What You Should Know About Mold in Coffee

Usually mold and mycotoxins found in beans are not enough to make you sick. But proper storage is important.

Some coffee contains mold and toxins — but should you be concerned? Videos circulating on TikTok with millions of views are stoking fear among java lovers.

The reality: Because of the multistep process involved in growing, harvesting and transporting coffee, it’s not uncommon for the coffee beans and grounds to contain fungus or mold. While mold typically grows on foods that we don’t store properly or are spoiled (like bread or cheese) you generally can’t control the presence of mold in coffee.

While the idea of sipping mold is not only gross, it may also be bad for you. Mold can produce poisonous substances called mycotoxins, and consuming foods or beverages with high levels of mycotoxins has the potential to make you sick, according to the U.S. Food and Drug Administration.

In the short term mycotoxin poisoning can cause gastrointestinal symptoms such as nausea, vomiting, or diarrhea. Long term, exposure to the toxins is associated with a variety of negative health outcomes, including a higher risk of liver and kidney cancer and harming immune function.

5 Things You Should Know About Mold in Coffee

But can you drink enough coffee for mold to be a true health concern? Here are five things you should know about coffee and mold.

1. Mold and Fungus Can Grow in Coffee That Isn’t Harvested or Stored Correctly

Certain molds and associated fungal toxins can be present in coffee because of factors like poor harvesting and processing practices, high moisture storage conditions, and where the coffee is grown, says Jae-Hyuk Yu, PhD, professor of bacteriology at the University of Wisconsin in Madison.

“To get coffee to mold, you generally need to expose it to some extra water,” says Christopher Hendon, PhD, assistant professor in the department of chemistry and biochemistry at the University of Oregon in Eugene, whose researches the chemistry of coffee.

“In our lab, we have experienced mold on occasion, but that is because we are deliberately submerging the coffee in water for several hours, and then exposing it to air for several days. That condition is unusual,” he says.

The No 1. rule for keeping coffee beans or ground coffee that you’ve purchased mold-free is keeping it dry, says Dr. Yu.

For the coffee home-brewer, the standard advice to “store in a cool, dry place” works well, says Dr. Hendon.

“Generally, you probably want to aim to consume the coffee you buy within a month — if only because the coffee loses its volatile organic compounds rapidly once ground and will no longer be enjoyable by then. And you’ll also minimize any risk of molding,” he says.

Volatile organic compounds (VOCs) in coffee, also known as odor compounds, are responsible for a coffee's sensory properties, such as its taste and aroma.

2. The Most Common Mycotoxins in Coffee Are Ochratoxin A and Aflatoxins

Ochratoxin A is a mycotoxin produced by certain Aspergillus and Penicillium molds. It’s been found in contaminated grains, such as wheat, rye, oat, and barley, as well as in coffee, grapes, and wine.

Aflatoxins are mycotoxins made by certain Aspergillus molds, and can be found in coffee, but is more common in peanuts, corn, and rice.

The U.S. Food and Drug Administration closely monitors the food supply chain to make sure that the levels of these toxins to make sure that the food (and coffee) people buy is safe.

The agency sets maximum levels of certain mycotoxins allowed in foods very low due to their severe toxicity. In the United States, aflatoxins are limited to 20 parts per billion.

There are no set maximum levels for ochratoxin A.

3. Lots of Coffee Contains Toxins, but Well Below Dangerous Levels

Samples of green coffee beans (unroasted) from Brazil showed that nearly all the samples — over 90 percent — were contaminated with mold, and 33 percent had low levels of ochratoxin A.

A study of Portugal roasted coffee bean samples found that 18 percent of samples analyzed contained ochratoxin A.

But the amount of toxins detected were still far below the level deemed safe.

In addition to the United States, many countries and health organizations (including the WHO) have set maximum allowable limits for mycotoxins in coffee to ensure safety, says Yu.

In rare cases, levels of ochratoxin A can still be present after roasting and may develop if the beans are not properly stored and dried, says Yu.

4. It’s Unclear if the Toxins in Coffee Actually Pose Risk to Human Health

The biggest risk of ochratoxin A is kidney damage, according to the World Health Organization. But most of the evidence of kidney toxicity and kidney cancer due to ochratoxin A exposure has been in animals — the association in humans is unclear.

A Spanish study in adolescents and adults that examined the risk of 21 different mycotoxins found in coffee concluded that drinking coffee didn’t pose any risks to health.

5. Brewing Coffee Further Dilutes the Toxins You May Consume

Hendon and Yu both agree that mold and any resulting toxins on coffee should not be a concern to java drinkers. Even in coffee where mold was detected, brewing the coffee diluted the concentration which lowers any health risk.

Caffeine also appears to help limit toxins- decaf coffee is more likely to contain ochratoxin A than caffeinated coffee, a study found.

“In coffee, the concentration of mold is extremely low. People should be more concerned with mold in their washing machines than in their morning brews,” he says.

The Takeaway

While ochratoxin A and aflatoxins can be found in coffee, the levels in commercially available coffee are generally kept within safe limits through quality control measures. And the brewing process further dilutes the toxins, so they’re unlikely to pose risks to your health. Storing your coffee in an airtight container to keep out moisture will keep your coffee safe and mold-free.

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