Emma Wilson
Mushrooms are a type of fungus that can be cultivated or found growing in the wild. They are a popular food item, but they can also be poisonous and cause severe illness or even death if consumed without proper knowledge. The dangers of mushrooms are not limited to those that are inherently poisonous, but also include those that have been contaminated by bacteria, mould, or pests during the cultivation or storage process. Contamination can occur due to improper sterilisation, overhydration, or other factors, and it can lead to the growth of harmful bacteria such as Salmonella, Listeria, and Staphylococcus spp. Therefore, it is crucial to be able to identify contaminated mushrooms and take the necessary precautions to avoid any potential health risks associated with their consumption.
| Characteristics | Values |
|---|---|
| Common contaminants | Bacteria, mould (fungi), pests, trichoderma, orange bread mould, cobweb mould |
| Common sources of contamination | Incorrect sterilization, human vectors, impurities in air, soil or water |
| Signs of contamination | Discolouration, sectoring, slimy patches, dustiness, powder-like substance on top of mycelium |
| Contaminated mushrooms dangerous? | Yes, contaminated mushrooms can cause food poisoning and, in some cases, hospitalization. |
| Preventing contamination | Proper sterilization, pasteurization, sanitation, air filtration, substrate sterilization, good sterile technique, proper cleaning |
| Preventing food poisoning | Proper handling, washing, preparation, storage, cleaning |
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What You'll Learn
- Common contaminants include trichoderma, mould, bacteria, and pests
- Contaminated mushrooms can cause food poisoning and hospitalisation
- Mushrooms can become contaminated during growth or post-harvest
- Contaminated mushrooms may cause hallucinations, liver toxicity, and seizures
- Preventing contamination requires sterile technique and equipment
Common contaminants include trichoderma, mould, bacteria, and pests
Mushrooms are vulnerable to a wide range of contaminants, which can be separated into three groups: bacteria, mould (fungus), and pests. Bacteria are unicellular microorganisms that reproduce quickly and can be dealt with by pasteurising and sterilising the substrate. Mould, on the other hand, is a type of fungus that grows in the form of filaments called hyphae and can be controlled with salt, baking soda, alcohol, or cinnamon. Lastly, pests are tiny insects that devour the mushroom culture and transmit diseases.
One common bacterial contamination is cobweb mould, which is not a single species but a group of closely related mould species that cause soft rot in mushrooms. Cobweb mould thrives in high humidity and stagnant air, so lowering the humidity and increasing air circulation can help limit its growth. Another common contaminant is trichoderma, a group of green mould fungi present in all soils. Trichoderma can be treated by spreading salt on the affected area, though it is often better to simply discard the contaminated mushrooms and sanitise the affected area.
Other common contaminants include orange bread mould and bacterial contamination on grain, which can sometimes be separated from healthy grains if the contaminated patch is small and contained. To accomplish this separation, use an alcohol-sanitised or flame-sterilised spoon to scoop out the contaminated area. Additionally, spore contamination can be fatal to the entire culture, while contamination during the fruiting phase can lead to cap removal.
To reduce the chances of contamination, it is important to maintain a sterile environment and properly prepare and sanitise substrates. This includes practising good sterile technique, ensuring clean working conditions, and using air filtration to keep the environment rich for the mycelium and free of competitors such as bacteria, mould, and pests. However, these methods are not foolproof, and contaminants can still flourish in sterilised substrates due to the absence of competition, which is naturally present in wild-growing mushrooms.
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Contaminated mushrooms can cause food poisoning and hospitalisation
Mushrooms are a type of fungus that can be found growing in the wild. While some mushrooms are edible, others are poisonous and can even be deadly. It is recommended that you only eat mushrooms purchased from a reputable source, such as a supermarket or greengrocer. Wild mushrooms should only be consumed if they have been identified as safe by a mushroom expert (mycologist).
Mushrooms that are not properly handled, washed, prepared, or stored can cause food poisoning. Mushrooms can become contaminated with harmful bacteria if they are grown on compost or fertiliser that has not been properly sterilised, or if they come into contact with raw meat, poultry, or seafood. Consuming contaminated mushrooms can lead to food poisoning, and in some cases, hospitalisation.
Symptoms of mushroom poisoning include severe gastrointestinal upsets such as abdominal pain, nausea, vomiting, and diarrhoea. These symptoms can occur within 6 to 24 hours of ingesting poisonous mushrooms. In some cases, mushroom poisoning can lead to liver and kidney damage, and death can occur within 48 hours. It is important to seek medical attention immediately if you suspect that you or someone in your care has eaten a poisonous mushroom, even if symptoms have not yet appeared.
To prevent food poisoning from mushrooms, it is important to follow proper food handling and cleaning techniques. This includes washing hands and utensils with warm water and soap before and after handling mushrooms, and storing fresh mushrooms in the refrigerator. Mushrooms can be gently cleaned with a damp cloth or a soft-bristled mushroom brush, or rinsed under cool running water and patted dry.
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Mushrooms can become contaminated during growth or post-harvest
To limit the chances of contamination, growers must ensure that their grains or substrates are not overhydrated. Overhydration leads to high humidity, which, coupled with stagnant air, creates an ideal environment for cobweb mould to grow. A laminar flow hood is the best way to reduce undesired spores and other airborne contamination in the workspace. It is, however, a costly system. A more affordable option is a still air box, which is popular for small-scale projects and home cultivators.
Substrate sterilization and air filtration are other ways to keep the environment sterile and rich for the mycelium, but free of competitors such as bacteria, mould, or pests. However, these methods are not foolproof, and contaminants can spread very quickly. Therefore, it is advised to get rid of contaminated cultures and separate them from the non-contaminated ones.
Mushrooms can also become contaminated post-harvest. If not properly handled, washed, prepared, and stored, mushrooms can cause food poisoning. They can become contaminated with harmful bacteria if they are grown on compost or fertilizer that has not been properly sterilized. Mushrooms can also be contaminated through cross-contamination with raw meat, poultry, or seafood during packaging and storage. Storing fresh mushrooms unrefrigerated in an airtight container may also promote the growth of harmful bacteria that could cause botulism.
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Contaminated mushrooms may cause hallucinations, liver toxicity, and seizures
Mushrooms are a type of fungus that can be found growing wild or cultivated. While some mushrooms are edible, others are poisonous and can even be deadly. It is recommended that only store-bought mushrooms are consumed, as there is no home test to distinguish between edible and poisonous mushrooms. However, even store-bought mushrooms can be contaminated with harmful bacteria, leading to food poisoning.
Mushroom poisoning can cause severe gastrointestinal issues, such as abdominal pain, nausea, vomiting, and diarrhea. In some cases, it can also lead to hallucinations, liver toxicity, and seizures. For example, the species Psilocybe, Gymnopilus, and Panaeolus produce compounds that can cause hallucinations and altered sensorium. Additionally, the toxin in the death cap mushroom (Amanita phalloides) can harm the liver and kidneys, and death can occur within 48 hours of ingestion.
The risk of mushroom poisoning can be mitigated by proper handling, washing, preparation, and storage. Mushrooms should be washed gently with cool running water or a damp cloth before use. It is important to practice good hygiene and clean utensils, countertops, and cutting boards before and after handling mushrooms to avoid cross-contamination.
Furthermore, it is crucial to recognize the signs of mushroom poisoning and seek immediate medical attention. Symptoms of poisoning can include gastrointestinal issues, hallucinations, liver and kidney damage, and seizures. If a person has collapsed, stopped breathing, or is having a seizure after consuming mushrooms, emergency services should be contacted right away.
In summary, contaminated mushrooms may cause hallucinations, liver toxicity, and seizures, among other serious health issues. It is important to properly identify mushrooms before consumption and practice good food safety practices to minimize the risk of poisoning.
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Preventing contamination requires sterile technique and equipment
Preventing contamination in mushroom cultivation requires a sterile environment and processes. The ideal growing conditions for mushrooms are, unfortunately, also ideal for other unwanted fungi, including moulds. Moulds are the biggest competitor to the mushroom grower. Therefore, it is of utmost importance to follow sterile techniques and implement prevention methods to minimize the risk of contamination.
To prevent contamination, it is crucial to identify the possible sources of contamination. The air is a very likely source of contamination for mushroom growers. Mould spores and other contaminants, although invisible to the naked eye, are everywhere, just waiting to ruin your project! The best option to reduce contaminants in the air is to use a laminar flow hood, which includes a filter pad, fan, and a HEPA (High-Efficiency Particulate Air) filter. The system is costly but worth the investment for medium to large-scale culture plate work and liquid culture inoculations. If a flow hood is not in your budget, a still air box is another option to reduce airborne contaminants.
Water can also usher in bacteria, fungi, viruses, and other malevolent microorganisms into the delicate growing environment. Mushroom growers should use sterilized water that is free from contaminants to prevent waterborne contamination. Using reverse osmosis systems and UV light sterilization can help ensure the purity of the water.
The substrate used in mushroom cultivation can also introduce contaminants to the growing environment. Mushroom growers should use high-quality substrates that are free from contaminants. Sterilized substrates can obliterate undesirable microorganisms, while the incorporation of fungicides and other chemicals can safeguard against contamination. Before inoculating with a mushroom culture, the bulk substrates and grains should be completely sterilized. This means subjecting the substrate or grain to high pressure and temperature for an extended period.
Human handling can also introduce contaminants to the growing environment. Mushroom growers should maintain proper hygiene and use personal protective equipment such as gloves, masks, and hairnets when handling mushroom cultures.
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Frequently asked questions
Mushrooms contaminated with pathogenic bacteria have caused outbreaks across the U.S. and Canada. If ingested, this will cause the same symptoms as the diseases caused by the bacteria, including food poisoning and, in some cases, hospitalization. The common culprits responsible for mushroom-related outbreaks are soil bacteria like Listeria, Staphylococcus, and Salmonella.
A healthy mushroom culture will run through grain or other substrates reasonably uniformly. If you notice any sectoring—where borders form and hyphae refuse to merge—you could be dealing with contamination from another fungal species. Discoloration is another sign of contamination. Changes in colour, such as yellow or brown spots or streaks on the surface of the mushrooms or growing medium, may indicate contamination.
To prevent contamination, it is important to follow good sterile technique and ensure that your growing environment is sterile. This includes properly preparing and sterilizing your substrates and ensuring you are as clean as possible before working with sterile substrates.
