Most people who go looking for information about mold in coffee find Ochratoxin A first. It is the name in every article, the bogeyman in every supplement-side coffee brand’s marketing, and the toxin the European Union has actually bothered to regulate.
It deserves the attention. It is also more mundane than the worst of the internet would have you believe.
This is what Ochratoxin A is, where it comes from, what the science actually says about its health effects, what regulatory bodies have done about it, and what to look for if you want a coffee that has been honestly tested for it.
What it is
Ochratoxin A (OTA) is a secondary metabolite produced by several species of mold, principally Aspergillus ochraceus, A. carbonarius, A. niger, and Penicillium verrucosum. “Secondary metabolite” is the technical term for a compound a fungus produces that does not serve its primary metabolism. It is, in other words, an industrial byproduct of a mold doing its work on a substrate. That substrate, in the case of coffee, is the coffee cherry as it ferments and dries after harvest.
OTA is chemically a chlorinated isocoumarin connected to a phenylalanine residue by an amide bond. The structure makes it stable. It survives roasting. It survives brewing. It does not survive the human kidney unscathed, which is the part that matters.
Once consumed, OTA is absorbed primarily through the small intestine, distributed via blood plasma where it binds tightly to serum albumin, and accumulates in the kidneys. Its plasma half-life in humans is approximately 35 days, which is unusually long for a small molecule and is part of what makes chronic low-dose exposure a regulatory concern rather than an acute risk.
Where it comes from in coffee
Coffee cherries ripen on the tree in tropical and subtropical climates. After picking, they are processed (washed, natural, or honey methods) and dried. The drying step is the critical window. Aspergillus species like warm, humid environments and moderate moisture content. If cherries are dried on the ground in inconsistent weather, if drying beds are not raised, if storage warehouses run humid, the molds settle in. By the time the green coffee reaches a buyer, the molds may be long gone, but the OTA they left behind is not.
The risk is not uniform across origins. A 2010 review in Food Additives and Contaminants noted that OTA prevalence in green coffee correlates strongly with post-harvest handling practices, regardless of country. Well-managed cooperative-style washing stations produce green coffee that consistently tests low. Bulk commodity coffee from variable supply chains tests across a much wider range.
Robusta coffee tends to test higher than arabica on average, in part because much of the world’s robusta is grown in regions and conditions with less consistent post-harvest infrastructure. Decaf does not test inherently higher or lower than caffeinated coffee. The starting green coffee is the variable that matters.
What the research says about health effects
The honest version of this story has more nuance than the supplement-coffee marketing copy.
OTA is classified by the International Agency for Research on Cancer as Group 2B: possibly carcinogenic to humans. The 2B classification means there is sufficient evidence of carcinogenicity in animal studies and limited or inadequate evidence in humans. Other Group 2B substances include carpentry work, pickled vegetables, and gasoline engine exhaust. The classification is meaningful but it is not the same as the Group 1 classifications applied to aflatoxin B1, tobacco smoking, or asbestos.
Animal studies have shown OTA to be nephrotoxic (kidney-damaging), hepatotoxic at higher doses, immunosuppressive, and teratogenic. Long-term exposure in rodents produces renal tumors. The dose-response curves established in those studies are the basis for the regulatory limits enforced in the European Union.
In humans, the strongest associations are with kidney pathology. Balkan Endemic Nephropathy, a chronic kidney disease historically observed in rural areas of the former Yugoslavia and Bulgaria, has been linked epidemiologically to dietary OTA exposure, though aristolochic acid is now considered the more likely primary cause. Chronic Interstitial Nephropathy in Tunisia has shown similar epidemiological links. These conditions involve exposures considerably higher than typical Western consumption.
The European Food Safety Authority, which regulates the EU’s coffee limit, established a tolerable weekly intake of 120 nanograms per kilogram of body weight in 2020, based on the nephrotoxic threshold. A 70-kilogram adult, on that basis, has a tolerable weekly intake of 8,400 nanograms, or 8.4 micrograms. For context, a cup of brewed coffee made from coffee at the EU regulatory limit of 5 µg/kg (roasted) at a typical 12-gram dose contains roughly 60 nanograms of OTA. Many cups a day, every day, would be required to approach the tolerable threshold on regulator-compliant coffee.
The interpretation is this: the acute risk from a cup of mainstream-compliant coffee is small. The chronic-exposure question for people who drink several cups a day, every day, for decades, with no information about what is in any of those cups, is the legitimate basis for the transparency conversation.
What regulators actually require
The European Union enforces a maximum level of 5.0 micrograms per kilogram of Ochratoxin A in roasted coffee and 10.0 µg/kg in green coffee, under Regulation (EU) 2023/915. The limit was tightened from 8.0 µg/kg in earlier versions of the regulation as analytical methods improved.
The United States does not enforce a regulatory maximum for OTA in coffee. The FDA monitors aflatoxins but has not set an OTA action level for coffee. Canada, Switzerland, and several other markets have set their own limits, generally aligned with or stricter than the EU.
The practical effect: coffee sold into European markets is tested at the importer level, generally on a sampling basis, against the 5 µg/kg roasted limit. Coffee sold purely into the US market may or may not be tested by anyone in the supply chain. Some specialty roasters test voluntarily. Most do not.
What we tested and what we found
In October 2025, our roasting partner Lineage Roasting shipped a green coffee sample of our decaf to Eurofins Central Analytical Laboratories in New Orleans. Eurofins ran the assay under ISO/IEC 17025:2017 accreditation using LC-MS/MS, the gold-standard analytical method for OTA. The result returned on 31 October 2025: less than 2.0 µg/kg. Below the laboratory’s limit of detection.
The Eurofins report number is AR-25-QA-100167-01. We covered the methodology and the full result set, including aflatoxins, in our pillar post: Is Your Decaf Tested for Mold? Most Aren’t.
The 2 µg/kg detection floor is significant because it is calibrated 2.5 times tighter than the EU’s roasted coffee limit. A green coffee that reads below 2 µg/kg before roasting will, after the 50-80% reduction roasting typically produces, end up far below any regulatory threshold in any market in the world.
This is one batch. Specialty coffee analytical labs like Eurofins are increasingly offering ongoing per-batch programs, and that is the direction we are moving. Until then, one assay, one published result, one number.
What to look for if you care
A short list.
- ISO 17025-accredited lab reports, not “tested” claims on the bag. The accreditation is what makes the result auditable.
- Sample-specific reports with sample IDs, methods, and dates. Generic “we test for mycotoxins” pages without published reports are marketing, not data.
- Roasters that test green coffee, not roasted. Roasted-coffee tests are useful but green-coffee tests catch problems before they enter your supply.
- Methodology mentioned by name. LC-MS/MS for Ochratoxin A. USP 561 or AOAC methods for aflatoxins. If the brand cannot name the assay, the brand may not actually have one.
- Frequency of testing. A single result is a snapshot. A program is a posture. Roasters that test every lot are operating on a different standard than roasters that tested once.
The conversation about mold in coffee will keep getting louder as more brands publish data and as regulators in the US consider whether to follow the EU’s lead. The right side of that conversation, as a consumer, is the side that asks for evidence and reads the report.
Frequently Asked Questions
Is Ochratoxin A in all coffee? Ochratoxin A is detectable in a significant percentage of commercial coffee samples, with prevalence varying by origin, processing method, and post-harvest handling. The European Union enforces a 5.0 µg/kg regulatory limit for roasted coffee, and most coffee sold into EU markets tests below that level. US markets have no equivalent limit, so testing depends entirely on the roaster’s voluntary practices.
Does decaf have more Ochratoxin A than regular coffee? Decaf is not inherently higher in Ochratoxin A than caffeinated coffee. The starting green coffee determines the OTA level, not the decaffeination process. Some research suggests water-based decaffeination methods may reduce surface contamination, but the primary factor remains the quality of the green coffee.
What is the safe limit for Ochratoxin A? The European Food Safety Authority established a tolerable weekly intake of 120 nanograms per kilogram of body weight in 2020. The European Union enforces a 5.0 µg/kg maximum level in roasted coffee. The United States does not set a regulatory limit for OTA in coffee.
Can I remove Ochratoxin A from coffee at home? No. Ochratoxin A is heat-stable and not removed by brewing, filtration, or home processing. The only way to ensure low exposure is to source coffee from suppliers who test for it and publish results.
Is Heist coffee tested for Ochratoxin A? Heist’s green decaf was tested by Eurofins Central Analytical Laboratories in November 2025 under ISO 17025 accreditation. The result was below the lab’s limit of detection at less than 2.0 µg/kg, 2.5 times below the EU’s regulatory limit for roasted coffee.
What to read next
- Is Your Decaf Tested for Mold? Most Aren’t.. The pillar post with our full Eurofins data and methodology.
- The Four Mycotoxins You Should Care About in Coffee. The broader category, not just OTA.
- The Science Behind Decaf Methods. Water, ethyl acetate, methylene chloride, and why the process matters.
No Curfews is the editorial dispatch from Heist, a coffee company that thinks the second half of the day deserves better. We publish lab results, sources, and the occasional opinion. Join the list if this is the kind of thing you want in your inbox.