Mushrooms and Food Pathogen Risk
People have been eating mushrooms for centuries. As such, we have found newer and more effective ways to distinguish a safe-to-consume mushroom from a possibly harmful one. After all, mushroom toxicity has been known and studied for millennia, and is believed to have caused death in several historical figures.
Commercial farming of mushrooms ensures their safety, but only to a degree. Foraging for mushrooms remains a recreational endeavor, and misidentification of a poisonous species as edible can have detrimental effects on the consumers. Approximately 100 species of mushrooms are non-edible, and they can cause 6000 ingestions in the United States, mostly by children under six years, according to Tran and Juergens in 2020.
However, even the edible species may not be as safe as you think. Even if they don't produce harmful substances, some mushrooms are still not safe for consumption if they were mishandled or grown in fertilizer that was not properly sterilized. Without the proper temperature or pH for the processing of mushrooms, they may harbor harmful bacteria such as Salmonella, Listeria, or Staphylococcus spp.
What makes a mushroom toxic?
Some mushrooms naturally produce substances that may be toxic to humans when ingested. For instance, the species Psilocybe, Gymnopilus, and Panaeolus produce compounds called psilocybin and psilocin that can cause hallucinations, altered sensorium, and euphoria for 30 minutes to 2 hours. Other species like the members of the Cortinarius genus produce the nephrotoxic agent, orellanine that causes more serious manifestations like gastroenteritis and renal injury.
However, mushroom toxicity may not be due to the mushroom or their compounds at all. Contamination from water, animals, and improperly composted manure can make mushrooms unsuitable for consumption. Further, malpractices during and after harvests, storage, and transport, and cross-contamination from raw meat, poultry, or seafood in the refrigerators or counters at the grocery store can contaminate the mushrooms with harmful bacteria.
What are the potential risks associated with mushrooms?
Inedible mushrooms, with their released compounds alone, can cause several risks when ingested. The broad range of mushrooms that may be misidentified as edible may cause acute gastroenteritis, hallucinations, liver toxicity, nephrotoxicity, and seizures. However, the dangers do not stop there.
Mushrooms contaminated with pathogenic bacteria made headlines in recent years for causing outbreaks across the U.S. and Canada. If ingested, this will cause the same symptoms as the diseases caused by the bacteria. This will cause food poisoning and, in some cases, hospitalization.
Mushroom-related outbreaks
The common culprits responsible for mushroom-related outbreaks are soil bacteria like Listeria, Staphylococcus, and Salmonella. There have been many outbreaks of Listeria infection due to enoki mushroom consumptions in the past years. The most recent one was reported on March 10, 2020, where the public health and food regulatory agency, together with the CDC, identified Listeria via whole-genome sequencing as the causative agent for reported illnesses of 36 people from 17 states. Further, 4 deaths and 2 fetal losses were associated with the illness.
There were also reported outbreaks of Staphylococcal food poisoning since 1989 due to canned mushrooms. The first incidence was reported in the People's Republic of China (PRC) prompting recalls of mushrooms produced by canneries in the said country. The succeeding outbreaks were only a few months apart and were reported from different states — Mississippi, New York, and Pennsylvania. The cans associated with the outbreak in the United States had codes similar to the confirmed cases in PRC.
Salmonella also caused outbreaks in the U.K. and U.S. in 2001 and 2020, respectively. The first case was due to the presence of Salmonella in mushrooms, causing the U.K. Food Standards Agency to recommend consumers to wash and peel mushrooms before consuming them in their raw state. The latter case was due to dried wood ear mushrooms. 55 people from 12 states were infected, resulting in 6 hospitalizations. The outbreak was reported over in November 2020.
Food and Safety Tips for Mushrooms
Several organizations on Food Standards and Safety provided tips on how to eliminate or reduce the risk of pathogens in mushrooms. The most effective way is by partnering with a trusted laboratory for a thorough microbiological risk review combined with testing options for effective analysis of your products. Our teams work with our customers to select client-specific scientific testing solutions to ensure product safety for your consumers.
Also, responsible producers must follow practices that will ensure the freshness and safety of mushroom products. For instance, you need to ensure that your suppliers, from growers to transporters, follow the proper guidelines to reduce potential contamination. You can refer to the Mushroom Good Agricultural Practices (MGAP). For sanitation of the products, make sure to only use sanitizers approved by the U.S. Environmental Protection Agency (EPA). The proper sanitation sequence is as follows:
- Removal of the visible debris
- Pre-rinsing with water
- Application of the appropriate cleaner to remove the soils from the mushroom surfaces
- Thorough rinsing off of the cleaner
- Application of the sanitizer to decrease the microorganisms left after the cleaning process
- Air drying
Further, you need to proactively monitor and recognize potential risks on the product, in the growing environment, and in your packing/processing facilities so you can implement measures to prevent possible outbreaks.
Conclusion
Mushroom-related outbreaks are a serious matter, but with proper food handling, consumer education, and assistance from a reliable laboratory, you can ensure your consumers' safety and satisfaction with every mushroom purchase.
