the detection of mixed-colorant adulteration in black tea within 3 min, thereby representing a novel method for the assessment of tea quality.

Lu’an Guapian (LAGP) tea is one of the most famous teas in China. However, research on its suitable processing varieties is still lacking. This study analyzed the quality of LAGP tea made from three different tea varieties, namely, ‘Anhui1’ (AH1), ‘Quntizhong’ (QTZ), and ‘Shuchazao’ (SCZ), using molecular sensory science and metabolomics techniques. The results showed that AH1 had a strong floral aroma and the strongest umami flavor, while QTZ had a distinct roasted aroma and a mellow taste. SCZ had a cooked corn-like aroma and the highest bitterness and astringency owing to the high tea polyphenol contents and low free amino acid contents. The study also identified 12 key aroma-active compounds, with trans-beta-ionone and 2-ethyl-3,5-dimethyl-pyrazine contributing the most to floral and roasted aromas, respectively. The results of this study provide a theoretical and practical basis for selecting and breeding high-quality varieties of LAGP tea and stabilizing its quality.

During their co-evolution with herbivorous insects, plants have developed multiple defense strategies that resist pests, such as releasing a blend of herbivory-induced plant volatiles (HIPVs) that repel pests or recruit their natural enemies. However, the responses of insects to HIPVs in maize (Zea mays L.) are not well understood. Here, we demonstrate that the Asian corn borer (ACB, Ostrinia furnacalis), a major insect pest of maize, shows a preference for maize pre-infested with ACB larvae rather than being repelled by these plants. Through combined transcriptomic and metabolomics analysis of ACB-infested maize seedlings, we identified two substances that explain this behavior: (E)-4,8-dimethylnona-1,3,7-triene (DMNT) and (3E,7E)-4,8,12-trimethyltrideca-1,3,7,11-tetraene (TMTT). DMNT and TMTT attracted ACB larvae, and knocking out the maize genes responsible for their biosynthesis via gene editing impaired this attraction. External supplementation with DMNT/TMTT hampered the larvae's ability to locate pre-infested maize. These findings uncover a novel role for DMNT and TMTT in driving the behavior of ACB. Genetic modification of maize to make it less detectable by ACB might be an effective strategy for developing maize germplasm resistant to ACB and for managing this pest effectively in the field.

An optimized yellowing process for yellow tea (YT) was recently developed. The study found that the optimized yellowing process caused a significant increase in sweet and floral aromas by 31.3% and 24.0%, respectively. A total of 21 aroma-active compounds were identified using gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactometry (GC-O) combined with sensomics analysis. Quantification of the 15 aroma active compounds and calculation of odor activity values (OAVs) showed that the OAVs of sweet and floral aroma compounds increased significantly by 986.2% and 46.4%, respectively, after the optimized yellowing process. Sensory-directed aroma reconstitution and omission experiments confirmed that dimethyl sulfide, 3methylbutanal, fl-ionone, fl-damascenone, geraniol, phenylacetaldehyde, and linalool were the key odorants in YT after the optimized yellowing process. Odorant addition tests further demonstrated that fl-damascenone (OAV 590.4) was the main odorant for YT sweet aroma enhancement, while fl-ionone (OAV 884.6) was the main odorant for YT floral aroma enhancement.

Sunlight withering (SWT) enhanced the floral aroma of white tea, whereas withering–tank withering (WWT) enriched its grassy aroma. This study investigated the impact of diverse withering methods on white tea aroma, examining aroma formation mechanisms by analyzing changes in essential compounds, their precursors, and enzyme activities during these treatments. Findings revealed that tea at 50% moisture concentration decreased the concentration of isopentenyl pyrophosphate and dimethylallyl pyrophosphate, leading to increased levels of linalool, geraniol, and β-myrcene. Sunlight spurred non-enzymatic reactions, elevating β-ionone concentration. The breakdown of linoleic and linolenic acids increased the hexanal and (Z)-3-hexenol levels. Enzyme activity analysis indicated that the prominent floral aroma in SWT was linked to heightened geranyl pyrophosphate synthase and alcohol dehydrogenase activity, enriching terpene–catalyzed products and benzeneacetaldehyde concentration, respectively. Elevated levels of lipoxygenase and arogenate dehydratase promoted grassy compounds in WWT. This study underscores how withering methods shape white tea aromas and offers operational insights.

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 pro-cessed 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)-beta-ionone, isoamyl acetate, and 2-methylpropanal enriched in HX and contributed to the floral-like aroma, while 3-methylbutanal, 2-ethyl-1-hexanol, indole, beta-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.