Mushroom Market Summary
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Mushroom Industry Overview
While considered fresh produce, mushrooms are neither fruit nor vegetable, but fungus. Unlike most produce, mushroom growth is actually hampered by sunlight. Instead, mushrooms feed on decaying organic matter and thrive in the dark. Cultivated for centuries in China, there are more than 38,000 varieties of mushrooms (some highly toxic), with only about 300 edible species. The edible portion of a mushroom is the toadstool, which includes the stem and the cap. The wheel spoke-like underside of the cap contains the gills, which hold spores for reproduction.Types & Varieties of Mushrooms
Popular edible mushroom varieties include button, portabella, oyster, enoki, shiitake, crimini, lobster, porcini, and morels. Button mushrooms (Agaricus bisporus) are the most commonly grown in the United States. These are usually classified according to color: whites, creams, and browns. Few varieties are grown domestically due to the difficulty of cultivation. Pennsylvania leads the nation, producing two-thirds of U.S. production. Morels, oysters, and chanterelles are often gathered in the wild, especially in the northeast and Pacific Northwest of the United States. Matsuke, white truffles, and black truffles are exclusively gathered from the wild as they need to interact with animals and trees in their natural environment to thrive.
The Cultivation of Mushrooms
Although cultivating mushrooms is complicated and labor intensive, crop lifecycles are a relatively brief 6 to 7 weeks (depending upon variety) and yields can be very high. Commercial mushrooms are cultivated indoors in two stages: Stage 1 involves preparing the mushrooms’ food (nutrient-rich compost) and Stage 2 is the actual growing and harvesting of the mushrooms themselves. In Stage 1, natural or synthetic compost is prepared (natural uses straw, hay, and manure) while synthetic can be made of corncobs, cottonseed hulls, corn stalks, dried grains, or cocoa bean hulls without manure. Both kinds require the addition of nitrogen-rich supplements and moisture. Once the odor of ammonia disappears and the compost appears dark-brown, Stage 1 is complete. Heat is then used to pasteurize the material, killing off harmful microbes and insects. Mushrooms thrive in cool, moist, well-ventilated environments. For Stage 2, compost is usually moved to slabs in a growing room. Shiitake mushrooms grow on logs in the wild, but are cultivated commercially on synthetic logs made from sawdust, straw, corncobs, and other materials. Temperatures must remain cool during cultivation, ranging from 50 to 75°F. Humidity should remain above 70% to prevent drying and splitting. Growers spread mushroom spawn over the compost, then after 14 to 21 days soil is spread over the beds in a process known as casing. Beds must be watered regularly for about 3 to 4 weeks until the first mushrooms appear.
Pests & Diseases Affecting Mushrooms
With indoor growing the norm and pasteurization of the growing environment, pests are not a significant problem though various flies, gnats, mites, and millipedes, as well as nematodes will affect the growing process. More common is postharvest damage from rough handling (causing bruises and discoloration) or improper cooling (leading to blackened stipes and gills and curled caps). Although mushrooms are a form of fungus, they are still susceptible to a range of fungal, bacterial, and viral diseases including various mold, mildew, spot, and blotch outbreaks. Blotch and other bacterial diseases can lead to spoilage if not eliminated during growth and harvest.Storage & Packaging of Mushrooms
Mushrooms should be cooled to between 32 and 39°F. Properly cooled and packaged mushrooms can be stored for 7 to 9 days at between 32 to 34°F with 95% relative humidity. Even a small rise in storage temperature to 36°F shortens storage life by several days. References: PennState Extension, UC Davis Postharvest Technology Center, University of Florida/IFAS Extension, University of Idaho, USDA, Western Growers Association.Grades & Good Arrival of Mushrooms
Grades consist of U.S. No. 1 and U.S. No. 2; quality defects include maturity, shape, stem length, diameter, open veils, and trim. Condition defects include firmness, discoloration, spots and decay, and exposed gills. Sizes run from small (three-quarters to 1.25 inches) to jumbo (3 or more inches).Generally speaking, the percentage of defects shown on a timely government inspection certificate should not exceed the percentage of allowable defects, provided: (1) transportation conditions were normal; (2) the USDSA or CFIA inspection was timely; and (3) the entire lot was inspected.
| U.S. Grade Standards | Days Since Shipment | % of Defects Allowed | Optimum Transit Temp. (°F) |
| 5-1 | 5 4 3 2 1 | 8-2 8-2 7-2 6-1 5-1 | 32° |
