How to read a matcha certificate of analysis

What a COA is, and what it is not

A certificate of analysis is a report of tests done on a specific lot of matcha: a batch milled on a date, from a defined quantity of tencha, carrying one lot number. It tells you what was measured and what the results were. It is not a certificate of quality or taste, not an organic or halal certificate, and not a guarantee about any other lot from the same mill. A COA for lot A says nothing about lot B, which is why it should arrive with every shipment and why the lot number on the certificate must match the lot number on the bag.

In the Japanese tea trade the COA is usually produced by the mill or by a laboratory the mill commissions, and is passed down the chain. When we quote a lot we send its COA; when we ship it, the same COA travels with the goods. Our sample documents show a redacted example next to a product specification sheet, which is the other document you should read.

The header: lot, date, who tested

• Product name and lot number. Must match the bag label and the invoice. A COA without a lot number is a brochure.
• Milling or production date. Matcha is at its best within months of milling. A café should know whether what arrived was milled last month or last year; a COA with no date leaves you guessing.
• Who performed the tests. The mill's own laboratory, or an external laboratory, named. Both are normal in Japan. For microbiology, metals and pesticides, an external laboratory's name and the method give the numbers more weight; for moisture and particle size the mill's own instruments are standard.
• Test date. Pesticide and microbiology results should be recent and from the lot in question, not carried over from an earlier batch.

Physical lines: moisture, particle size, colour

Typical values, not legal limits. The spec sheet sets the lot's own targets; the COA shows whether the lot met them.

For a café, particle size is the most useful line on the page. A D50 under about 10 microns whisks smooth and holds in a latte; a lot at 20 microns or above will settle in an iced drink and feel gritty. The mill type is stated on the specification sheet rather than the COA; what the COA tells you is the result.

Microbiology

Matcha is a dried, heat-treated product and should carry very low microbial counts. A COA normally lists total plate count (general bacteria), coliforms or E. coli, yeast and mould, and a pathogen screen, usually Salmonella as negative in 25 g. Results are given as counts per gram or as not detected. For an importer these lines are what food safety officers look at first; for a café they confirm the powder was dried and stored properly. If any pathogen line reads anything other than negative or not detected, do not accept the lot.

Heavy metals

Tea takes up small amounts of metals from soil, and matcha is the whole leaf consumed, so buyers look at this section closely. A complete COA lists lead, arsenic, cadmium and mercury, each against a limit. Japan does not set a specific lead limit for tea, so Japanese COAs often quote the EU or Codex limits for comparison; results for Japanese matcha are typically well under them. What to check: that all four metals are listed, that the method and detection limit are stated, and that the result is a number or not detected, rather than a tick box.

Pesticide residues

This is the section that decides whether a lot clears customs in the EU, the US and Taiwan, and the one where a short COA is a problem. A proper residue report states how many compounds were screened, the method (usually LC-MS/MS and GC-MS), the limit of quantification for each, and the result per compound, with the legal limit of the market it was tested against. Three things to read:

1. Which market's limits. Japan's maximum residue levels for several tea pesticides are higher than the EU's and than US tolerances, and Taiwan runs its own list. A lot that passes Japanese limits can fail EU or Taiwan limits for the same compound. Ask which rulebook the report was checked against.
2. How many compounds. A Japanese multi-residue screen commonly covers a few hundred compounds; a report that lists ten is a partial screen.
3. Detected versus not detected. A detection below the limit is still a detection. For the EU, any residue of a compound with no EU authorisation is a problem even at low levels. Organic lots, such as Jun, Mori, Sawa and Daichi, usually show a page of not detected.

We send the current residue report with each lot and can run an EU-scope test on request. Tabi is tested to US tolerances specifically for that market, and Minami for Taiwan's border inspection; the country pages for the US and Taiwan explain why.

Radioactivity

Since 2011 many Japanese tea COAs include a radioactive caesium result (Cs-134 and Cs-137), tested against Japan's general food limit of 100 Bq/kg, which is stricter than the limits in the EU and the US. Results for tea from Kagoshima, Fukuoka and Shizuoka are reported as not detected. The EU dropped its remaining import conditions on Japanese food in 2023 and no destination we ship to currently requires the test for tea, but buyers still ask, and the mills still run it. It is a reassuring line, not a required one.

What is often missing, and what to ask for

• A lot number that matches the bag. Ask for it before accepting the shipment.
• A milling date. Ask; it is on the mill's records even when it is left off the certificate.
• Particle size. Many COAs skip it; the specification sheet should have it. If neither does, ask for a D50.
• The residue report's rulebook. Ask whether it was checked against your market's limits, and for an EU-scope or Taiwan-scope test if not.
• Caffeine and theanine. Rarely on a COA; occasionally on a spec sheet. Nice to have for a menu, not a safety line.

Read the COA against the specification sheet: the spec sets what the lot should be, the COA shows what it is. The buying guide lists the four spec-sheet lines to ask for alongside it, and if you want to see both before you order, request samples and ask for the documents for the lots you pick.

Questions buyers ask