The mushroom is just one of a very large, diverse group of organisms called fungi. It is similar to a plant but lacks chlorophyll, so it cannot produce its own food through photosynthesis. The mushroom is a decomposer that absorbs nutrients from materials such as compost, leaves, decaying wood, and soil. There are many types of mushrooms, varying in size, shape and color, with surfaces that range from smooth and silky to pitted and honeycombed. The most common and readily available is the cultivated white mushrooms, which have a mild flavor and can be used in many types of dishes. Wild mushrooms, such as chanterelle, morel, shiitake, portobello and oyster, will provide a more intense and exotic flavor. Generally mushrooms contain 90 percent water and have few calories. The fat and carbohydrate content is minimal and they do not contain any cholesterol. They are rich in protein and contain vitamins such as B, C and D, and a few contain vitamin A. Be aware that some of the vitamin values are destroyed during the cooking process. When selecting, choose mushrooms that are firm, fresh and free of blemishes. Check underneath their caps for tightly closed brown gills and be sure the surface of the cap is not dried and woody on the edges. Also look for slimy or sticky surfaces and for any coloring that is not normal.
When cleaning mushrooms, avoid using water, which reduces the flavor of the mushroom and is absorbed into the mushroom only to be released into foods combined with them. Water will also have a tendency to turn mushrooms grey in color. Therefore, use a brush or a damp paper towel to clean sand, grit and other debris from the pits and ridges. If you must use water, use as little as possible and dry quickly with a paper towel. Cut lengthwise and check interior for insects and other debris.
If storing in the refrigerator, do not clean the mushrooms before storing. Store uncleaned mushrooms in a paper bag or their original container allowing them to breathe. Storing in plastic or airtight plastic containers causes mushrooms to retain moisture and decay faster. Mushrooms stored at temperatures between 34ºF and 38ºF with humidity levels around 85% to 90% will keep them in ranges that are considered best for storage. To preserve mushrooms for an extended period of time, use other methods such as freezing, drying, salting, canning, or pickling.