Where does the honey scent in tea come from?

The honey-like aroma in Oriental Beauty tea and Darjeeling black tea traces back to two compounds: 2,6-dimethyl-3,7-octadiene-2,6-diol and 3,7-dimethyl-1,5,7-octatriene-3-ol. Japanese scholar Akio Kobayashi identified these as the core sources in work that began in 1990, when he analyzed Oriental Beauty tea made from leaves fed upon by the smaller green leafhopper and compared it with oolong and black tea.

Feeding by the green leafhopper triggers abnormal metabolism in the tea plant, which produces special compounds that summon natural enemies as a defense. Kobayashi found linalool and its derivatives far more abundant in Oriental Beauty tea than in ordinary oolong or black tea, with 3,7-dimethyl-1,5,7-octatriene-3-ol present at several times those levels. The compounds are known; how they form is not.

Where does the unique honey-like aroma of honey-scented tea actually come from? Since the 1990s, Japanese scholar Akio Kobayashi has gradually unveiled the mysteries of the aroma components of Oriental Beauty tea and Darjeeling black tea, discovering that two substances—2,6-dimethyl-3,7-octadiene-2,6-diol and 3,7-dimethyl-1,5,7-octatriene-3-ol—are the core sources of the honey-like flavor. Even more astonishing is that after a tea plant is fed upon by the smaller green leafhopper, it actually initiates abnormal metabolism to produce special compounds, summoning natural enemies to defend itself. This article will guide you through an in-depth understanding of the scientific discoveries regarding the aroma components of honey-scented tea, as well as the fundamental differences in aroma characteristics between Darjeeling black tea and Taiwan black tea.

What exactly are the components that make up the signature aroma of honey-scented tea? This question has long puzzled tea farmers, tea merchants, and consumers. As for how these components are generated and which biochemical pathways and mechanisms are involved, the scientific community has so far only solved the first half of the puzzle—the characteristic chemical components of natural honey fragrance have been identified, but their formation process and generation mechanism still await further investigation. The first scholar to devote himself to the study of honey-scented tea aroma was Akio Kobayashi of Japan. In 1990, he used Oriental Beauty tea made from tea leaves fed upon by the smaller green leafhopper (Empoasca onukii Matsuda) to analyze its aroma composition, and compared it with oolong tea and black tea that had not been fed upon by the smaller green leafhopper. The research revealed two major characteristics of Oriental Beauty tea's aroma: First, the content of linalool and its derivatives (linalool I, II, III) is extremely abundant, far higher than that of ordinary oolong tea, with the content of linalool I and linalool II being nearly 1 to 10 times that of oolong tea and black tea. If we look at the ratio of total linalool derivatives to linalool, Oriental Beauty tea's ratio is significantly higher, reaching 2 to 10 times that of ordinary oolong tea and black tea. Second, Dongfang Meiren tea contains a large amount of 3,7-dimethyl-1,5,7-octatriene-3-ol, with content more than 3 to 20 times higher than that of oolong tea and black tea. Akio Kobayashi speculated at the time that this was very likely the characteristic aroma component of Oriental Beauty tea, and that it could only be produced through tea leaves fed upon by the smaller green leafhopper, but this had not yet been clearly confirmed.

In 1996, Akio Kobayashi and his colleagues once again conducted research on the characteristic aroma components of honey-scented tea. This time he compared Oriental Beauty tea and Indian Darjeeling black tea, both of which had been fed upon by the smaller green leafhopper and both of which carried a honey-like flavor, as well as other black teas that had not been fed upon by the smaller green leafhopper and did not have a honey-like flavor. The results showed that the greatest common characteristic of the aroma components of the honey-flavored Oriental Beauty tea and Darjeeling black tea was that both contained extremely abundant 2,6-dimethyl-3,7-octadiene-2,6-diol, with Oriental Beauty tea having a particularly prominent content; conversely, tea that had not been fed upon by the smaller green leafhopper had very little of this component. This component is regarded as the key reason why Oriental Beauty tea and Darjeeling black tea exhibit a muscat flavor. In addition, the content of 3,7-dimethyl-1,5,7-octatriene-3-ol in Oriental Beauty tea and Darjeeling black tea is also quite high. In short, there are currently two recognized characteristic components of honey fragrance: 2,6-dimethyl-3,7-octadiene-2,6-diol and 3,7-dimethyl-1,5,7-octatriene-3-ol. The former is the product of abnormal metabolism in tea leaves after being fed upon by the smaller green leafhopper, while the latter is generated from the former through dehydration reactions during processing or other manufacturing stages. Akio Kobayashi's research showed that the 2,6-dimethyl-3,7-octadiene-2,6-diol contained in Oriental Beauty tea is far higher than that in Darjeeling black tea, which is also fed upon by the smaller green leafhopper. Many other studies on Darjeeling black tea aroma have also pointed out that Darjeeling black tea contains high levels of monoterpene compounds, which is the most significant difference between it and Assam black tea. Among the more than 600 aroma components of Darjeeling black tea that have been identified, it has now also been confirmed that 2,6-dimethyl-3,7-octadiene-2,6-diol and 3,7-dimethyl-1,5,7-octatriene-3-ol are the signature components of Darjeeling's honey fragrance.

Honey-scented tea not only has a unique aroma, but also embodies nature's exquisite survival wisdom—why do tea buds that have been fed upon by the smaller green leafhopper produce this special honey-scented chemical component? In recent years, Chen Zongmao and others at the Tea Research Institute of the Chinese Academy of Agricultural Sciences have explored the chemical information associations among tea plants, pests, and natural enemies, unraveling the mystery of why tea buds produce 2,6-dimethyl-3,7-octadiene-2,6-diol after being fed upon by the smaller green leafhopper. It turns out that nature follows the law of "natural selection, survival of the fittest," or more precisely, this is akin to the Chinese saying, "The mantis stalks the cicada, unaware of the oriole behind."

After the smaller green leafhopper feeds on tender tea buds, the tea plant, in order to grow and survive, may have undergone hundreds or even thousands of years of evolution, with the tender tea buds producing the special component 2,6-dimethyl-3,7-octadiene-2,6-diol through an abnormal metabolic pathway. At extremely low concentrations, this component can attract the natural enemy of the smaller green leafhopper—the white-striped jumping spider (Evarcha albaria)—luring the natural enemy to prey on the smaller green leafhopper, allowing the tea buds to continue growing. In other words, the tea plant produces this special component through abnormal metabolism to call for help from natural enemies to defend itself. Chen Zongmao and others also confirmed that if artificial insect needles are used to simulate the chewing and piercing-sucking damage of the smaller green leafhopper to tender tea buds (i.e., mechanical damage), the tea plant will indeed release some volatiles, but the components produced differ from those under actual feeding damage by the smaller green leafhopper; however, if the oral secretions of the smaller green leafhopper are extracted and applied dropwise to mechanically needle-damaged tender buds, then 2,6-dimethyl-3,7-octadiene-2,6-diol will likewise be produced. This shows that the oral secretions of the smaller green leafhopper are the true trigger that induces tender tea buds to produce this special honey-scented component.

The above content is compiled by CoffeeHunters, a coffee news website.