John Miller
Mushrooms are a type of fungus that has been consumed by humans for centuries, dating back to prehistoric times. They are valued for their rich taste and meaty texture, and in some cases, psychotropic properties. While mushrooms are commonly incorporated into various dishes, they are also known for their ability to oxidize and change colour, particularly when cut, bruised, or cooked. This phenomenon, specifically observed in certain species like Psilocybe mushrooms, has sparked curiosity and led to investigations into the underlying chemical reactions. The oxidation process in mushrooms results in the development of blue coloration, which has been attributed to the presence of compounds such as psilocybin and psilocin.
| Characteristics | Values |
|---|---|
| Mushrooms that oxidize | Psilocybin-containing mushrooms, Boletales mushrooms |
| Reasons for oxidation | Oxidized gyrocyanin, pulvinic acid, psilocybin oxidation products, oxidation of phenolic compounds |
| Effects of oxidation | Blue coloration, staining |
| Preventing oxidation | Sauteeing mushrooms separately, removing gills, using oyster or shiitake mushrooms |
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What You'll Learn
Why do magic mushrooms turn blue?
Magic mushrooms or Psilocybe are fungi that produce the psychotropic compounds psilocybin and psilocin. They are one of several species that instantly develop a blue coloration when they are cut or bruised. This phenomenon has puzzled chemists for decades, but recent research has shed some light on the mystery.
The blue colour in magic mushrooms is caused by the oxidation of psilocybin, resulting in colourful indigo-like polymers. Psilocybin is a psychotropic compound found in certain species of mushrooms, such as Psilocybe semilanceata and Psilocybe mexicana. It can be ingested by consuming the fresh or dried fruit bodies, preparing herbal tea, or combining it with other foods to mask its bitter taste.
The oxidation of psilocybin in magic mushrooms was first observed by Swiss chemist Albert Hofmann in 1958 when he isolated psilocybin and psilocin from Psilocybe mexicana. However, the nature of the pigment and the biochemical pathway producing it remained unknown until recently. Dirk Hoffmeister from the Leibniz Institute for Natural Product Research and Infection Biology in Germany and his team have been studying this phenomenon for several years.
Using advanced analytical techniques, Hoffmeister and his team discovered that the pigment responsible for the blue colour is not a single compound but a complex mixture of linked psilocybin oxidation products. They identified six mushroom pigments that are products of a cascade reaction starting with psilocybin. This reaction involves the removal of a phosphate group from psilocybin by a phosphatase enzyme, converting it into psilocin. An oxidising laccase then creates psilocyl radicals, which combine to form C-5 coupled subunits and further polymerise via C-7.
While the exact function of the blue pigments is still unknown, Hoffmeister hypothesises that they may serve a protective role, acting as an on-demand repellent against insects or other predators. The compounds may produce reactive oxygen species, which are toxic to any insects feeding on the mushrooms. This hypothesis adds to our understanding of the complex chemistry and defence mechanisms of magic mushrooms.
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Oxidation of phenolic compounds in mushrooms
Mushrooms are a rich source of phenolic compounds, which are aromatic hydroxylated compounds. Phenolic compounds have been shown to possess antioxidant, anti-inflammatory, and antitumour properties, among other health benefits. The total phenolic content in mushrooms varies depending on the species, ranging from 1 to 6 mg of phenolics per gram of dried mushroom.
The antioxidant activity of phenolic compounds in mushrooms has been evaluated using various methods, including the Folin-Ciocalteau assay, colorimetric reaction with NaNO2 and AlCl3, and high-performance liquid chromatography. These assays help determine the total phenolic content and identify individual phenolic compounds present in the mushrooms.
Mushrooms with high phenolic content include the brown portobello mushroom, white cup mushroom, and shiitake mushroom. The white cup mushroom, for example, exhibits strong antioxidant capacity, particularly in terms of DPPH free radical scavenging ability. The shiitake mushroom also stands out for its high total antioxidant capacity (TAC) value among the varieties studied.
The extraction of phenolic compounds from mushrooms can be influenced by the choice of solvent, with 80% ethanol being commonly used in studies. Additionally, organically cultivated mushrooms may have higher phenolic content than traditional crops, although more research is needed in this area.
Overall, the presence of phenolic compounds in mushrooms contributes to their nutritional and medicinal value, making them a valuable component of functional foods and health products. Further studies on the phenolic profiles of different mushroom species can help maximize their potential benefits.
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Preventing mushrooms from discolouring
Mushrooms are a versatile ingredient that can be used in a variety of dishes. However, they can quickly turn slimy and discoloured if not stored properly. Here are some tips to prevent mushrooms from discolouring:
Choose the Right Storage Container
Avoid storing mushrooms in airtight containers or pre-packaged containers. Instead, transfer them to a slightly open paper bag or a small plastic container with holes poked in the lid. This allows the mushrooms to breathe and prevents moisture buildup, which can lead to mould growth and discolouration.
Keep Them Dry
Moisture is the enemy of mushrooms. When storing mushrooms, ensure they are dry and not wet. You can also line the paper bag or plastic container with a paper towel to absorb any excess moisture. This will help keep the mushrooms dry and prevent discolouration.
Store Them in the Fridge
Mushrooms should be stored in the refrigerator to prolong their freshness and prevent discolouration. Set your refrigerator temperature to 4°C or lower, and place the mushrooms on a shelf rather than in a produce drawer. This will help maintain their quality and delay discolouration.
Use Them Promptly
Even with proper storage, mushrooms have a limited shelf life. It's best to use them within a few days of purchase. If you can't use them right away, prepare them for storage as soon as you get home from the grocery store. Check the mushrooms regularly and use them as soon as you notice any signs of discolouration or slime development.
Avoid Washing Before Storage
Never wash mushrooms under running water before storing them. This can dilute their taste and negatively impact their texture. Instead, use a damp paper towel or cloth to gently wipe away any dirt or debris. Washing mushrooms before storing them can accelerate discolouration and encourage bacterial growth.
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Blue-staining mushrooms and edibility
Blue-staining mushrooms, also known as boletes, are characterised by their ability to change colour when damaged or injured. While some blue-staining mushrooms are edible, others are toxic and can cause stomach upset, pain, and even poisoning. Therefore, it is important to properly identify any blue-staining mushrooms before consuming them.
One common rule of thumb for identifying edible boletes is to avoid those with a red pore surface that bruises blue. This rule is based on the fact that many blue-bruising boletes are toxic. However, there are exceptions to this rule, as not all blue-staining boletes are poisonous. In fact, there are several edible blue-staining mushrooms that are considered choice edibles by mushroom enthusiasts.
One example of an edible blue-staining mushroom is the Cornflower Bolete, which is easily identified by its yellow colour and nearly instant blue staining when bruised. This mushroom is found in various regions around the world, including Quebec, Florida, Asia, Europe, and Australia. It is resistant to bugs and grows in sandy soil, making it a popular ingredient for chefs in Europe and Mexico.
Another edible blue-staining mushroom is the Butter Bolete, which has a short, fat, yellow stem and a pinkish to purple cap with yellow flesh that quickly turns blue. This mushroom is a bit more uncommon but can be found in hardwood forests, particularly around oaks, in Asia, Europe, Northern Africa, and North America. It is known for its firm and appealing texture, making it a popular ingredient in local markets.
Other examples of edible blue-staining mushrooms include Pulchroboletus rubricitrinus, Baorangia Bicolor, Boletellus Chryenteroides, Boletus Luridellus, and Hortiboletus Campestris. While these mushrooms are considered fair or good edibles by some, it is important to remember that edibility is subjective, and individual tolerances may vary. When trying any new mushroom for the first time, it is crucial to sample a small amount and wait a day to ensure there is no allergic reaction.
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Boletus sensibilis and oxidation
The oxidation of mushrooms refers to the process of browning or discolouration that occurs when mushrooms are exposed to air, moisture, or certain chemicals. This process is similar to the browning of sliced apples or potatoes. While all mushrooms undergo some degree of oxidation, the rate and extent of oxidation can vary depending on the mushroom's variety, freshness, and storage conditions.
In the context of "Boletus sensibilis," oxidation specifically refers to the characteristic blue staining that occurs when the mushroom is handled, bruised, or cut. This species, commonly known as the “Curry Bolete,” exhibits a marked bluing reaction due to the oxidation of certain compounds present in its flesh. The scientific name "sensibilis" is derived from the Latin word for "sensitive," reflecting this sensitivity to oxidation and the resulting colour change.
Boletus sensibilis is a species of fungus in the family Boletaceae, commonly found across North America. It was first scientifically described by American mycologist Charles Horton Peck in 1879, and its distinctive features have been the subject of discussion among mycologists. The mushroom is characterised by its vibrant appearance, with a dirty pinkish-red cap that fades to reddish cinnamon with age, and a lemon-yellow stem that can be stained pink or red.
While the blue staining of Boletus sensibilis is a notable feature, it is important to approach this species with caution. Boletus sensibilis is generally considered poisonous and non-edible by most credible mycological literature. However, there are conflicting reports, as some mycologists and mycophiles claim to have consumed these mushrooms without harm. The variability in individual specimens further complicates the identification process, as not all specimens exhibit the same characteristics, such as the curry-like odour or extensive bruising. Therefore, it is crucial to pay attention to all morphological features and exercise caution when identifying and consuming wild mushrooms.
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Frequently asked questions
Yes, mushrooms do oxidize. This is most visible in magic mushrooms, which turn blue when they are cut or bruised due to the oxidation of phenolic compounds.
The blue colour is caused by a complex mixture of linked psilocybin oxidation products.
Psilocybin is a psychotropic compound found in certain species of mushrooms. When an oxidizing laccase enzyme acts on psilocybin, it creates psilocyl radicals, which combine to form C-5 coupled subunits and then further polymerise via C-7.
Oxidation occurs when the mushroom is exposed to oxygen, which can happen when it is cut or bruised.
To prevent mushrooms from discolouring, you can try removing the gills or using only the top part of the mushroom. Alternatively, you can sauté the mushrooms separately to release their moisture before adding them to the rest of the dish.
