How Are Mushrooms Grown Commercially?

Most people like mushrooms and there are many ways you can eat them. They can be fried, baked, grilled, and so on. Some people grow their own mushrooms, but most people just buy them in the store. So, how are mushrooms grown commercially?

Mushrooms are commercially grown on mushroom farms, in dark buildings. The process of growing mushrooms consists of 6 steps, which are composting, finishing the compost, spawning, casing, and cropping.

Mushrooms are very healthy, and a great source of many nutrients. One serving of mushrooms can give you a lot of vitamin D, potassium, and selenium. That being said, there are some environmental concerns when it comes to the mass production of mushrooms. Many believe that it’s not sustainable due to the fact that most phases of growing mushrooms are run by different businesses. Mushrooms travel thousands of miles to reach their next stage of growth. Once they finally reach stores, they mostly aren’t fresh anymore. Another big concern is the smell that is emitted during the production of the compost. The compost is produced near the residential area and the violent smell bothers the residents. 

How are mushrooms grown commercially?

Mushrooms are very healthy. They are a good source of many nutrients. For example, recent research has found that when UV light is shined on mushrooms, there is a major boost in the vitamin D2 content of the mushrooms. A single serving of those mushrooms will contain over 800% of the recommended daily allowance of vitamin D2. They only have to be exposed once for five minutes after being harvested. That makes mushrooms great food for people who don’t eat fish or drink milk.

Mushrooms contain a lot of complex carbohydrates, such as glucans and glycogen, monosaccharides, disaccharides, sugar alcohols, and chitin. These polysaccharides are structural components of the cell walls and are considered to be dietary fiber. Eating enough dietary fiber helps prevent many diseases prevalent in affluent societies. 

Crimini mushrooms are a great source of potassium, which is very important for the regulation of blood pressure, maintenance of water in fat and muscle, and ensuring the proper functioning of cells. One 3-ounce Portobello mushroom contains more potassium than a banana. 

Portobello and crimini mushrooms are a great source of antioxidants. They rank with carrots, green beans, red peppers, and broccoli as good sources of dietary antioxidants. These mushrooms are a good source of polyphenols, the primary antioxidants in vegetables, and they are the best source of L-ergothioneine, which is a potent antioxidant only produced in nature by fungi. 

One serving of Crimini mushrooms will provide you a bit less than ⅓ of the RDA for selenium. Selenium can decrease prostate cancer by more than 60%. 

Commercial mushroom farming consists of 6 steps:

1. Composting

The first step is composting. This is done by mixing and wetting the ingredients and stacking them in a rectangular pile with tight sides and a loose center. These ingredients are sprayed with water, nitrogen supplements, and gypsum.

The reason why gypsum is added is to minimize the greasiness compost normally tends to have. It increases the flocculation of certain chemicals in the compost, and they stick to straw or hay instead of filling the pores between the straws. This lets air penetrate the pile more easily, and the air is essential to the composting process.  

The compost should be turned and watered about every 2-3 days. Turning the compost will let you relocate the straw or hay from a cooler to a warmer area in the pile, and add supplements. It is very important that you add the right amount of water because too much will exclude oxygen by occupying the pore space, and too little can limit the growth of bacteria and fungi. Usually, water is added up to the point of leaching when the pile is formed and at the time of first turning. 

The compost will become a food source most suited for the growth of the mushroom. The process will stop if there isn’t adequate moisture, oxygen, nitrogen, and carbohydrates present throughout it.  

The first phase lasts 6 to 14 days, depending on the material. 

2. Finishing the compost

The second step is finishing the compost. Pasteurization is a very important part of this process because it kills any insects, nematodes, pest fungi, or other pests that could be present in the compost. It also removes ammonia that formed during composting. 

Finishing the compost is done in 3 ways, depending on the type of production system used. If the mushrooms will be produced with a zoned system of growing, compost is packed into wooden trays, and these trays are stacked six high and are moved into an environmentally controlled room for finishing the compost. After that, the trays are moved to special rooms, which are designed to provide the optimum environment for each step of the mushroom growing process.

If the mushrooms will be grown using a bed or shelf system, the compost is placed directly in the beds, which are in the room used for all steps of the crop culture. 

The process of finishing the compost is a controlled, temperature-dependent, ecological process that uses air to maintain the compost in a temperature range which is best suited for microorganisms to grow and reproduce. 

When this process is done, the compost temperature has to be lowered to about 75° to 80°F before spawning begins. The moisture content should be between 68% and 72%, and nitrogen levels should be 2.0% to 2.4%. 

3. Spawning

The third step in the production of mushrooms is spawning. Mushrooms produce millions of microscopic spores on mushroom gills lining the underside of a mushroom cap as they mature. The spores work similarly to the seeds of a plant. That being said, growers don’t use mushroom spores to ‘seed’ mushroom compost because they germinate unpredictably and that makes them unreliable. They use mycelium which can be propagated vegetatively from germinated spores. 

The spawn-making process is started by sterilizing a mixture of millet grain plus water and chalk. Then the mycelium is added to sterilized grain and shook 3 times at 4-day intervals over a 14-day period of active mycelial growth. When the grain is colonized by the mycelium, the product is called spawn. It can be refrigerated for a few months. 

Spawn is then distributed on the compost and mixed in. How long it will take spawn to colonize the compost depends on the spawning rate and its distribution, the compost moisture and temperature, and compost supplementation. Usually, it takes about 13 to 20 days.

4. Casing

Once spawning is done, it’s time for the casing.

The casing is a top-dressing that is applied to the spawn-run compost on which the mushrooms eventually form. It is usually made out of a mixture of peat moss with ground limestone. The most important things casing does are supplying water to the mycelium for growth and development, protecting the compost from drying, providing support for the developing mushrooms, and resisting structural breakdown following repeated watering. 

The most commonly used material for the casing is sphagnum peat moss, which can range from brown to black. 

Once the casing is done, the compost temperature has to be around 75°F for up to 5 days after the casing, and the humidity has to be high. 

5. Pinning

The next step after casing is pinning. 

Mushroom initials develop in the casing. When n initial quadruples in size, the structure is a pin. These pins keep expanding and growing larger through the button stage, and ultimately a button grows to a mushroom. Mushrooms are ready for harvesting after 18 to 21 days after casing.

In order for pins to appear, the carbon dioxide content of room air is lowered to 0.08 percent or lower, depending on the cultivar, by introducing fresh air into the growing room. It is very important when fresh air is introduced. It is usually best to ventilate as little as possible until the mycelium has begun to show at the surface of the casing. 

6. Cropping

Cropping is the last step of producing mushrooms. 

The cropping cycle lasts about 7 to 10 days. To get good results, air temperature during cropping should be held between 57° to 62°F. This temperature is good for mushroom growth but also kills pathogens and insect pests. The humidity should be high enough to minimize the drying of the casing but not high enough to cause the cap surfaces of developing mushrooms to be clammy or sticky.

The harvesting cycle may take longer or shorter depending on the temperature, humidity, cultivar, and the stage when they are picked. Once the mature mushrooms are picked, an inhibitor to mushroom development is removed and the next flush starts to mature. Mushrooms are mostly picked when the veil is not too far extended because consumers want closed, tight, and white or brown mushrooms. 

One most common environmental concern is the smell of the mushroom factories. Mushroom compost preparation is usually very close to residential areas, which causes a lot of nuisance complaints, mostly because of the odor that is emitted while preparing compost. 

Where are mushrooms grown commercially?

Mushrooms are mostly grown in China. About half of all mushrooms grown commercially are grown there. China is followed by the USA and the Netherlands. Spain, France, and Poland are among medium producers of mushrooms, while Italy, Canada, Ireland, and the UK produce the least amount of mushrooms. 

Many people don’t know this, but one small region of the USA produces almost half of the USA mushrooms. 

Chester County has sixty-one mushroom farms that grow over 400 million pounds of mushrooms worth $365 million. Mushroom farming is the leading agricultural pursuit in Chester County, which is the largest producer of fresh mushrooms in the whole United States. Its 61 mushroom farms produce 47% of total produced mushrooms in the USA. The contribution to the economy is around $2.7 billion. The industry has 

10,000 employees, who are mostly Hispanic. 

The surrounding landscape is full of single-level cinderblock buildings where mushrooms are grown. Most mushrooms that are produced in this area belong to the Agaricus family. They have become very popular as a substitute for grilled-steak. Some other types of mushrooms grown in this region are shiitakes, oysters, maitakes, beeches, enokis, and pom-poms.

Are commercial mushrooms grown in manure?

Mushrooms are grown in mushroom farms, in dark buildings. They can either be grown in manure, or in wood chips. 

There is no way to tell if mushrooms have been cultivated in manure or wood chips just by looking at them. Organic mushrooms can also be grown either in manure or in wood chips. The only way you can know what mushrooms have grown in is if it says on the label. 

Buying organically grown mushrooms could put your mind somewhat at ease because the National Organics Program has some very important restrictions on the use of compost in the production of all certified organic foods. It stated that raw animal manure cannot be used less than 120 days before harvest if a food, in this case, mushrooms, has an edible part that comes into contact with the soil. These restrictions help prevent food from being contaminated with bacteria like E. coli.

But what if you don’t want to buy organic mushrooms, are they still safe if they have been grown in manure?

Research showed that heat generated during normal composting kills human pathogens in manure needed to grow mushrooms. This means that there will be no restrictions on the mushroom industry composting process. All composting treatments that say they reduce levels of human pathogens have to be a scientifically valid, controlled, physical or chemical process or composting process. They have to meet or exceed specific microbial standards. This means that even if mushrooms have been grown in manure, they are still safe and they won’t cause you any problems if you eat them. 

How do you grow mushrooms on a large scale?

The process of growing mushrooms on a large scale is split into a few different phases. These phases are often run by separate businesses hundreds or even thousands of miles apart.

The first phase in producing mushrooms on a large scale is done by a spawn producer. This is a specialized laboratory-based operation. During this phase, pure mushroom cultures are multiplied up and expanded to grow on tonnes of grain.

The second phase is done by a substrate producer. This phase involves preparation and inoculation of the bulk growing substrate, from which the mushrooms will eventually grow from.

The third phase is done by a mushroom producer. Large mushroom farms mostly only do the fruiting stage and buy in the ready to fruit substrate from others. These substrates often have to travel thousands of miles to reach the farm.

The fourth and last phase is done by a wholesaler or retail food outlets. The mushrooms travel by plane or truck to a huge warehouse. From there, they will go to regional distribution hubs before finally being transported to end up in shops or restaurants.

This process has some flaws. Raw material usually travels a long way to the substrate production facility. They are hydrated and then pasteurized or sterilized using heat in production facilities. This hydrated substrate also often travels thousands of miles to the farm for the mushrooms to grow. The workers on these mushroom farms are often underpaid for their hard labor. Once these mushrooms finally reach consumers they aren’t really fresh anymore. Growing mushrooms on a large scale don’t seem very sustainable.