Oriental beauty tea is a well known tea in the tea world. Bite by insects, intense fruity/flowery and pronounced honeyed taste, this tea originally known to be cultivated in Taiwan (Hshinchu and Miaoli for example) sees its manufacture used for other countries, notably Muscatel teas in Darjeeling gardens. What gives this taste and what happens in the plant?
The steps involved in making Oriental Beauty are a bit different from the traditional cultivation steps for Taiwanese oolongs. As I am not an expert in this field, I will not be able to detail this part, but you have to keep in mind that there is a natural infestation of the fields by insects similar to grasshoppers before harvesting. This stage is mastered to avoid a bad growth or even the death of the tea trees and lasts a few weeks. Oriental beauty also undergoes a longer oxidation stage, resulting in green and more or less brown and red leaves (Cho et al. 2007).
What happens in a bitten leaf?
Briefly, to eat the leaves, the grasshoppers will secrete a saliva to partially break down the leaf. The local molecules of the leaf will be modified either directly by the bites or as a result of a defense reaction. Indeed, each stage of tea production can generate stress to the leaves such as plucking. The degree of biting would be an additional local stress before plucking since saliva can locally modify some structural or volatile molecules. How the plant reacts to this attack is yet another stress. It is therefore a balance between stresses that will generate the particular taste of oriental beauty, not just one or two stresses (Cho et al. 2007).
The leaf is a real chemical factory for the tea plant, for example to ensure photosynthesis (the growth of the plant). If the tea plant has too much leaf damage, it will not grow properly. The production of molecules in the tea plant will be completely modified, these molecules allow to fight against the attack of insects. These molecules will be located in the leaf or will be volatile. They can act as a natural repellent or as a protective agent against chemical degradation (Cho et al. 2007 and Liu et al. 2020).
In an organism, the production of molecules is governed by our genetic code. Environmental changes, in this case infestation, can alter how the genetic code will function. Thus, certain molecules will be produced in response to stress in favor of those normally produced. According to different studies on the chemical and genetic profile of oriental beauty leaves, thousands of genes function differently, which would be responsible for nearly a hundred molecules produced differently compared to other tea crops, including Taiwanese oolongs (Cho et al. 2007, Liu et al. 2020, Chien et al. 2020 and Mei et al. 2017).
For example, a class of molecules well represented in some oolongs, linalool, is more highly produced in oriental beauty in response to infestation because this molecule has a repellent role. This is allowed because the infested plant will produce more linalool synthase, a molecule responsible for linalool production (Mei et al. 2017). The types of linalool produced have not been studied in detail, but it has already been shown that each linalool would seem to impart a particular flavor such as floral, sweet, and creamy, which could explain a deeper, sweeter mouthfeel of beauty orientals (Wang et al. 1994).
The degree of infestation
In reality, in a field of oriental beauty, not all leaves are attacked by insects since a balance must be found between plant resistance and optimal production without irreversible damage. Chien et al. looked at infestation levels in oriental beauty fields ranging from 1-33%, 34-66% and 67-100%. Upon infusion of the leaves, the authors found that higher infestation resulted in greater production of molecules responsible for sweetness compared to low infestation. However, the overall production of molecules involved in stress resistance was greater, which means that heavily infested tea plants are more resistant to infestation but may be more vulnerable to further stress.
According to some growers, especially of muscatel teas, it seems that after several years of infestation cycles, tea bushes that are then not infested still naturally produce the same type of molecules as infested tea bushes. This raises several questions, especially if the adaptation to infestation is permanently installed in the genetic code of the tea plant.
Oxidation
Many other molecules are more or less produced during the infestation and also participate to the aromatic quality of the tea, these molecules will also be submitted to the more prolonged oxidation of the leaves. It also appears that the process of prolonged drying of the leaves leads to an accumulation of abscisic acid, a phytohormone that will lead to the production of other molecules that will produce or modify molecules in oriental beauty leaves (Cho et al. 2007). It would be very interesting to study the oxidation of oriental beauty in more detail as it would be just as important as the bites.