Mold contamination in coffee is a common worry for many consumers, particularly as information about food contaminants becomes widespread. Mold is a fungus that can grow on agricultural products, leading to the production of toxic chemical byproducts called mycotoxins. Mycotoxins are a natural concern in any food supply chain, including coffee production. This article explores the reality of mold and mycotoxins in coffee and the health risk posed to the average consumer.
The Presence of Mold and Mycotoxins in Coffee
Mold spores are naturally present in the environment where coffee is grown, harvested, and stored. The raw green coffee bean is susceptible to contamination, especially in warm, humid climates typical of coffee-producing regions. Improper drying or storage conditions that allow for excessive moisture create an ideal environment for fungal growth.
Roasting kills the mold itself, but mycotoxins are stable compounds that remain in the coffee bean. Therefore, contamination is largely a function of poor agricultural handling and storage before the coffee reaches the roaster.
Assessing the Health Risks of Coffee Mycotoxins
The two mycotoxins most relevant to coffee are Ochratoxin A (OTA) and Aflatoxin, produced primarily by Aspergillus and Penicillium fungi. OTA is considered potentially harmful to the kidneys and classified as a possible human carcinogen. High exposure to Aflatoxin is associated with an increased risk of liver cancer.
The health risk is tied to the level of exposure, which is rarely high in commercially available coffee. Regulatory bodies worldwide monitor mycotoxin levels, and the human liver can neutralize low levels of these compounds. Studies show that consuming four cups of coffee daily accounts for only a small percentage (2% to 3%) of the maximum safe level established by international food safety authorities.
How Processing Reduces Mycotoxin Levels
The commercial coffee industry employs several controls to mitigate the risk of mycotoxins before the product reaches the consumer.
Initial Processing
The initial processing method, particularly wet-processing (washing), is effective at reducing mycotoxins in green beans. Dry-processed beans, where the fruit is left on the bean longer, tend to retain more OTA.
Roasting
The application of high heat during roasting is a primary defense against mycotoxins. Roasting causes significant thermal degradation of Ochratoxin A (OTA). Studies indicate OTA reduction ranges from about 15% in lighter roasts to over 90% in very dark roasts, while Aflatoxin levels are reduced by 42% to 55%.
Regulatory Oversight
Regulatory oversight further ensures safety, with agencies like the European Union setting strict maximum limits for mycotoxins in roasted coffee (e.g., 3.0 µg/kg for OTA). While the US does not have federally regulated limits for OTA, imported coffee is routinely monitored. Commercial levels are consistently maintained well below established international safety thresholds.
Consumer Steps to Ensure Coffee Safety
Consumers can take simple steps at home to prevent post-purchase mold contamination.
The most effective measure is proper storage, which requires keeping roasted beans in an opaque, airtight container. This container should be stored in a cool, dark, and dry location, as moisture and temperature fluctuations encourage mold growth.
It is advisable to purchase whole beans and grind them immediately before brewing. Pre-ground coffee has a much greater surface area exposed to moisture, making it more susceptible to contamination. Finally, regular cleaning of all brewing equipment, especially the water reservoir and grinder, is important to prevent mold accumulation.