Michael Davis
Dried mushrooms are a staple in many cuisines, but are they dangerous? Properly dried and stored mushrooms can last for months or even years, but if not dried or stored correctly, they can quickly spoil and grow harmful bacteria and mould. Some dried mushrooms have also been found to contain toxic trace elements such as mercury, cadmium, lead, and arsenic, which may be related to soil contamination. Cooking the mushrooms can reduce the levels of these toxic elements, but it is unclear by how much. Salmonella is also a concern with dried mushrooms, although it is unclear whether the drying process can generate salmonella or if it comes from external sources. Overall, while dried mushrooms can be a tasty and long-lasting ingredient, it is important to purchase them from reputable sources and practice proper storage and handling to minimize any potential risks.
| Characteristics | Values |
|---|---|
| Salmonella risk | Some sources claim dried mushrooms can contain salmonella, but studies have found no traces of salmonella in dried mushrooms. |
| Toxic trace elements | Some dried mushrooms contain Hg, Cd, Pb, and As, which can be reduced through cooking. |
| Foodborne diseases | Dried mushrooms have been linked to foodborne disease outbreaks, but the risk is generally considered low. |
| Storage | Dried mushrooms should be stored in airtight containers or vacuum-sealed bags to maintain potency and safety. |
| Shelf life | Properly stored dried mushrooms can last for months or even years. |
| Spoilage | Spoiled mushrooms can cause food poisoning, with symptoms like nausea, vomiting, and diarrhea. |
| Soaking | Dried mushrooms should be soaked before consumption to soften their texture and remove grit. |
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What You'll Learn
Salmonella and other bacteria
Salmonella is a type of bacteria that can cause food poisoning. Salmonella outbreaks have been linked to mushrooms, including dried mushrooms, even as recently as 2020. In September 2020, there was a multistate outbreak of Salmonella Stanley infections linked to dried wood ear mushrooms imported from China by Wismettac Asian Foods, Inc. of Santa Fe Springs, California. The product was recalled in the USA, and the US Food and Drug Administration recommended that all dried mushrooms should be reconstituted in boiling water to kill any pathogens. Salmonella can grow on decaying wood, so it is possible that the dried mushrooms were cultivated on or near chicken foraging grounds, which is where the contamination occurred.
Dried mushrooms can be safe to consume if they are properly handled, washed, prepared, and stored. It is important to follow good food handling practices to reduce the risk of contamination. This includes storing food properly, cooking it thoroughly, cleaning surfaces with soap and warm water, and practising good hand hygiene. Dried mushrooms should be stored correctly to prevent spoilage and the growth of harmful bacteria. They should be kept in a cool, dry place and can last for months or even years if stored properly.
Fresh mushrooms can also be a source of Salmonella if they are grown on compost that has not been properly sterilized or if they come into contact with raw meat, poultry, or seafood through cross-contamination. It is recommended to choose fresh mushrooms that are firm and avoid those that are bruised or show signs of spoilage. Fresh mushrooms should be refrigerated and eaten as soon as possible to prevent the growth of harmful bacteria.
In addition to Salmonella, other types of bacteria and toxins such as Staphylococcus, Listeria, and Staphylococcal enterotoxin have been linked to mushroom-related food poisoning outbreaks. In 1989, canned mushrooms from China were associated with an outbreak of staphylococcal food poisoning in the USA, affecting nearly 100 people. The outbreak was attributed to extensive handling of the mushrooms before canning, which created an opportunity for contamination. Proper canning processes and high hygiene standards are crucial to preventing the growth of harmful bacteria and toxins.
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Proper storage and handling
Firstly, it is important to ensure that mushrooms are completely dried within days of purchasing them. If they are not dried correctly, they will spoil quickly. You should feel the mushrooms for any soft spots, which could indicate bacteria or mould. If you notice a slimy texture, discard the mushrooms. Mushrooms should be firm, and any change in texture can indicate spoilage. A warning sign can also be an unusual smell. If the mushrooms don't smell earthy or neutral, this can indicate some sort of bacteria or yeast contamination. If the mushrooms emit a bad smell, throw them away.
Once dried, store the mushrooms in airtight containers or vacuum-sealed bags. Even when stored correctly, regularly check the mushrooms for any signs of deterioration, such as discolouration, unusual spots, or the presence of mould. Spoiled mushrooms can make you very sick due to mould and rot, which can creep in if not stored properly. Some common moulds that can grow on mushrooms include Penicillium or Aspergillus, which produce mycotoxins and can be dangerous to consume.
Before cooking with dried mushrooms, it is recommended to give them a quick rinse, then soak them until they have rehydrated. You can save the mushroom soaking water and add it to your dish, although the water from some types of mushrooms, such as Woodear, can taste unpleasant. It is important to rinse the mushrooms after soaking, as they can be gritty.
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Spoilage and food poisoning
Dried mushrooms can be a source of foodborne illnesses, including food poisoning, if not stored or prepared properly. Salmonella is a common concern with dried mushrooms, as they may be grown in conditions that come into contact with animal feces. However, it is important to note that proper drying and storage methods can effectively reduce the risk of pathogenic microorganisms.
When purchasing dried mushrooms, it is essential to choose reputable sources and practice safe handling and storage. Dried mushrooms should be stored in airtight containers or vacuum-sealed bags to maintain their quality and safety. Proper storage helps prevent the growth of harmful bacteria and moulds, which can cause food poisoning.
Before using dried mushrooms, it is recommended to give them a quick rinse and then soak them until they are fully rehydrated. Soaking not only softens the texture but also removes grit that may be present. The soaking water can be used in cooking, adding flavour to various dishes. However, it is crucial to discard any mushrooms that show signs of spoilage, such as discolouration, unusual spots, or the presence of mould.
Spoiled mushrooms can be dangerous and should not be consumed. Mould growth on mushrooms can produce mycotoxins, which are harmful to human health. Consuming contaminated mushrooms can lead to food poisoning, with symptoms including nausea, vomiting, and diarrhoea. Additionally, breathing in or ingesting mould spores can trigger allergic reactions or respiratory issues. Therefore, it is essential to regularly check dried mushrooms for any signs of spoilage and discard them if necessary.
Furthermore, certain species of dried mushrooms may contain toxic trace elements such as mercury (Hg), cadmium (Cd), lead (Pb), and arsenic (As). Cooking has been found to reduce arsenic levels in mushrooms, but the reduction in mercury, cadmium, and lead levels is less pronounced. It is important to consider the potential risks associated with consuming wild or dried mushrooms, especially those collected from areas with high environmental contamination.
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Toxic trace elements
Mushrooms can accumulate toxic trace elements, including mercury (Hg), cadmium (Cd), lead (Pb), and arsenic (As). Cooking mushrooms significantly reduces arsenic levels by 26-72%, while the reduction in levels of mercury, cadmium, and lead is much lower.
Mercury levels in Amanita ponderosa, Boletus edulis, Marasmius oreades, and Tricholoma georgii, as well as cadmium levels in some samples of Amanita caesarea and T. georgii, have been found to exceed legislated limits. Lycoperdon perlatum, Macrolepiota rhacodes, and Lepista nuda have been identified as large accumulators of lead, with a direct relationship between Pb concentrations in mushrooms and soil contamination due to traffic pollution. High arsenic concentrations have been reported in the genus Laccaria, although the bioconcentration factors are much lower than those of mercury and cadmium.
Studies on the effect of cooking indicate a decrease in the contents of these toxic trace elements after applying boiling or frying methods to fresh mushrooms. However, it is important to note that the reduction in levels of mercury, cadmium, and lead through cooking is lower compared to arsenic.
In terms of food safety, pathogenic microorganisms in dried mushroom products have led to recalls and foodborne disease outbreaks. Bacillus cereus (BC) has been detected in dried mushrooms, with contamination levels ranging from low to moderate. Proper drying and storage of mushrooms are crucial to maintaining their safety and preventing the growth of harmful bacteria and moulds.
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Country of origin
In the European Union, foods intended for sale to consumers must be labelled with information such as the name of the product, net quantity, nutritional value, storage recommendations, and country of origin. However, this does not define the maximum content of potentially toxic elements in dried wild-grown mushrooms. Studies have shown that wild mushrooms originating from Polish forests tend to contain higher contents of toxic elements compared to cultivated mushroom species.
In a study analysing the microbiological quality of 61 dried mushroom samples purchased online and in supermarkets, the country of origin was not provided for nine of the samples. The samples originated from China (33 samples), Bosnia and Herzegovina (6 samples), Bulgaria (5 samples), Spain (3 samples), Greece (2 samples), and Montenegro, Poland, and Vietnam (1 sample each).
Consumers should be aware of the potential dangers associated with consuming dried mushrooms, such as the presence of pathogenic microorganisms and toxic elements. While proper cooking can reduce the levels of some toxic elements, it is important to purchase mushrooms from reputable sources and follow safe handling and preparation practices.
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Frequently asked questions
Dried mushrooms are not dangerous if they are rehydrated and cooked before consumption. Cooking them helps to destroy the small amount of toxins present in the mushrooms.
Mushrooms can accumulate toxic trace elements such as mercury, cadmium, lead, and arsenic. Cooking the mushrooms significantly reduces the levels of arsenic in particular.
While it is rare, pathogenic microorganisms surviving in dried mushrooms have been known to cause foodborne disease outbreaks. Presumptive Bacillus cereus (pBC) was detected in 59% of dried mushroom samples in one study, but the contamination level was low.
