Does Brewing Method Change Mycotoxins in Your Cup? What the Lab Studies Found

By Mike Cullen, Founder · Published October 28, 2026

Key takeaway: Yes, a little. In one lab study, espresso carried about half as much ochratoxin A from the grounds into the cup, moka pot about a third less, and auto-drip only about 15% less. Drip passed most of it through. Brewing helps at the margins, but the biggest lever is starting with clean, tested beans.

Here's a question we get from the lab-report crowd (our favorite crowd): if a little mold toxin made it into the beans, does the way you brew change how much ends up in your mug?

Scientists have actually measured this. The short version: your brewer matters a bit, your beans matter a lot.

What are mycotoxins, and which one do coffee studies track?

Mycotoxins are compounds some molds can produce on crops, especially when they're dried or stored badly. In coffee, the one researchers study most is ochratoxin A, usually shortened to OTA. Aflatoxins get tested too.

If you want the full background, start with our guide to mycotoxins in coffee and what "mold in coffee" really means.

Does OTA actually make it from the grounds into the cup?

A good chunk of it, yes. OTA dissolves in hot water well enough to follow your coffee into the mug.

• A Swiss team at ETH Zurich found OTA "eluted into the brew," detecting it in 18 of 40 brews made from store-bought coffees (Studer-Rohr et al., Food Chem Toxicol 1995).
• A Brazilian study tested the transfer directly. The drip method extracted about 86% of the OTA in the ground coffee, and a traditional Brazilian cloth-style brew extracted about 74%. The difference between the two wasn't statistically significant (Leoni et al., Food Addit Contam 2000).

So you can't count on your coffee maker to leave it behind in the filter.

Which brewing method lets the least OTA through?

The most direct comparison comes from the University of Navarra in Spain. Researchers roasted contaminated beans, then brewed them three of the most common European ways and measured OTA in the cup (Pérez De Obanos et al., Food Addit Contam 2005).

That drip number lines up nicely with the Brazilian study: most of the OTA in drip grounds ends up in the cup.

The authors' conclusion was that "the method of coffee brew preparation plays a key role" in how much OTA people actually take in.

Why would espresso carry less OTA than drip?

The study measured the difference, it didn't pin down the reason, so treat this part as an educated guess. Espresso uses far less water and a much shorter contact time than drip. A brew that pulls less of everything from the grounds will likely pull less OTA too.

Which ties in with a fun fact from our espresso vs drip caffeine deep dive: espresso is concentrated, but a big mug of drip extracts more total stuff from more coffee.

What about French press, cold brew and Turkish coffee?

The research gets thinner here.

• A University of Valencia study looked at 21 mycotoxins across coffee-maker, electric machine, instant and traditional Turkish preparations. Several, including OTA, showed significant differences between brewing methods. The authors concluded that coffee intake didn't represent a potential risk for consumers for any individual mycotoxin they measured (García-Moraleja et al., Food Chem Toxicol 2015).
• We didn't find a solid head-to-head study measuring OTA transfer in French press or cold brew, so we won't guess a number. If one turns up, we'll update this post.

Curious how those brews compare on other things? See filtered vs French press vs espresso and cold brew vs hot coffee.

Does roasting matter more than brewing?

Roasting is the bigger step down, and it starts before you ever touch a brewer.

• In the same Navarra study, roasting cut OTA by a mean of 66.5%, though the reduction was uneven from batch to batch (Pérez De Obanos et al., 2005).
• An Italian study found roasting reductions depended on how intense the roast was, with espresso-style roasts showing reductions of more than 90% in the samples tested (Romani et al., J Agric Food Chem 2003).
• A Qatar University study of traditional roasting followed by brewing found OTA dropped about 59 to 65%, while aflatoxins dropped about 40 to 62% depending on roast (Al Attiya et al., PLoS One 2021).

Notice the pattern: roasting and brewing each reduce some of it. Neither reliably removes all of it.

So what's the smartest move?

Start clean, then brew however you love.

1. Pick beans with published lab results. Brewing only trims what's already there. Learn to check any report with how to read a coffee lab report.
2. Store beans dry and sealed. Moisture is mold's best friend. Our coffee storage guide covers it.
3. Then brew for flavor. Espresso, drip, moka, pour-over: once the beans are clean, choose what tastes best to you.

That's exactly why we test before we roast. Every lot of Pure Health Coffee is tested by Eurofins, and our posted sample reports showed no detectable mycotoxins, including ochratoxin A below 1 ppb on our 2024 green-bean report. You can see them yourself on our lab results page and read what we test for on our mold-free coffee page. Results apply to the samples tested.

It's a Peruvian single-origin Arabica, medium roasted, with notes of chocolate, caramel and roasted nuts. I started Edge in St. Paul in 2020 so I could brew any way I want without wondering what's in the beans. These days that's drip on weekdays and a moka pot on Saturdays.

FAQ

Does brewing coffee remove mycotoxins? Partly. In a University of Navarra study, the brewed cup had about 15% less ochratoxin A than the grounds with auto-drip, about 32% less with a moka pot and about 50% less with espresso. None of the methods removed it completely.

Does espresso have fewer mycotoxins than drip coffee? In that same study, espresso carried less ochratoxin A from the grounds into the cup than auto-drip did. Results depend on the beans, though, so clean starting beans matter more than the brewer.

How much ochratoxin A gets into drip coffee? Most of it. A Brazilian study found the drip method extracted about 86% of the OTA present in the ground coffee, and the Spanish study found only about a 15% reduction with auto-drip.

Does roasting or brewing reduce mycotoxins more? Roasting usually does more. Studies found roasting reduced OTA by roughly 66% on average in one study and more than 90% for espresso-style roasts in another, with results varying by batch and roast level.

Does cold brew have fewer mycotoxins? We didn't find a solid study measuring ochratoxin A transfer into cold brew, so there's no reliable number yet. Starting with tested beans is the dependable approach for any brew method.

What's the best way to limit mycotoxins in coffee? Choose coffee that publishes lab results for mycotoxins, store beans dry and sealed, and then brew whichever way you enjoy.

This article is general information about coffee and food-safety research. Results from individual studies apply to the samples they tested.

Sources

1. Pérez De Obanos A, González-Peñas E, López De Cerain A. Influence of roasting and brew preparation on the ochratoxin A content in coffee infusion. Food Addit Contam. 2005;22(5):463-71. https://pubmed.ncbi.nlm.nih.gov/16019819/
2. Leoni LA, Soares LM, Oliveira PL. Ochratoxin A in Brazilian roasted and instant coffees. Food Addit Contam. 2000;17(10):867-70. https://pubmed.ncbi.nlm.nih.gov/11103271/
3. Studer-Rohr I, Dietrich DR, Schlatter J, Schlatter C. The occurrence of ochratoxin A in coffee. Food Chem Toxicol. 1995;33(5):341-55. https://pubmed.ncbi.nlm.nih.gov/7759018/
4. García-Moraleja A, Font G, Mañes J, Ferrer E. Analysis of mycotoxins in coffee and risk assessment in Spanish adolescents and adults. Food Chem Toxicol. 2015;86:225-33. https://pubmed.ncbi.nlm.nih.gov/26514696/
5. Romani S, Pinnavaia GG, Dalla Rosa M. Influence of roasting levels on ochratoxin A content in coffee. J Agric Food Chem. 2003;51(17):5168-71. https://pubmed.ncbi.nlm.nih.gov/12903986/
6. Al Attiya W, Hassan ZU, Al-Thani R, Jaoua S. Prevalence of toxigenic fungi and mycotoxins in Arabic coffee (Coffea arabica): Protective role of traditional coffee roasting, brewing and bacterial volatiles. PLoS One. 2021;16(10):e0259302. https://pubmed.ncbi.nlm.nih.gov/34714880/
7. Edge Coffee sample Eurofins report AR-24-JF-015481-01 (Pure Health Coffee green beans, Mar 2024), via /pages/lab-results