Tea Harvest Season and Its Quality
In Wazuka, tea can be harvested three times in a year. The tea plant is a perennial evergreen tree. Under suitable climatic conditions, it continuously produces new leaves. However, because Japan experiences winter, harvests cannot be done year-round. Depending on the region in Japan, tea can be harvested 3 to 4 times a year. In Wazuka Town, tea is harvested three times a year: in spring (late April to May), summer (June to July), and autumn (September to October). In warmer, tropical regions, tea can be harvested four times a year.
Winter Makes Japanese Tea Taste Better
During Japan's harsh winter, tea plants enter dormancy. From autumn to winter, and from winter to early spring, the tea plant absorbs and stores nutrients from the soil. This is why the new buds harvested in spring are rich in amino acids, making them delicious. The presence of four distinct seasons in Japan is crucial for Japanese tea, which places great importance on umami (the savory taste).
Harvest Time and Quality
The quality of tea varies greatly depending on the harvest season. The first flush harvested in spring has the highest amino acid content of the year. Spring tea leaves are tender and thin, and they are even delicious when eaten raw. In contrast, autumn leaves are thick and tough.
(First flush harvested in spring)
(Tea leaves harvested in autumn)
The figure above shows the differences in amino acid and tannin content between the first flush (ichibancha) and third flush (sanbancha). The amino acid content is higher in the first flush, while tannin, which contributes to bitterness, is more abundant in the third flush. In other words, the first flush has a strong umami flavor, while the umami decreases and bitterness increases in the second and third flushes.
The Importance of Harvest Timing
Even within the same harvest season, it is crucial to harvest at the optimal time. As the leaves grow, the amino acid content decreases. This is particularly noticeable in the first flush, where the amino acid content changes significantly over time. If the tea is harvested too late, the amino acid content will be lower, the leaves will become tougher, and the tea quality will drop. Therefore, it is important to harvest on the right day to ensure the best quality.
Figure 1: Changes in Component Levels by Harvest Time
Anan et al.; Tea Technology Research Institute (1974)
Harvest Timing: One Bud and Two Leaves
Generally, tea is harvested when the top bud and two small leaves, known as isshin-niha (one bud and two leaves), are ready. The ideal time is when the top bud begins to open. If harvested too early, the umami compounds haven't fully developed in the leaves, resulting in a tea with a weak flavor. In reality, the exact timing for harvesting can vary from year to year, so it is crucial to carefully assess the situation based on experience.
Tea Amino Acids Convert to Catechins Under Light
Tea contains amino acids, the majority of which are theanine. The diagram below shows the estimated pathway from theanine to catechins. Light controls the conversion of theanine to catechins through the A-ring pathway. Therefore, in the presence of light, the synthesis of catechins, which contribute to bitterness, is promoted from theanine.
Figure: Biosynthesis Pathway of Catechins (Estimated)
Ryokyo Saijo, "The Flavor of Tea 1) Biosynthesis and Chemical Changes of Catechins" (1994)
Cover cultivation can prevent the conversion of amino acids into catechins
Tea grown under cover benefits from the protective effect of the cover, which helps prevent the decrease in amino acid content. This is one of the reasons for growing shaded tea, such as matcha and kabusecha. On the other hand, unshaded teas like sencha experience a faster decrease in amino acids, so the harvest window is shorter, and it becomes more critical to precisely determine the right time to harvest compared to matcha.
Figure: Changes in Components Due to Shading
Anan et al.; Tea Technology Research Institute (1974)
