How to Preserve Mushrooms

Pennsylvania is a major producer of mushrooms. According to the Mushroom Council, the mild-flavored, white button mushroom comprises 90% of the mushrooms consumed in the United States. Light tan to rich brown, capped crimini mushrooms (also known as baby bellas) have a deeper, earthier flavor than the white button mushrooms.

Fresh mushrooms stored in their original packaging or in a porous paper bag will keep for up to one week in a refrigerator. Mushrooms are low in calories and fat, and are a good source of B-complex vitamins, antioxidants and minerals.

Mushrooms may be canned, frozen, dried or marinated as a pickle.

Select brightly colored, small to medium-size mushrooms. Do not preserve wild mushrooms; the toxins of poisonous varieties of mushrooms are not destroyed by drying or cooking. Only an expert can differentiate between poisonous and edible varieties.

Directions for freezing mushrooms are as follows. Choose fresh mushrooms and sort according to size. Wash thoroughly in cold water; do not soak them. Trim off ends of stems. If mushrooms are larger than 1-inch across, slice them or cut into quarters. Mushrooms should be cooked before freezing; either steam or heat them in fat to stop enzyme reactions. Steamed mushrooms will keep longer than those heated in fat, but sautéed mushrooms have more flavor. Tray freezing before packaging is desirable.

To steam mushrooms, pretreat them by dipping mushrooms in a solution containing 1 teaspoon lemon juice or 1-1/2 teaspoons citric acid to a pint of water. This helps to preserve their color. Then steam whole mushrooms 5 minutes; buttons or quarters, 3-1/2 minutes, and slices, 3 minutes. Cool promptly, drain and package, leaving 1/2-inch headspace. Seal and freeze.

An alternative method of freezing mushrooms is to heat small quantities of mushrooms in butter, margarine, or olive oil in an open fry pan until almost tender. Cool in air or set pan in which mushrooms were cooked into cold water. Pack into containers, leaving 1/2-inch headspace. Seal and freeze.

For canning and pickling, mushrooms should have short stems, tight veils (unopened caps) and no discoloration. Because mushrooms are a low-acid food, care must to taken to control the growth of spoilage organisms — especially Clostridium botulinum. Mushrooms that are not pickled must be processed in a pressure canner.

Directions for canning mushrooms are as follows. Trim stems. Soak in cold water 10 minutes to remove dirt. Wash in clean water. Leave small ones whole; cut larger ones. Cover with water in a saucepan and boil 5 minutes. Pack hot into hot half-pint or pint jars, leaving 1-inch headspace. One-fourth teaspoon salt may be added to half-pint jars or 1/2 teaspoon salt to pint jars if desired. For better color, add 1/8 teaspoon (375 milligrams) ascorbic acid per pint. Fill jars to 1 inch from top with boiling water. Remove air bubbles. Wipe jar rims. Adjust lids and process for 45 minutes in a dial-gauge pressure canner at 11 pounds pressure or in a weighted-gauge pressure canner at 10 pounds pressure. Make the following adjustments for higher altitudes: In a dial-gauge canner at altitudes of 2,001 to 4,000 feet, process at 12 pounds pressure; between 4,001 and 6,000 feet, process at 13 pounds pressure; over 6,000 feet, process at 14 pounds pressure. In a weighted-gauge pressure canner at altitudes above 1,000 feet, process at 15 pounds pressure.

Pickled mushrooms must have adequate amounts of vinegar and/or bottled lemon juice to control the growth of Clostridium botulinum. It is very tricky to use oil in canning recipes, because oil can surround C. botulinum spores, allowing them to produce the botulism toxin that can cause serious illness. A recipe for canning marinated whole mushrooms can be found on the National Center for Home Food Preservation website.

Dried mushrooms are convenient for use on camping trips and can easily be rehydrated in soups, sauces and casseroles. (Think skillet casseroles if you are camping.) Directions for drying mushrooms: Scrub mushrooms thoroughly. Discard any tough, woody stalks. Cut tender stalks into short sections. Do not peel small mushrooms. Peel large mushrooms and cut into 1/4-inch slices. It is not necessary to blanch mushrooms for drying. Place in a dehydrator at 125 F and dry until brittle. This may take 8 to 10 hours. When mushrooms are cool, store in an airtight container or bag. Dried mushrooms will absorb moisture from the air and become limp and spoil if not in a totally vapor-proof container.

If you have food preservation questions, a home economist is available to answer questions on Wednesdays from 10 a.m. to 2 p.m., by calling 717-394-6851 or writing Penn State Extension, Lancaster County, 1383 Arcadia Road, Room 140, Lancaster, PA 17601.

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