What Really Determines Matcha Quality?

Many explanations of premium matcha begin with two claims: the tea should be grown under a traditional overhead shade structure, and the leaves should be dried in a traditional tencha furnace. Both methods have real value. The problem begins when they are treated as if they automatically guarantee more theanine, more amino acids, better taste or proportionally higher chemical quality.

Tea is an agricultural product. Long before a leaf enters a tencha factory, its composition has already been influenced by genetics, season, soil and nutrition, shading, weather, leaf maturity and the exact day of harvest. Processing can preserve, transform or sometimes reduce parts of that potential, but it cannot make the starting leaf irrelevant.

1. Four layers that determine matcha quality

A useful way to think about matcha quality is to separate four layers that are often mixed together in marketing.

For chemical composition, the first two layers deserve much more attention than they usually receive.

2. Shelf shading vs direct shading: what does the research actually show?

Traditional shelf shading keeps the covering material above the tea canopy, while direct shading places the material close to or directly on the plants. Shelf systems cost more to build and operate, and they allow growers to manage a long shading period without the covering material resting on the shoots.

An important 2019 report from the Aichi Agricultural Research Center examined tencha produced under shelf shading and direct covering. The study was designed to distinguish the two production systems. Interestingly, the researchers reported that a digital color index (the percentage of green pixels, or GR value) separated the two groups more accurately than conventional chemical analysis such as total nitrogen and amino acids, or sensory evaluation such as appearance, aroma and taste.^[1]

The charts in that report also show substantial overlap between the groups in total nitrogen and sensory scores. Shelf-shaded samples tended to extend into the higher end of the distribution, so it would be wrong to say that the methods are identical. But it is equally difficult to defend the idea that the shading label alone cleanly predicts chemical or sensory quality.

Another study from Fukuoka demonstrates how sensitive shaded tea can be to the conditions immediately before harvest. After the shade was removed from gyokuro shoots, six hours of exposure reduced free amino acids from roughly 3,858–3,891 mg/100 g to 3,203 mg/100 g and theanine from roughly 2,583–2,610 mg/100 g to 2,169 mg/100 g, while total catechins increased to 9.8%.^[2] This is a reminder that when and how a leaf is exposed to light can matter directly to its chemistry.

3. Traditional tencha vs simplified tencha: processing is important, but it is not the whole story

Traditional tencha is steamed and dried without the rolling steps used for sencha. A dedicated tencha furnace is designed to dry the spread leaves in stages. In contrast, what is often called simplified tencha or moga-cha in production regions can be made by adapting existing green-tea machinery and minimizing rolling so that the dried leaf can be used for powdered tea.

Kumamoto Prefecture has published a production method using an existing steamed green-tea line to make powder-tea raw material continuously. In those trials, first-flush material produced the best color among the tested seasons, and the prefecture concluded that good-quality powder-tea raw material could be produced with the adapted line.^[3]

That does not mean that a simplified line is equivalent to a traditional tencha furnace. Traditional tencha drying can contribute to aroma formation. Research from Shizuoka followed dimethyl sulfide (DMS), an important component associated with the characteristic aroma of shaded tea, through a tencha furnace. DMS increased markedly in the later drying stages and in the finished crude tencha.^[4]

So the better scientific question is not “Which label is superior?” but:

4. Our own data: a result that challenged our assumptions

At Sanrokuen, we purchase and analyze tea from multiple growers in Kumamoto. Our commercial data are not a controlled scientific experiment, but they provide a useful real-world test of the assumption that more expensive, more traditional processing automatically means a higher analytical score.

The striking point is not merely that one inexpensive tea scored 104. The lowest first-flush simplified-tencha score in our dataset was 44, while the 2026 traditional organic tencha scored 35. The median simplified-tencha score was 75.2.

In other words, in our actual purchasing and analysis, “traditional tencha” did not mean “higher analytical score.” And a five-fold difference in purchase price certainly did not produce a five-fold difference in measured composition.

5. Why the 2026 Seimei result is especially interesting

The 2026 organic tencha was not an obviously weak raw material. It was made from Seimei, a cultivar specifically developed for matcha and powdered tea, and it was carefully grown by a producer whom we regard as one of Kumamoto's leading tea growers.

NARO (Japan's National Agriculture and Food Research Organization) describes Seimei as having strong suitability for shaded tea, good color, relatively high amino acids—especially theanine—and weaker bitterness and astringency compared with Yabukita.^[5] NARO's comparative data are particularly revealing because Seimei maintained higher theanine than Yabukita across several processing systems. In the published examples, Seimei vs Yabukita theanine was 4.99 vs 3.34 g/100 g in conventional tencha-machine processing, 3.56 vs 2.34 in a newer tencha line, and 2.87 vs 1.55 in pan-fired processing.^[5]

This does not mean cultivar explains everything. It means the chemistry of the raw material has a strong genetic component that remains visible across different processing approaches.

That makes our three-year result—26 in 2024, 44 in 2025 and 35 in 2026—even more useful as a reality check. A respected producer, a cultivar known for matcha quality, organic cultivation and traditional tencha processing still did not automatically produce a high AF score every year.

6. Kumamoto's grading system may have taught growers to produce for measurable quality

There may be a specifically Kumamoto background behind the strong simplified-tencha scores we see. For years, some premium Kumamoto teas have been evaluated under the “Yūga no Kokochi” (湧雅のここち) grading system, which combines explicit chemical-composition standards with sensory quality evaluation. This gives growers a measurable target—not only an abstract instruction to “make better tea.”

This matters because a grading system can change how farmers learn. When total nitrogen, free amino acids, theanine, fiber and tannin are measured year after year—and when those values are connected to a recognized quality grade—growers can compare results, adjust field management and gradually build practical knowledge about how to produce leaves with stronger analytical characteristics.

This does not prove that the grading system caused the score increase, nor that simplified-tencha processing creates higher component values. Weather, cultivar composition, harvest timing and many other variables changed from year to year. The important point is narrower: Kumamoto already had a production culture in which growers were repeatedly given chemical targets and feedback before the current matcha boom.

In other words, Kumamoto farmers did not suddenly begin learning how to produce amino-acid-rich tea when global matcha demand accelerated. Some had already spent years working in a system that explicitly rewarded high nitrogen, high free amino acids and high theanine, together with low fiber and tannin. It is reasonable to consider that accumulated know-how when evaluating today's Kumamoto matcha raw material.

The ideal next experiment would still be a controlled split-leaf trial: take fresh leaves from the same field, cultivar and picking date, divide them immediately, process one batch in a traditional tencha furnace and the other through a simplified-tencha line, then compare total nitrogen, free amino acids, theanine, catechins, fiber, color, aroma compounds and blind sensory scores.

7. What traditional methods still add

None of this is an argument against traditional matcha production. Shelf shading and dedicated tencha processing have real benefits that may justify higher prices.

Higher price can therefore represent labor, infrastructure, lower throughput, traditional craftsmanship, organic certification, scarcity and regional value—not just a higher concentration of amino acids.

8. If you care about taste and chemistry, judge the tea—not only the label

For serious buyers, cafés and matcha brands, we believe the most rational evaluation begins with the finished tea and the information behind the fresh leaf.

Conclusion

Research does not support a simplistic equation in which shelf shading automatically means much higher chemistry than direct shading, or traditional tencha processing automatically means much higher component values than simplified tencha.

The evidence is more interesting than that. Shading method affects the growing environment. Processing affects drying, color and aroma. But the leaf arrives at the factory with a chemical history already written by cultivar, season, nutrition, shading duration, maturity, weather and the grower's decisions.

Our own Kumamoto data reinforce that point. A carefully produced 2026 organic Seimei traditional-tencha lot scored 35 in our analytical evaluation, while first-flush simplified-tencha lots ranged from 44 to 104 with a median of 75.2. The organic traditional tencha cost approximately five times as much as the 104-point simplified-tencha lot.

Kumamoto's regional grading history adds useful context. Premium tea growers have worked with explicit targets for nitrogen, free amino acids, theanine, fiber and tannin for years. The five-year “Yūga no Kokochi” records are not proof of causation, but they are consistent with the idea that growers have been learning how to move measurable leaf quality in the desired direction.

That does not make simplified tencha “better.” It means “traditional tencha” and “expensive” are not chemical measurements—and that the grower's accumulated field knowledge may matter far more than a processing label suggests.

If the goal is to understand matcha's measurable composition and actual drinking quality, the most rational approach is to examine the fresh-leaf background, the finished tea, analytical data and sensory quality together.