matcha milling
process / process-matcha-milling
石臼挽き
Matcha milling is the step of grinding finished tencha into a fine powder with a tea mill or another device. The resulting particle size and mouthfeel differ by device (tea mill, ball mill, jet mill, and others).
On this page (6 sections)
Reading the bitterness
Matcha milling grinds finished tencha into a fine powder. The Urasenke explanation describes the traditional stone-mill method as 「仕上碾茶を石臼で挽き、抹茶になります」 (in translation: "Finished tencha is ground with a stone mill to make matcha"). Meanwhile, Sawamura and colleagues (2019) compared equivalent tencha ground in an electrically rotating granite tea mill, a ceramic ball-impact mill, and an ultra-high-speed air-impact jet mill. Their comparison indicates that devices other than tea mills are often used for processed-food applications, which are described as accounting for about 95% of matcha production.
A Shizuoka Prefecture demonstration trial (2016) notes that the 「抹茶」 (in translation: "matcha") used for sensory evaluation and component analysis was tencha powdered in a water-cooled metal mill, not a traditional stone mill. This is limited evidence that matcha milling is not necessarily confined to stone mills.
A 2022 glossary of taste terms for matcha judging from the Kyoto Prefectural Tea Industry Research Institute classifies 「過粉砕」 (in translation: "overmilling"), when a mill processes less tea per unit time than under standard conditions, as a quality defect accompanied by bitterness. Longer residence and heating of tea leaves inside the mill is described as producing 「火入れ味(焦げ味)」 (in translation: "heated flavor (burnt flavor)") accompanied by bitterness. The glossary treats bitterness as a defect due to overmilling and deterioration, rather than a desirable matcha characteristic. This is, however, an account based on judges' observations, not verification data from chemical analysis or a controlled sensory panel.
Sources for this overview
Checked for this overview: Used the Urasenke site's explanation of stone milling to support this paragraph.
粒度と食感からみた抹茶のおいしさ (The Mouthfeel of Matcha from the Viewpoint of Particle Size and a Texture)
Checked for this overview: Used Sawamura and colleagues' 2019 comparison of milling devices to support this paragraph.
Checked for this overview: Used the note on use of a metal mill in the Shizuoka Prefecture trial to support this paragraph.
抹茶の審査について (Sensory Evaluation of Matcha)
Checked for this overview: Used the account of bitterness arising from overmilling to support this paragraph.
Follow the connections
matcha →is processed by→ matcha milling
Structured claims — open a section to read each claim's confidence, evidence and limits
How processing and cooking change it (3)
Note: Matcha results from finely milling finished tencha with a stone mill or similar device. In research and food processing, however, metal mills, ball mills, and jet mills are also used.
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ingredient-matcha —is_processed_by→ process-matcha-millingScope: Taste-term explanation for matcha judging by the Kyoto Prefectural Tea Industry Research Institute (Table 6).
Note: The glossary positions 『苦味』 (in translation: "bitterness") as a quality defect from overmilling or deterioration, rather than a desirable characteristic peculiar to matcha.
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process-matcha-milling —has_perceived_bitterness_associated_with→ "Overmilling is a state in which the mill processes less tea per unit time than under standard conditions. Longer residence and heating of tea leaves inside the mill is described as producing heated flavor (burnt flavor) accompanied by bitterness."Scope: An unidentified Kyoto Prefecture test report cited in a footnote to Murakami (2022).
Note: The primary source for this claim is a test report cited as footnote †1 in Murakami (2022); we have not checked that original document. It is treated as preliminary because this is a secondary citation.
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process-matcha-milling —has_flavor_affected_by→ "Mill temperature. A mill normally warms to around 50°C during grinding, but matcha milled with the mill heated to 60°C has been reported to have a weaker taste aroma, a blander taste, and lower quality than under standard conditions."