Green Odor Research Articles

Olfactory stimulation with multiple odorants prevents stress-induced cognitive and psychological alterations

Abstract Acute and chronic stress markedly affects behavior by triggering sympathetic nervous system activation and several hypothalamus-pituitary-adrenal-dependent responses. Brain regions of the limbic system are responsible for the regulation of stress response, and different reports have demonstrated that their activity can be influenced by olfactory stimuli. Here we report that, in mice exposed to acute restraint stress, olfactory stimulation employing a combination of three odorants, i.e., vanillin, limonene and green odor (trans-2-hexenal and cis-3-hexenol) decreased anxiety behavior, assessed in the elevated plus maze, and halted recognition and spatial memory deficits, as appraised in two different object recognition tasks. Of note, when applied singularly, the same odorants were unable to block the detrimental effects of stress. We also found that the multiple odorants stimulation prevented the development of depressive symptoms assessed by the sucrose splash test and forced swim test in an experimental model of depression, i.e., mice exposed to a chronic unpredictable stress paradigm, and reduced interleukin 1β levels in the prefrontal cortex of depressed mice. Collectively, our data indicate that olfactory stimulation counteracts the detrimental effects of acute and chronic stress on mood regulation and cognitive functions, thus representing a potential tool for the treatment of stress-induced disorders.

Biochemical characterization of CsCXEs: Carboxylesterase enhances the biosynthesis of green odor volatiles during tea processing

Biochemical characterization of CsCXEs: Carboxylesterase enhances the biosynthesis of green odor volatiles during tea processing

Comprehensive Characterization of Tuber maculatum, New in Uruguay: Morphological, Molecular, and Aromatic Analyses.

Although only a few species of Tuber account for the major truffle sales volume, many species that are not considered delicacies are finding their way to the market, especially in regions where the traditionally appreciated ones do not occur. This is the case for whitish truffles. Specimens of whitish truffles were collected in pecan (Carya illinoinensis) orchards in Uruguay in October 2021. Morphological and molecular methods were used to characterize and assess their identity as Tuber maculatum Vittad. An SPME extraction of volatile compounds and GC-MS analyses were performed to characterize the aromatic profile of these specimens and evaluate their potential applications. Among the 60 VOCs detected, 3-octenone (mushroom odor), 3-octanol (moss, nut, mushroom odor), and 2H-pyran-2-one (no odor), followed by octen-1-ol-acetate (no odor) and 2-undecanone (orange, fresh, green odor) were the major compounds in T. maculatum fruiting bodies. The attributes of exotic edible mushrooms of commercial value in the region are highlighted. In particular, this work emphasizes the characteristics of truffles as a byproduct of pecan cultivation.

Effects of Pelletized and Coated Organic Fertilizers on Flavor Compounds of Tomato Fruits and Leaves.

The application of organic fertilizers is one of the most important agricultural measures aimed at improving the flavor and productivity of Lycopersicon esculentum, with the granulation and coating of organic fertilizers, which can reduce seepage losses of great significance to the ecosystem. In this study, Jingcai 8 tomato was selected as the test material. Headspace solid-phase microextraction and gas chromatography-mass spectrometry (HS-SPME-GC-MS) methods were used to investigate the effects of different pelletized organic fertilizers and various coating materials on the flavor profile of the tomatoes. The results indicated that 67 volatile organic compounds (VOCs) were identified in the tomato fruits and 62 volatile compounds were identified in the leaves under different fertilizer treatments. The volatile compound content of the fruits in the BP treatment group was 35.38 μg/g, which was higher than that in other treatment groups, and the volatile compound content of the leaves was lower. A differential compound analysis with log2|fold change| ≥ 1 and variable important in projection (VIP) > 1 highlighted styrene, 3-methyl-1-butanol, and (E, E)-2,4-hexadienal as the major up-regulated compounds and methyl salicylate as the major down-regulated compound in the tomato fruit BCK (control) vs. BP. Moreover, the α-phellandrene content decreased in the tomato leaves. In addition, an analysis of the tomato fruit differential compounds and compounds with odor activity values (OAV) of ≥ 1, considering the OAV values of characteristic aroma compounds, identified key compounds affecting the flavor of the tomato fruits under the BP treatment. These included 2-nonenal, (E)-2-pentylfuran, trans-β-ionone, 1-penten-3-one, (E, E)-2,4-hexadienal, and 3-hexenol (fruity, floral, and herbaceous odors), (E, E)-2,4-heptadienal (fatty odor), and hexanal (green odor). The combined results analysis of the volatile compound content, differential compounds, and OAV values of characteristic aroma compounds aimed to clarify that the BP treatment group, which applied pelletized, large-grain organic fertilizer with polyurethane (pozzolanic + small-grain oil-coated + 2% paraffinic + 4% polyurethane) as a coating material, proved to be most effective in influencing the flavor of the tomato fruits. This finding lays the foundation for its potential commercial application in artificial orchards.

Analysis of Volatile Aroma Components in Different Parts of Shiitake Mushroom (Lentinus edodes) Treated with Ultraviolet C Light-Emitting Diodes Based on Gas Chromatography-Ion Mobility Spectroscopy.

Further assessment of ultraviolet C light-emitting diode (UVC-LED) irradiation for influencing shiitake mushrooms' (Lentinus edodes) volatile and sensory properties is needed. In this study, a comparison of UVC-LED irradiation treatment on the flavor profiles in various parts of shiitake mushrooms was conducted using gas chromatography-ion mobility spectrometry (GC-IMS) and sensory analysis. Sixty-three volatile compounds were identified in shiitake mushrooms. The fresh shiitake mushrooms were characterized by the highest values of raw mushroom odors. After UVC-LED treatment, the content of C8 alcohols decreased, especially that of 1-octen-3-ol, while the content of aldehydes increased, especially the content of nonanal and decanal. The score of fatty and green odors was enhanced. For fresh samples, the mushroom odors decreased and the mushroom-like odors weakened more sharply when treated in ethanol suspension than when treated with direct irradiation. The fruit odors were enhanced using direct UVC-LED irradiation for fresh mushroom samples and the onion flavor decreased. As for shiitake mushroom powder in ethanol suspension treated with UVC-LED, the sweaty and almond odor scores decreased and the vitamin D2 content in mushroom caps and stems reached 668.79 μg/g (dw) and 399.45 μg/g (dw), respectively. The results obtained from this study demonstrate that UVC-LED treatment produced rich-flavored, quality mushroom products.

Mlp4green: A Binary Classification Approach Specifically for Green Odor.

Fresh green leaves give off a smell known as "green odor." It has antibacterial qualities and can be used to attract or repel insects. However, a common method for evaluating green odor molecules has never existed. Machine learning techniques are widely used in research to forecast molecular attributes for binary classification. In this work, the green odor molecules were first trained and learned using machine learning methods, and then clustering analysis and molecular docking were performed to further explore their molecular characteristics and mechanisms of action. For comparison, four algorithmic models were employed, MLP performed the best in all metrics, including Accuracy, Precision, Average Precision, Matthews coefficient, and Area under curve. We determined by difference analysis that, in comparison to non-green odor molecules, green odor molecules have a lower molecular mass and fewer electrons. Based on the MLP algorithm, we constructed a binary classification prediction website for green odors. The first application of deep learning techniques to the study of green odor molecules can be seen as a signal of a new era in which green odor research has advanced into intelligence and standardization.

Sniffing Out the Sustainable Future: The Renewability Revolution in Fragrance Chemistry.

In this review, the impact of the transition from today's resource-wasting petrochemical economy towards a 100/100 renewable and biodegradable future is discussed with respect to the fragrance families: "citrus", "green", "fruity", "floral", "floriental", "oriental", "woody", "chypre" and "fougère". After benchmark data on ingredients usage, definitions on biodegradation and sustainability are given. Celebrating the 150th anniversary of synthetic vanillin, its historic synthesis from renewable starting materials serves as introduction. In the grand scheme of things, citrus scents upcycled from the beverages industry, are already an ideal case for 100/100 with new opportunities for artificial essential oils. In the fruity domain, transparent and lactonic ingredients are available in a sustainable manner. However, in the domain of green odorants, there is a lack of green chemistry for important key materials. In the floral family, renewability is more critical than biodegradability, but cost is an issue. Thanks to Ambrox and maltol, florientals and orientals will persist, while woody notes severely lack an Iso E Super replacer. In the chypre genre, patchouli became the new moss, but more musks are increasingly in demand. With their high percentage of linalool and dihydromyrcenol, the construction of fougères could well become a precedent for other families, despite challenges in vetiver and salicylates. Still, the challenges exemplified here create immense opportunities for new perfumery materials.

The effects of different rootstocks on aroma components, activities and genes expression of aroma-related enzymes in oriental melon fruit.

Grafting is widely applied in the cultivation of melon. In this study, 'Qinmi No.1' (Cucumis melo L.(QG)) and 'Ribenxuesong' (Cucurbita maxima Duch. (RG)) were used as rootstocks for 'Qingxin Yangjiaocui' (Cucumis melo L.). The results showed that grafting with muskmelon rootstocks had no significant effect on fruit aroma, but grafting with pumpkin rootstocks significantly reduced the odor intensity and odor preference scores of melon fruits. Compared with the fruits from self-grafted plants (SG), four new aromatic volatiles with a sweet smell were detected, the alcohol dehydrogenase (ADH) activity was significantly decreased at 30 DAP, but unaffected at 42 DAP in QG fruits. There was no difference for alcohol acetyltransferase (AAT) activity between QG and SG fruits. The expression level of CmADH2 was significantly higher at 30 DAP and 42 DAP, but CmAAT2 was significantly lower at 42 DAP in QG fruits compared with SG fruits. In RG fruits, the main aroma compounds including butanoic acid ethyl ester, 2-methyl-2-butene-1-al, and 2-methylheptan-1-al were absent, while the volatile compounds with unpleasant odor characteristics including trans, cis-2,6-nonadien-1-ol, (E,E)-2,4-heptadienal, octanoic acid, and styrene were detected. Compared with SG fruits, 1-nonanol and 1-heptanol with green odor characteristics were significantly increased, but eucalyptol and farnesene with fruity aroma characteristics were significantly decreased in RG fruits. The ADH activity of RG fruits was significantly lower than that of SG fruits at 30 DAP and the AAT activity was significantly lower than that of SG fruits at 42 DAP. In addition, the expression levels of CmADH and CmAAT homologs in RG fruits were significantly lower than those in SG or QG fruits. These results show that grafting with pumpkin rootstocks affected the main aroma components, reduced ADH and AAT activities, and down-regulated the expression levels of CmADHs and CmAATs in the melon fruits. This study reveals the mechanism of different rootstocks on melon fruit aroma quality, and lays a theoretical foundation for the selection of rootstocks in melon production. Future studies using overexpression or CRISPR/CAS system to obtain stable transgenic lines of genes encoding key aromatic volatiles, would be promising to effectively improve the flavor quality of melon.

Effects of defatting and cooking methods on pig large intestines volatile compounds by flavor omics and fatty acids

Pig large intestines (PLIs) are a food with a selective preference globally because of characteristic odors. To investigate the effect of defatting and different cooking methods on the volatile compounds of PLIs, defatted and nondefatted samples were cooked using steaming, water boiling, and frying. A total of 63 volatiles were identified, including 22 compounds detected in all samples. Using odor activity value (OAV) and sensory evaluation, 3-methyl indole and p-cresol, with animal and fecal odors, respectively, were identified as the key off-odors of PLIs. The three cooking methods increased the concentration of aldehydes and endowed samples with fatty and green odors derived from lipid oxidation, especially C18:1n9c and C18:2n6c. Frying significantly increased the content of (E)-2-heptenal and (E,E)-2,4-decadienal (P < 0.05) due to higher contents of C18:2n6c. Compared with steaming and frying, water boiling could significantly reduce the occurrence of off-odors and had the best result combined with defatting. Using orthogonal partial least squares-discriminant analysis (OPLS-DA) and variable importance for the projection (VIP), p-cresol could act as a marker to discriminate samples with different treatments.

Characterizing and Decoding the Effects of Different Fermentation Levels on Key Aroma Substances of Congou Black Tea by Sensomics.

Fermentation is the key technology for black tea aroma formation. The key aroma substances of black tea at different fermentation stages (unfermented (WDY), underfermented (F1H), fully fermented (F4H), and overfermented (F8H)) were characterized by the methodology of Sensomics. Aroma extract dilution analysis was performed on volatile fractions extracted by using solvent-assisted flavor evaporation and solid-phase microextraction, yielding 93 odor-active areas. Internal standard method plus stable isotope dilution analysis was used for quantitative analysis. The omission experiment identified 23 aroma substances. Further reduction and addition experiments revealed phenylacetaldehyde, (E,E)-2,4-heptadienal, geraniol, linalool, β-damascenone, 2-methylbutyraldehyde, dimethyl sulfide, and isovaleraldehyde with odor activity values (OAV) > 100 as the characteristic aroma components of F4H and also as the main contributors to aroma differences between different fermentation degrees. The green odor of (E,E)-2,4-heptadienal was highlighted in WDY and F1H relative to that in F4H due to the lower contribution of phenylacetaldehyde and β-damascenone in the former two samples. Additionally, excessive OAV increase of fatty aldehydes in F8H masked its similar floral and fruity aroma.

The Impact of Different Cooking Methods on the Flavor Profile of Fermented Chinese Spicy Cabbage.

Chinese spicy cabbage (CSC) is a common traditional fermented vegetable mainly made of Chinese cabbage. In addition to eating raw, boiling and stir-frying are the most common cooking methods for CSC. To identify the impacts of boiling or stir-frying on the quality of CSC, the physicochemical properties, flavor compounds, and sensory properties of CSC were analyzed. A total of 47 volatile flavor compounds (VFCs) were detected by gas chromatography-mass spectrometry. Sulfide was determined as the main flavor compound of CSC, mainly contributed by cabbage, garlic, and onion odors. The content of sulfide decreased significantly after cooking. Nonanal, geranyl acetate, and linalool were newly generated after boiling with odor activity value (OAV) > 1, and contributed fatty, sweet, fruity, and floral odors to BL-CSC. 1-Octen-3-one, 1-octen-3-ol, octanal, nonanal, and (E)-2-nonenal were newly generated after stir-frying with OAV > 1, and contributed mushroom, fatty, and green odors to SF-CSC. Diallyl trisulfide, nonanal, (E)-β-ionone, β-sesquiphellandrene, and (E)-2-decenal were considered as the potential key aroma compounds (KACs) to distinguish the CSCs after different heat treatment. After cooking, the total titratable acidity of CSC increased and the sensory properties changed significantly. This study provides valuable information and guidance on the sensory and flavor changes of thermal processing fermented vegetables.

Pulsed electric field processing of green tea-infused chardonnay wine: Effects on physicochemical properties, antioxidant activities, phenolic and volatile compounds

Pulsed electric field (PEF) was used to develop a novel Chardonnay wine infused with green tea, where the physicochemical characteristics (pH, titratable acidity, color) were modulated. The PEF processing conditions were optimized via response surface methodology by evaluating antioxidant activity (assessed by DPPH, FRAP and ABTS assays), total free phenolic content (TPC), total free flavonoid content (TFC), and volatile content. The optimum conditions were determined as electric field strength 1.3 kV/cm and pulse number 10. The PEF-processed green tea-infused wines were also analyzed for the phenolic and volatile profiles. A total of 178 phenolics and non-phenolics were identified by HPLC-DAD-ESI-QTOF-MS/MS in the PEF-treated wines. The application of PEF resulted in additional 20 phenolic compounds and 14 non-phenolic compounds absent in either Chardonnay or green tea. Catechin was the most abundant phenolic compound, while the enhanced antioxidant power was mainly driven by epigallocatechin. There were 49 volatiles detected by HS-SPME-GC-MS in the PEF-treated wines, with 15 volatiles as odor-active compounds. Under both artificial saliva spiked and non-spiked conditions, green tea infusion diminished fruity, floral and spicy odors, and intensified citrus and green odors. The PEF treatment (0.1 and 0.5 kV/cm) could impart more intense citrus and green aromas from tea to wine. Saliva addition decreased the release of volatile acids, alcohols, esters and aldehydes, and increased the release of benzenoids and terpenes. This study forecasted a promising future of PEF as a time and energy efficient technique in the production of flavored wine with enhanced functionalities and desired aromas.

Characterization of odor-active compounds of various pea preparations by GC-MS, GC-O, and their correlation with sensory attributes

Pea preparations (flours, concentrates, and isolates) are increasingly used in plant-based products, but their characteristic odor is often causing problems. Advanced knowledge of the aroma profile of pea preparations could improve understanding of how pea-based ingredients affect sensory properties of foods.This study investigated the aroma profiles of different pea preparations using solid-phase microextraction (HS-SPME) followed by gas chromatography-mass spectrometry (GC-MS), gas chromatography-olfactometry (GC-O), and descriptive sensory analysis. The GC-MS analysis included MRM detection of methoxypyrazines, which significantly contribute to the flavor of pea preparations.More than 100 volatile compounds were identified in pea preparation samples by GC-MS, aldehydes being the main molecules, and 39 aroma-active compounds were registered by GC-O assessors. Sensory attributes of pea protein preparations were compared with analytical data to find the characteristic aroma-active compounds. Sensory panel evaluation showed noticeable differences between the pea preparations. Unsaturated aldehydes, which impart green odor, and methoxypyrazines, with pea-like and beany notes, enhance the sensory perception of green and pea-like characteristics in pea preparations. Methanethiol increased sulfur-like odor in pea protein isolate A. β-Damascenone had high modified frequency in pea protein isolate C, enhancing honey-like attributes. Methanethiol and β-damascenone were not reported previously as odor-active compounds in pea protein preparations.

Membrane filtration without adding lime water combined with vacuum heating enhances green odor in brown sugar processing

Compared with the clarification method of adding Ca(OH)2 and the traditional heating method, membrane filtration without adding Ca(OH)2 and vacuum heating affect the aroma of brown sugar processing by reducing cations, pH and heating temperature. HS-SPME-GC-MS were used to extract and analyze volatiles formed in the production process of brown sugar (obtained by different clarification methods and heating methods), and aroma attributes were analyzed via quantitative descriptive analysis. The results showed that the green and fruity notes were higher in the brown sugar obtained by vacuum heating, especially for the samples without adding Ca(OH)2; the roasted and caramel notes were enhanced by high-temperature. Meanwhile, the aroma attributes had the same tendency as the odorants. Sugarcane juice and syrup had similar volatiles compared to brown sugar. These data indicate that membrane filtration without adding Ca(OH)2 and vacuum heating provided more fruity and green notes to brown sugar and enriched the brown sugar aroma.

The impact of thermal extraction on the quality of Phyllanthus emblica Linn. fruit: A systematic study based on compositional changes

Phyllanthus emblica (PE) is a well-known tropical crop with a distinct flavor and several health advantages. From the standpoint of the transformation of volatile and nonvolatile components, the purpose of this paper is to investigate the impact of heat extraction on the flavor attributes and biological activity of PE. According to studies, thermal extraction can greatly enhance the amount of the molecule 4,5-epoxy-(E)-2-decanal with a green odor while removing offensive scents like 2-isobutyl-3-methoxy pyrazine. Temporal dominant description evaluation found that with the extension of thermal extraction time, the five flavors of PE are enhanced. According to high-resolution mass spectrometry studies, the primary reaction processes during thermal extraction were the hydrolysis and condensation of tannin and flavonoid glycosidic bonds. The main core groups of compound transformation were galloyl and hexahydroxydibenzoyl (HHDP), which led to the final product gallic acid and ellagic acid were significantly increased. Finally, it was found that thermal extraction can significantly enhance the antioxidant and antibacterial activities of PE.

Variations in physicochemical characteristics, antioxidant activity, phenolic and volatile profiles, and sensory attributes of tea-flavored Chardonnay wine during bottle aging.

A novel Chardonnay wine flavored with either green tea or black tea was subjected to bottle aging for 9 months, and the physicochemical properties, antioxidant capacity, total phenolic content, volatile content and sensory properties were monitored. There were 272 phenolic and non-phenolic compounds characterized in the aged Chardonnay wines, including newly formed 9, 1, 3 and 8 phenolic compounds and 10, 6, 1 and 6 non-phenolic compounds after aging for 1, 3, 6 and 9 months, respectively. For all the aged wines, catechin was determined as the most abundant phenolic compound, and epigallocatechin mainly contributed toward the antioxidant power. A total of 54 volatile compounds were identified in the aged Chardonnay wines, including 17 odor-active compounds. The aging process diminished floral and fruity odors, but intensified green odor. The consumer study revealed the highest consumer liking for 1% (w/v) black tea infused wine. This study revealed the quality and bioactivity of this novel flavored wine type during aging which is critical to understand the shelf-life and functionality of the product.

Characterization of different meat flavor compounds in Guangdong small-ear spotted and Yorkshire pork using two-dimensional gas chromatography–time-of-flight mass spectrometry and multi-omics

In China, indigenous pigs are popular due to their excellent meat quality and unique flavor. In this study, the unique flavor was investigated using Guangdong small-ear spotted pig (GD) and their hybrid progeny, which produced high-end pork in the Chinese market. Two-dimensional gas chromatography-time-of-flight mass spectrometry (GC × GC-TOF MS) was used to analyze and quantify volatile organic compounds (VOCs) in the two pork types for identifying the unique flavor of these very popular pigs. The flavor is imparted by alkanes, aldehydes, ketones, and ethers. Flavor imparting compounds mainly include methyl isobutyl ketone, octane, pentane, and 3-ethyl-2, 2-dimethylheptane. High levels of volatilization of such compounds generated ethereal, acetonic, sweet, and green odors in the pork of GD. Hybrid offspring of Chinese and Western pig breeds can also inherit such special aromas, which are sometimes even more intense, with increased meat yield. Multi-omics analysis of the transcriptome and metabolome showed that AMD1 (Adenosylmethionine Decarboxylase 1) affects the p-cresol content by regulating the polyamine pathway, affecting the unique flavor of GD. This study revealed the unique flavor composition of GD, analyzed the advantages of species hybridization, and thus, provides a new direction and theoretical basis for pork quality improvement.

Digital Evaluation of Aroma Intensity and Odor Characteristics of Tea with Different Types-Based on OAV-Splitting Method.

Aroma is one of the most important quality indicators of tea. However, this evaluation method is a subjective one. In this study, the volatiles of tea with 5 types were determined by headspace solid-phase micro-extraction (HS-SPME) combined with gas chromatography mass spectrometry (GC-MS). The aroma intensity and odor characteristics of teas were comparatively analyzed based on the OAV-splitting method. The results showed that OAV were green tea (492.02), red tea (471.88), oolong tea (302.74), white tea (68.10), and dark tea (55.98). The odor index I(o) indicated that green tea was strong-flavor tea with highlight green accompanied by fruity, woody and fatty odors; oolong tea was strong-flavor tea with fruity and fatty accompanied by woody, floral and green odors; red tea was strong-flavor tea with highlight fruity accompanied by woody, green and floral odors; white tea was a light-flavor tea with floral, woody and green odors; and dark tea was light-flavor tea with woody and floral notes accompanied by fatty and green odors. These results fitted perfectly with the people’s consensus on these teas, and proved that the OAV-splitting method is feasible to evaluate the aroma intensity and odor characteristics of tea aroma. We suggest that the digital evaluation of tea aroma can facilitate people’s communication.

Potent odorants and sensory characteristics of the soft white cheese “Jben”: Effect of salt content

AbstractJben is a highly popular soft white cheese consumed in Morocco for its nutritional and health benefits. The aroma and aroma‐active compounds of salted and unsalted Jben were investigated in this study. Aroma compounds were isolated by the purge and trap extraction (PTE) method and analysed by aroma extract dilution analysis (AEDA) and gas chromatography–mass spectrometry‐olfactometry (GC–MS‐O). A total of 36 aroma compounds were characterized Jben samples, among them 30 and 32 compounds were detected in the salted Jben (260.88 mg/kg) and unsalted Jben (230.04 mg/kg) samples respectively. The alcohols, followed by acids and esters, were the most dominant aroma compounds in both samples. A total of 22 (salted Jben) and 25 (unsalted Jben) aroma‐active compounds were detected in the samples using GC–MS‐O. Based on the flavour dilution (FD) factor, the most potent aroma‐active compounds were ethyl caproate (FD = 2048, OAV = 2306, overripe fruit and pineapple odours), isoamyl acetate (FD = 2048, OAV = 2491, apple odour), hexyl acetate (FD = 1024, OAV = 1355, green odour), and isoamyl butyrate (FD = 1024, OAV = 932, green‐fruity odour) for the salted Jben sample and ethyl caproate (FD = 2048, OAV = 2388) and isoamyl acetate (FD = 1024, OAV = 880) for the unsalted Jben sample. The odour activity values (OAVs) ranged from 1 to 2491. The lowest OAVs represent the low aromatic active compounds (FD ≤ 32). The GC–MS‐O results were also consistent with the results of sensory analysis of the Jben samples.

Characterization of a new (Z)-3:(E)-2-hexenal isomerase from tea (Camellia sinensis) involved in the conversion of (Z)-3-hexenal to (E)-2-hexenal

Two major green leaf volatiles (GLVs) in tea that contribute greatly to tea aroma, particularly the green odor, are (E)-2-hexenal and (Z)-3-hexenal. Until now, their formation and related mechanisms during tea manufacture have remained unclear. Our data showed that the contents of (E)-2-hexenal and (Z)-3-hexenal increased more than 1000-fold after live tea leaves were torn. Subsequently, a new (Z)-3:(E)-2-hexenal isomerase (CsHI) was identified in Camellia sinensis. CsHI irreversibly catalyzed the conversion of (Z)-3-hexenal to (E)-2-hexenal. Abiotic stresses including low temperature, dehydration, and mechanical wounding, did not influence the (E)-2-hexenal content in intact tea leaves during withering, but regulated the proportions of (Z)-3-hexenal and (E)-2-hexenal in torn leaves by modulating CsHI at the transcript level. For the first time, this work reveals the formation of (E)-2-hexenal during tea processing and suggests that CsHI may play a pivotal role in tea flavor development as well as in plant defense against abiotic stresses.