Mushroom Sterilization
There are two common methods of mushroom substrate sterilization, and both work very well. The first method involves freezing the mushrooms to -20 degrees Fahrenheit. Freezing requires less energy than can be used with cold air, and since the spores don’t get clumped together during this treatment, they’re easier to remove. This method is often used to spore all types of mushrooms, whether they have a button mushroom shape or look like a curly seed.
The second method involves putting the spores into liquid nitrogen for several hours. The nitrogen attaches itself to the spores, sticking them to a sticky pad that absorbs the nitrogen gas and holds them suspended in liquid form. This method also kills off any microorganism that might be attached to the spores through chemical bonds. (In fact, many spores have been killed using this method.)
The final method is called encapsulation, and it works by putting the mushroom body into a container, then covering it with some type of spore shield. The spore shield prevents contaminants from entering the mushroom, but the container keeps the mushroom spores from coming out. Since no chemical bonds are formed when the spores are held in the shield, this method doesn’t affect the total purity of the mushroom. It also has a lower cost per mushroom than does freezing.
Mushroom Sterilization Methods Explained
All of these methods are effective, except for the last one: dry powder coating. You’ve probably seen it on some mushrooms already, as it’s the commonly used method of mushroom casing. Unfortunately, because this coating doesn’t allow for moisture to escape, it actually traps moisture within the porous surface of the mushroom, preventing any re-growth. So instead of being a cheap way to preserve mushrooms, this coating is a waste of money. Even if it were used frequently, it would be a money sink because you’d have to buy an expensive product to replace the dried powder every time you harvested a fresh mushroom.
Fortunately, mushrooms are particularly resistant to dry powder coating, allowing it to still be a useful preservation method. But even if mushrooms do dry out completely, the spores still release their spores into the air, so they’re easy to collect if you’re collecting your mushrooms for later use. It is recommended that you never use dry powder coating on mushrooms that have already been processed. The spores released during processing are very fine, and if you collect your mushrooms while they’re still wet and spongy, they will contain a lot of the mushroom material.
Dried mushroom pellets are another popular method for preservation. They’re especially good if you can get them freeze-dried right after they’re picked. These pellets can be used in any number of ways, but are most commonly used to preserve whole or sliced mushrooms that don’t come in uniform sized chunks. Another great use for pellets is to make mushroom bread, which is extremely easy and quick to do.