Volatile Organic Compounds (VOCs) and Their Role in Tea Aroma and Flavor

Volatile organic compounds (VOCs) are pivotal in shaping the aroma and flavor profile of tea, serving as the key contributors to its sensory appeal. These compounds distinguish different tea types—green, black, oolong, and white tea—through their unique combinations and concentrations. VOCs are generated during tea leaf processing, which involves steps such as withering, rolling, oxidation, and drying. The diversity of VOCs is influenced by the tea variety, cultivation environment, and the meticulous methods used during production.

Key VOCs in Tea and Their Contributions

Several classes of VOCs dominate the aroma and flavor landscape of tea. Terpenes, such as linalool and geraniol, are responsible for floral and fruity notes, while aldehydes like hexanal and benzaldehyde contribute fresh green and almond-like scents. Alcohols, including phenylethyl alcohol, enhance sweet and floral characteristics. Esters, such as methyl salicylate, lend minty and wintergreen flavors, and ketones like β-ionone add depth and complexity. These VOCs interact synergistically, creating the intricate flavor profiles that tea enthusiasts cherish.

Factors Influencing VOC Composition

The composition and concentration of VOCs in tea are shaped by multiple factors. The cultivar and growing conditions, such as altitude, soil composition, and climate, play a fundamental role. For instance, high-altitude teas often exhibit enhanced floral and sweet notes due to cooler temperatures that slow plant metabolism and promote VOC accumulation.

Processing methods are equally critical. In black tea, extensive oxidation converts catechins into theaflavins and thearubigins, forming complex VOCs that yield a robust and malty flavor. Conversely, minimal oxidation in green tea preserves lighter, grassy notes and simpler VOC profiles. Oolong tea, with partial oxidation, strikes a balance, featuring a spectrum of fruity, floral, and woody aromas.

Innovations and Trends

Advancements in analytical techniques, such as gas chromatography-mass spectrometry (GC-MS), have enabled precise identification of VOCs, allowing producers to refine processing methods for specific flavor outcomes. Additionally, sustainable practices, like organic cultivation, have shown potential to influence VOC composition positively by improving plant health and soil biodiversity.

Conclusion

VOCs are essential to the distinctive sensory experiences that tea offers. By understanding the intricate interplay of these compounds, tea producers can craft superior flavors, while enthusiasts can deepen their appreciation for tea’s rich diversity. As research and innovation progress, the nuanced art of tea cultivation and processing continues to evolve, enhancing both its tradition and appeal.
Volatile Organic Compounds (VOCs) and Their Role in Tea Aroma and Flavor

Flavor and aroma of black tea: Complex mixture of essential oil

Flavor is the most important factor for quality of tea. The tea aroma is one of the most important factors that define tea quality, and it has a great influence on its appreciation by consumers.

Extensive research on the volatile components from tea or fresh tea leaf was carried out by many authors and a large number of components (70-80) were identified.

Aroma of tea is complex mixture of volatiles consisting of alcohols, terpenes, sesquiterpenes, nitrogenous aromatic compounds and oxygenated hydrocarbons present in trace amounts.

The yield of crude essential oils: fresh leaf, 6.8 mg96 of fresh leaf, 30.9 mg% dry basis; black tea, 7.8 mg% of black tea, 8.2 mg96 dry basis.

Both of them had the characteristic odor each other and reminded of their original materials; the volatiles from fresh leaf were greenish, unripe and stimulant odor, however, those from black tea had a sweet aroma.

The essential oil extracted from tea has a very wide range of applications in the fields of food, cosmetics, flavors and fragrances, and the cigarette industry. The extraction of essential oil from abandoned tea can reduce the amount of wasted tea and can bring stupendous economic benefits to tea farmers and the essential oil industry.
Flavor and aroma of black tea: Complex mixture of essential oil

Flavour and aroma of tea

The oxidation products such as theaflvins and therubigins contribute to tea colour and taste of the black tea. Moreover, tea quality is also determined by the processing techniques employed.

The flavour of tea is principally determined by the chemical components it contains. Volatile compounds contribute to the aroma and non-volatile compounds to the taste.

The principal components which determine the aroma, flavour and physiological action of tea are:
*An essential oil: about 0.5%, this is probably formed during fermentation.
*Caffeine: 1.8 to 5.9%. Caffeine (1, 3, 7-trimethylxanthine) is one of the major alkaloids in tea.
*Flavonoids, which were previously called tea tannins or tea polyphenols, are the main phenolic compounds comprising 20–40% of dry matter in young shoots of tea plants. The characteristics of made tea, including colour, taste, and aroma, are directly or indirectly associated with these phenolic compounds.

Some 140 components have been reported as contributing to the aroma and flavour of tea.

Chlorophyll, carotenoids, lipids and volatile compounds are not major constituents in a tea brew but they also play an important role in the development of the aroma.

The flavour of made tea is largely affected by the abundance of chemical constituents and their relative composition in young shoots.

Caffeine together with black tea polyphenols was necessary for the expression of reasonable amounts of tangy astringency. Decaffeination may change the nature of astringency from tangy to non-tangy type.

The chemical composition of tea depends on the following factors: genetic strain, climatic conditions, soil, growth altitude and horticultural practices, the plucking season, sorting (grading) of the leaves, the processing, storage, etc.

The aim of making good tea is to obtain the maximum extraction of caffeine. Most commercially available teas are blends, designed to satisfy the tastes of the customer.
Flavour and aroma of tea

Lapsang souchong tea

Lapsang souchong (Zhengshan Xiaozhong) is a special black tea produced in the Wuyi (Bohea) Mountain area in southeastern. The Wuyi Mountains are located in northwestern Fujian Province, and contain the Huanggangshan, the highest peak in southeastern China, at an elevation of 2158m.

The tea is an ancient Chinese black tea, created by drying large tea leaves over smoky pine fires, resulting in a truly distinctive flavor.

Lapsang souchong from the original source is increasingly expensive because of increasing demand for this variety of tea, as Wuyi is a small area.

The tea is twisted leaf made from a few steps down from the bud. This rare long leaf gains its distinctive “tarry” flavor and smoky tang from the pine fires. Rich in taste and smoky aroma, it produces a deep red liquor when brewed. China Lapsang Souchong has a smokier taste and aroma than Hu-Kwa Formosan Lapsang Souchong tea.
Lapsang souchong tea

Volatile compound responsible for aroma of tea

The flavor of tea can be divided into two categories: aroma, which consists mainly of volatile compounds; and taste, which consists mainly of non-volatile compounds.

Aroma is one of the critical aspects of tea quality which can determine acceptance or rejection of a tea before it is tasted. There are more than 630 compounds have been reported responsible in tea aroma.

The three basic types of tea; green, oolong and black have different quality characteristics, including aroma, taste and color, and appearance.

All of these aromas are generated from four main pathways: carotenoids as precursors, lipids as precursors, glycosides as precursors, and Maillard reaction pathway.

Carotenoids are important precursors of tea volatile compounds, especially the C9- to C13-aromas. Ionone and damascone are important C13-carotenoid-derived compounds that constitute an essential aroma note in black tea.

Tea contains many amino acids, but theanine, specific to the tea plant, is the most abundant, accounting for 50% of the total amino acids. Amino acid degradation is involved in the biogenesis of the tea aroma. Chlorophyll, carotenoids, lipids and volatile compounds are not major constituents in a tea brew but they also play an important role in the development of the aroma.

During black tea processing, including withering, rolling and fermentation, the lipids are degraded to produce flavor volatiles by hydrolytic or oxidative action of enzymes on glycolipids and phospholipids.

The major fatty acid derivatives include alcohols, aldehydes and lactones. C6 and C9 alcohols and aldehydes are key contributors to the “fresh green” odor of tea. Methyl jasmonate, an important fatty acid derivative, is a major contributor to the jasmine-like aroma of oolong tea.
Volatile compound responsible for aroma of tea

Characteristics of Darjeeling black tea

Darjeeling in India produces very famous teas with its own characteristic aroma and color. An exceptional, light, golden tea with a delicate taste form one of the world’s finest growing regions, Darjeeling is regarded as the Champagne of teas.

Normally characterized as having bright color, and delicate, with a fresh vibrant and distinctive muscatel character, thin body and an evident astringency, the aromatic profile of Darjeeling tea is highly revered for its ethereal quality, a reason why these teas fetch record prices in tea auctions.

For the connoisseur, Darjeeling is best enjoyed black due to its light and delicate nature.

The aroma of Darjeeling teas is between two types of tea, Keemun (aroma: rosy and woody note) and Uva (sweet flower-like fragrance).

The pleasant flowery notes of linalool oxides have been especially observed in high-quality Darjeeling black tea. Darjeeling tea also contains high geraniol and it so considered to be genetic characteristic.

It has been estimated that the tea of Darjeeling contains three times higher amount of volatiles than does Assam orthodox tea. Moreover, the content of monoterpene alcohols is about five times higher in Darjeeling tea as compared to the plain North-east Indian tea.

Darjeeling black teas undergo a much lighter and more delicate fermentation process compared with other black tea: the leaves are almost semi0oxidised which can often be seen by the mixture of black, golden and light brown leaves with hints of green noticeable in a fine quality Darjeeling.
Characteristics of Darjeeling black tea

Essential oil of tea leaves

Tea has a unique fresh aroma. The aroma that the tea leaves give off comes across in the tea infusion. This fragrance is also referred to as the ‘nose’ of the tea.

It is generally believed that the characteristic of various kinds of tea consist of a balance of very complicated mixtures of aroma compounds in tea.

Aromas of compounds differ according to the variety of tea, and more than six hundred different aroma compounds are found in tea.

It is quite clear that the aroma of the fermented tea has to be quite different from the aroma of green tea.

Tea leaves contain a volatile oil consisting of alcohols, aldehydes, phenols and some fatty acids.

Fresh tea leaves have a somewhat grassy smell, and the refreshing fragrances of young leaves and flower similar to lily of the valley and rose are apparent.

Some of aroma compounds identified in fresh tea leaves are mostly alcohols, including Z-2-penten-1-0l, n-hexanol, Z-3-hexen-1-ol, E-2-hexen-1-ol and linalool plus its oxides, nerol, geraniol, benzylalcohol, 2-phenylethanol, and nerolidol.

The aroma of Japanese green tea, especially first crops of spring, is characteristically refreshing with a green note caused by (Z)-3-hexenyl-(E)-2-hexenoate and hexenoate.

Main aroma components of black tea are alcoholic comp sounds such as linalool, linalool oxides, geraniol, benzyl alcohol, 2-phenylethanol, while in oolong tea, jasmine lactone, nerolidol and indole are the most abundant aroma component.

Linalool and its oxidized derivatives namely linalool oxides are the main constituents of black tea aroma. In some aroma Assam black tea, the content is as high as 60%.
Aroma compounds in tea leaves

Aroma of tea

The custom of drinking tea has spread all over the world. The aroma is the major factor contributing to tea quality and enjoyment.

The freshly picked green leaves of the tea plant require processing in order to induce the formation of the characteristic odor and flavor of tea. Various aroma compounds develop during withering and fermentation stages of tea leaves.

The formation of tea aroma during the four main stages of manufacturing: beginning with fresh green leaf stage through the withering stage, fermenting stage after rolling, and finally in the made tea stage flowing firing.

Floral tea aroma compounds are known to be generated during the fermentation process in the tea manufacturing and is one of the most important factors to determine the quality of each tea type, especially oolong and black tea.

Research into characterizing tea aromas has been carried out for past 100 years, and more than 600 volatile compounds had been reported or isolated.

The most important of these are: limonene, phenylethyl alcohol, linalool, geraniol, trans-2-hexenal, phenylethyl acethyldehyde, alpha and beta-ionone, isovaleric acid, benzoic acid, o-cresol, dimethyl disulfide and n-ethylformyl pyrrole together with 18 esters and lactones.
Aroma of tea

Aroma of tea leaves

Tea has a unique fresh aroma. The aroma that the tea leaves give off comes across in the tea infusion. This fragrance is also referred to as the ‘nose’ of the tea.

Aromas of compounds differ according to the variety of tea, and more than three hundred different aroma compounds are found in tea.

Tea leaves contain a volatile oil consisting of alcohols, aldehydes, phenols and some fatty acids. On steam distillation, black tea gives an essential oil. The characteristic aroma and flavor of tea is due to the essential oil.

The aroma of Japanese green tea, especially first crops of spring, is characteristically refreshing with a green note caused by (Z)-3-hexenyl-(E)-2-hexenoate and hexenoate.

Green tea has more of the aroma of fresh tea leaves, because of reduced enzymatic reactions during manufacturing process.

Fresh tea leaves have a somewhat grassy smell, and the refreshing fragrances of young leaves and flower similar to lily of the valley and rose are apparent.

Main aroma components of black tea are alcoholic comp sounds such as linalool, linalool oxides, geraniol, benzyl alcohol, 2-phenylethanol, while in oolong tea, jasmine lactone, nerolidol and indole are the most abundant aroma component.

The aroma complex of tea varies with the countries of origin. Slight changes in climate factors can result in noticeable changes in the composition of the aroma complex.
Aroma of tea leaves

The Flavor of Tea

The Flavor of Tea
The principal components which determine the aroma, flavor and physiological action of tea are:

• An essential oil: about 0.5%, this is probably formed during fermentation.

• Caffeine: 1.8 to 5.9%

• Tannins: 13 to 18%

Some 140 components have been reported as contributing to the aroma and flavor of tea and research in this field is continuing.

The aim of making good tea is to obtain the maximum extraction of caffeine and the minimum amount of tannins. Most commercially available teas are blends, designed to satisfy the tastes of the customer. One would think that making a cup of coffee would be quite a simple matter. This is far from so; there are many schools of thought as to how this should be done. These range from the very elaborate and formalized ritualistic proceedings of the Japanese tea cult, to homely brew which is being increasingly appreciated around the world.
The Flavor of Tea