How to Read a Matcha Certificate of Analysis (COA)

A matcha certificate of analysis (COA) is a lab report tied to one specific lot: it identifies the product, states when it was made and tested, and reports results across microbiological, contaminant, and physical-quality categories. It is not a guarantee about any lot that ships after it — a COA only speaks for the lot number printed on it, which is why reading one correctly means checking what it covers, who tested it, and whether it actually matches what's in front of you, not just whether it exists.

What a COA Is — and Isn't

A COA proves that a defined sample, drawn from a specific production run, was tested and returned certain results on a certain date. It does not prove that the next container off the same production line will test the same way, and it does not substitute for an ongoing relationship where lots are checked against each other over time. Nor does it cover a standing claim about the farm or process itself — an organic certification, for instance, is a separate document with its own scope and validity period, covered in organic matcha certifications and what they verify. That ongoing discipline — comparing successive lots against a retained reference sample across a full harvest cycle — is a different, complementary practice covered in how to evaluate matcha supplier consistency. This article is narrower: given one COA in hand, how do you actually read it and decide whether it supports what you're buying.

The Anatomy of a Typical COA

Formats vary by supplier and by lab, but a usable COA generally covers four kinds of information.

Identification block. Product name, lot or batch number, production date, and test date. This is the section to check first and most carefully — a COA is only meaningful if the lot number on it matches the lot number on your shipping documents and packaging. A beautifully detailed report attached to the wrong lot number tells you nothing about what you actually received.

Microbiological section. This reports results against common test categories: total plate count (a general measure of microbial load), yeast and mold, and pathogen screening (categories such as Salmonella or E. coli are typical, though which specific organisms are tested varies by lab and by destination requirement). What matters at this stage is recognizing the categories and confirming they were tested, not memorizing a pass threshold — acceptable levels are set by the regulator in your destination market, not by a universal matcha standard, so treat any specific number as something to verify with your own food safety authority rather than something to judge in isolation.

Contaminant section. This typically covers heavy metals (as a tested category — commonly lead, cadmium, and arsenic, among others depending on the lab) and pesticide residue screening. Some buyers, particularly in markets with specific import sensitivities, also request radionuclide testing as a distinct category. As with the microbiological section, the categories tested are what to check for; whether a given result is acceptable is a destination-market question, not something a COA states on its own.

Physical and quality parameters. Many suppliers also report moisture content, particle size, and sometimes color measurement (often expressed as an instrument reading rather than a simple description). These aren't safety parameters — they're quality parameters that affect shelf life, mouthfeel, and how the tea performs in your process, and they're useful for comparing lots against a specification even when they aren't regulated.

COA section	What it covers	What to check
Identification	Product name, lot number, production and test dates	Lot number matches your shipment; test date is close to production, not months stale
Microbiological	Total plate count, yeast and mold, pathogen screening categories	Which categories were actually tested, and against your destination's requirements — not a number in isolation
Contaminants	Heavy metals, pesticide residues, and sometimes radionuclide testing	Same categories tested consistently lot to lot; results verified against your destination regulator's limits
Quality parameters	Moisture, particle size, sometimes color measurement	Consistency against your own specification, since these aren't safety limits but do affect performance

How to Actually Evaluate a COA

Reading the numbers is only part of the job. A few checks matter more than the results themselves:

• Match the lot number to your shipment. Confirm the lot number on the COA appears on the packaging or shipping documents for what you actually received. A COA for a different lot — even from the same supplier and the same week — tells you nothing about the tea in front of you.
• Check who issued it. A supplier's in-house lab result is a reasonable routine document, but it reflects the supplier's own testing, not an independent check. A third-party accredited lab report carries more weight, particularly for a first order, a new supplier relationship, or an annual volume commitment where more is riding on the result.
• Check the test date against the production date. A COA tested close to production reflects the tea as shipped. One tested long after production, or with no test date stated at all, is harder to rely on.
• Compare against your destination market's requirements, not a generic standard. What counts as an acceptable result for heavy metals, microbiological counts, or any other tested parameter is set by the regulator in the market you're importing into. Confirm current requirements with your customs broker or your own food safety authority — a result that clears one market's threshold does not automatically clear another's.

Red Flags on a COA

A few patterns are worth pausing on rather than accepting at face value: a COA for a lot number that doesn't match what shipped; a COA with no lot number at all, or one that's illegible or clearly generic; results that are identical, to the decimal, across multiple different lots over time, which suggests a template rather than an actual test; and a supplier who resists or refuses a request for third-party testing, particularly on a first or trial order. None of these prove bad faith on their own, but each is worth a direct question before you rely on the document.

What to Agree with the Supplier Before You Need It

A few terms are worth settling early rather than negotiating after a shipment is already in question: whether a COA is provided per lot or only per production run (a production run can span multiple lots with more variation than one COA implies); who pays for third-party testing when you request it beyond the supplier's routine documentation; and what retest rights you have if a result looks inconsistent with prior shipments. Quality checkpoints before an annual matcha supply contract covers where these terms fit into a broader pre-signature verification sequence, including how to turn a documentation expectation into an actual contract clause rather than a verbal understanding.

Using the COA in the RFQ Conversation

COA expectations are worth raising before you place an order, not after the first shipment arrives with unexpected paperwork. How to write a practical RFQ for matcha sourcing covers stating your quality verification plan up front, including what documentation you expect alongside each shipment — naming COA depth and third-party testing expectations at that stage signals to a supplier that you intend to hold the relationship to a real standard from the start.

If you're evaluating a supplier's COA or want to build documentation requirements into an RFQ or contract, reach out to our team — we're a Japanese company that works directly with growers, and can match samples and quotes to your specification as you work through what documentation to expect.