You can preserve mushrooms by drying, freezing, salting, powdering or pickling them. Regardless of the preservation method, always preserve mushrooms that are fresh, clean and in good condition.
If using a dehydrator to dry the mushrooms, place mushroom slices on the racks, and follow the manufacturer's instructions. If using an oven, place the mushroom slices on a cookie sheet lined with parchment paper, and set the temperature to 150 degrees Fahrenheit. You may also thread the slices with a needle and thread in order to hang them up to dry.
To preserve mushrooms by salting, use a ratio of three parts salt to one part mushroom. Slice the mushrooms thick, and pour a layer of salt into a glass jar. Add a layer of mushrooms, and pour another layer of salt. Add layers until the jar is full before closing it.
Some mushrooms may be frozen raw, while others have to be sautéd first. To freeze them raw, slice them and place them in a single layer on a cookie sheet before putting them in the freezer. Remove them after two hours, and put them in freezer containers before returning them to the freezer. You may sauté mushrooms in butter or oil to remove the moisture. Allow them to cool before placing them in storage containers for freezing.
To powder mushrooms, dry them before placing them in a coffee grinder to grind them into powder. Pickling involves placing the mushrooms in pickling brine to preserve them.