Mycotoxins in Coffee: What the Data Say and How Roasting and Testing Help

If you've spent any time reading about coffee quality online, you've probably run into the word mycotoxins, often alongside some alarming claims. We test our coffee for them, so we have a stake in this topic. That's exactly why we want to give you the straight story: what researchers have measured, what roasting does, what the toxicology says, and what the evidence does not show.

What are mycotoxins?

Mycotoxins are toxic compounds produced by certain molds. They can turn up on many crops, and food-safety agencies around the world monitor them (WHO mycotoxins fact sheet).

The two most discussed in coffee are:

• Ochratoxin A (OTA): produced by certain Aspergillus and Penicillium molds. A 2024 review noted that coffee beans are particularly susceptible to OTA contamination (Banahene et al., Heliyon 2024). OTA can occur along the coffee chain, and good farm, drying, and storage practices help reduce it (López-Rodríguez et al., J Fungi 2024).
• Aflatoxins: a group of mycotoxins monitored in many foods (WHO), and also detected in some coffee products, as you'll see below.

How common are mycotoxins in coffee?

Ochratoxin A: found in about half of samples

A global systematic review and meta-analysis pooled 36 studies covering 3,182 coffee samples. OTA was found in about 53% of samples, with a pooled mean concentration of about 3.2 µg/kg. Levels varied widely by country, and OTA was more common in places with more annual rainfall and lower human development scores (Khaneghah et al., Fungal Biol 2019).

A second worldwide review, covering 40 studies and 3,256 samples, detected OTA in about 54.6% of samples. Average levels differed significantly between countries, continents, and coffee types (Massahi et al., Food Addit Contam Part A 2024).

Aflatoxins in instant coffee: one market's data

A 2025 study tested 84 instant coffees sold in China. Aflatoxin G2 was detected in about 89% of samples (mean 1.19 µg/kg), and T-2 and HT-2 toxins were found less often. Interestingly, OTA was not detected in any of those samples (Wang et al., Food Chem 2025). This is one market, so it may not reflect instant coffee elsewhere, but it's a reminder that results depend heavily on where and how coffee is produced.

What roasting does

Here's some genuinely good news: roasting substantially reduces OTA.

• A review of roasting studies found that most reported reductions of 60% or more in OTA. Researchers proposed three reasons: removal with the chaff, chemical conversion (isomerization) into a different form, and thermal breakdown (van der Stegen et al., J Agric Food Chem 2001).
• On an industrial production line, roast and ground coffee kept only about 16% of the OTA originally present in the green beans. Roasting was the main step that reduced it, mostly through thermal breakdown (Blanc et al., J Agric Food Chem 1998).

Both studies were carried out by coffee-industry researchers, which is worth knowing, but their findings line up with each other. Roasting reduces OTA a lot. It doesn't necessarily remove all of it, which is why the starting quality of green beans and testing still matter.

Why food-safety agencies take mycotoxins seriously

Mycotoxins aren't a marketing invention. Their toxicology, mostly from high-exposure situations and animal and lab studies, is well established:

• Aflatoxin B1 is classified by the International Agency for Research on Cancer as a Group 1 human carcinogen (WHO).
• High-dose aflatoxin exposure can be deadly. In a 2004 outbreak in rural Kenya, contaminated maize led to 317 cases of acute aflatoxin poisoning and 125 deaths (Lewis et al., Environ Health Perspect 2005). That was grain eaten as a staple food, not coffee.
• Ochratoxin A has its main toxic effect on the kidney, based largely on animal and cell studies (Khoi et al., Int J Mol Sci 2021), and it is classified as a possible human carcinogen (Group 2B) (Banahene et al., Heliyon 2024). WHO notes the human kidney link remains unclear (WHO).

Several countries regulate OTA levels in food products for exactly these reasons (Banahene et al., Heliyon 2024).

Where does exposure come from?

Coffee is only one dietary source. A small German biomarker study compared 36 vegans and 36 omnivores and found serum OTA levels about twice as high in vegans, linked to plant-based foods and to pasta and rice. Separately, levels of an OTA-related compound (2'R-OTA) were associated with coffee drinking (Penczynski et al., Mol Nutr Food Res 2022). It's a small study, but it shows that OTA exposure comes from a mix of plant foods, coffee among them.

What the evidence does not show

This part matters, and many articles skip it.

• We're not aware of any study linking mycotoxin levels in coffee to disease in people who drink coffee. The toxicology above comes from high exposures, other foods, and animal and lab research.
• The 2024 worldwide review estimated that daily OTA intake from all coffee types was below the tolerable intake values set by international expert bodies, and concluded that the OTA content of coffee is not toxic to consumers worldwide. It still recommended controlling mold growth along the supply chain (Massahi et al., 2024).
• Large studies of coffee drinking in general are, on the whole, reassuring. An umbrella review of more than 200 meta-analyses found coffee drinking was more often associated with benefit than harm (Poole et al., BMJ 2017).

So: mycotoxins in coffee are real and measurable, levels are usually low, and roasting reduces OTA substantially. This is a quality and testing topic, not a reason to fear your morning cup.

Why Edge tests anyway

If levels are usually low, why test? Because "usually" isn't a standard. Occurrence varies by region, climate, and handling (Khaneghah et al., 2019), and the experts who studied it recommend controlling mold along the chain (Massahi et al., 2024; López-Rodríguez et al., 2024). We'd rather verify than assume.

Our quality chain looks like this:

1. Source specialty-grade, organic, shade-grown beans from Peru's highlands.
2. Handle green coffee with attention to moisture and storage.
3. Roast in small batches for flavor.
4. Verify with third-party lab testing to our mold and mycotoxin specification.
5. Pack with nitrogen flushing to help preserve freshness.

That's a purity and quality choice for people who care what's in their cup. It isn't a health claim. Read our full testing standard and why we think tested coffee is worth choosing.

How to choose coffee with confidence

• Look for roasters who test and can explain what they test for.
• Favor specialty-grade beans, where defect standards are stricter. See what specialty grade means.
• Store your coffee cool, dry, and sealed after opening to protect freshness.

Ready for a tested cup? Explore Pure Health Coffee, All Day Decaf, or the full collection.

FAQ

Does coffee contain mycotoxins? Some does. Global reviews detected ochratoxin A in roughly half of coffee samples tested, usually at low levels (Khaneghah et al., 2019; Massahi et al., 2024).

Does roasting remove mycotoxins? Roasting reduces OTA substantially, by 60% or more in most studies reviewed, but not always completely (van der Stegen et al., 2001; Blanc et al., 1998).

Are mycotoxins in coffee dangerous? A worldwide review estimated OTA intake from coffee was below tolerable intake values (Massahi et al., 2024). We're not aware of studies linking coffee mycotoxins to disease in coffee drinkers.

Why does Edge test for mycotoxins? Because occurrence varies and we'd rather verify than assume. It's a quality standard. See how we test.

Educational food-quality content. Not medical advice.

Sources

1. WHO. Mycotoxins fact sheet. https://www.who.int/news-room/fact-sheets/detail/mycotoxins
2. Banahene JCM et al. Heliyon. 2024. https://pubmed.ncbi.nlm.nih.gov/39640601/ (doi:10.1016/j.heliyon.2024.e39313)
3. López-Rodríguez et al. J Fungi. 2024. https://pubmed.ncbi.nlm.nih.gov/39194915/
4. Khaneghah AM et al. Fungal Biol. 2019. https://pubmed.ncbi.nlm.nih.gov/31345415/ (doi:10.1016/j.funbio.2019.05.012)
5. Massahi T et al. Food Addit Contam Part A. 2024. https://pubmed.ncbi.nlm.nih.gov/39259858/ (doi:10.1080/19440049.2024.2400697)
6. Wang X et al. Food Chem. 2025. https://pubmed.ncbi.nlm.nih.gov/41202366/ (doi:10.1016/j.foodchem.2025.146949)
7. van der Stegen GH et al. J Agric Food Chem. 2001. https://pubmed.ncbi.nlm.nih.gov/11600012/ (doi:10.1021/jf0105586)
8. Blanc M et al. J Agric Food Chem. 1998. https://pubmed.ncbi.nlm.nih.gov/10554297/ (doi:10.1021/jf9707703)
9. Lewis L et al. Environ Health Perspect. 2005. https://pubmed.ncbi.nlm.nih.gov/16330360/
10. Khoi CS et al. Int J Mol Sci. 2021. https://pubmed.ncbi.nlm.nih.gov/34681895/ (doi:10.3390/ijms222011237)
11. Penczynski KJ et al. Mol Nutr Food Res. 2022. https://pubmed.ncbi.nlm.nih.gov/35072972/ (doi:10.1002/mnfr.202100874)
12. Poole R et al. BMJ. 2017. https://pubmed.ncbi.nlm.nih.gov/29167102/