Monday, December 18, 2006

Where to Start? How About How Mushrooms Grow?

Where to Start? How About How Mushrooms Grow?

The first thing that most people say when the think about mushrooms is, “they’re grown in manure and kept in the dark.”

Contrary to popular belief mushrooms are not grown in manure. This is one thing that I get asked about most often. Mushrooms are in fact grown in a pasteurized substrate, which yes does contain manure, but once the whole process is finished it is not even close. Allow me to go on. This pasteurized mushroom substrate is made up of several different organic materials such as wheat, straw, hay, stable bedding, poultry litter, gypsum, corncobs, and high protein supplements such as soybean meal and feather meal. Each item does its job to create carbon and nitrogen as well as manage the pH levels of the substrate. These items mixed together create a nutritionally balanced growth medium for mushrooms.

Pasteurization of this substrate is next. This is the most important step in the making of the substrate as it eliminates any pests or micro-organisms that may be in the mixture. During pasteurization the substrate reaches a temperature of 160F/71C, all bacteria is killed. The substrate is now ready for the spawn or fungal seed to be added.

Mushrooms are “planted” using fungal mycelia instead of seeds. This “seed” or spawn is created in sterile, biosecure laboratories. Spawn making starts with a mixture of sterilized grain such as wheat, rye, or millet. Particles of mycelia are added to the sterilized grain and then incubated to promote the growth of spawn. Mushroom farmers then purchase this spawn mixture from the specialized commercial laboratories.

Mushroom spawn is then mixed thoroughly with the pasteurized substrate back at the farm. Temperature and humidity is then managed to promote the mycelial growth within the substrate. The mycelia (a mushrooms equivalent to a root) grows in all directions throughout the substrate from the spawn grain. After this spawning takes place the substrate and spawn mixture is transferred to several hundred beds or trays. A layer of casing is then spread over the mushroom bed. This casing is usually about 2 inches thick, and is made up of mostly peat moss. This casing layer acts as a water reservoir and provides a place where the mushroom mycelia form thick white rhizomorphs, which is what happens when mycelia grow together (it looks like white string). Because mushrooms need moisture, water is applied right after the casing. The beds are then watered periodically to the maximum holding capacity of the casing layer. In a few weeks the mushrooms will be ready for their first harvest.

Mushroom growers can often get more than one harvest from their single crop. Some can do two or three harvests with a 7 to 10 day break in between each harvest. The mushroom yield will decrease with each harvest of that single crop. Agaricus mushrooms are harvested for 16 to 35 days. During this harvest time bed temperatures, humidity and air ventilation are all controlled and monitored to ensure a healthy crop.

All mushrooms are hand harvested, which is very labour intensive work, believe me. After picking the mushroom from the bed the harvester then cuts off the base of the mushroom or the stump. The mushrooms are then immediately put into cold storage, this stops any mushroom deterioration or browning. This is also why you should keep your mushrooms in the fridge when you take them home. The mushrooms are then sent to packaging where they are either washed, sliced or cello wrapped in trays. Each package is weighed and then sent under a metal detector to make sure that no foreign objects were dropped into the container. They are now ready to be shipped.

The mushrooms that you see in your local grocery store were most likely picked 12-24 hours ago, so when you get them, you are getting the freshest mushrooms possible.

So there it is, the answer to every ones burning question, how mushrooms really grow. I hope this helps out all the people who have ever wondered.

Oh, and maybe I should mention that this is how whites, browns and portabella mushrooms are grown. The shiitake, enoki and oyster are really different, but we will save that story for another day.
By for now.


Anonymous said...

That was very interesting as my friend insisted they grow in 'dirty ol' manure". I also would like to know if it is imparative that mushrooms be washed prior to frying. They are washed at the packaging plant as you mentioned, so would they need it again?

Anonymous said...

If what they're grown in doesn't contain much manure, then why does it smell like a cattle ranch? I used to live a few blocks away from a commercial mushroom plant and it was AWFUL. Personally, I can never eat mushrooms after that.

Anonymous said...

All of our food grows with help from manure and decaying matter... Ever heard of the circle of life?

Anonymous said...

Helpful and interesting. Thanks!

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