Drying Mushrooms

Drying is the oldest way to keep a mushroom harvest and often the most flavourful. Removing about 90% of the water concentrates everything left, and dried shiitake carries roughly fifteen times the glutamate of fresh by weight. This is Colorado State University Extension’s tested method, with the one point where foragers usually disagree with it.

⚠ Drying does nothing to a poisonous mushroom. CSU: “The toxins of poisonous varieties of mushrooms are not destroyed by drying or by cooking.” Identification comes first.

A reference card: the tested extension procedure.

Ingredients

Fresh mushrooms

1 teaspoon citric acid per quart of water

Directions

Key ingredients

Citric Acid

Prepare. Scrub. Discard tough, woody stalks. Slice tender stalks 1/4 inch thick. Peel large mushrooms and slice them. Leave small mushrooms whole.
Dip. Soak 10 minutes in the citric acid solution. Drain.
Dry. Use a dehydrator at 140 °F, or an oven preheated to 140 to 150 °F with the door propped open. Drying takes 8 to 12 hours.
Test. CSU’s test is dry and leathery.
Store. Store airtight in a cool, dark place.
To use. Soak in hot water (15 to 30 minutes), lift the mushrooms out, and pour the soaking liquid off its grit. Use the liquid too, since it is full of flavour. For dried shiitake, soak cold (see Shiitake Dashi 干し椎茸の戻し汁).

Notes

Where this came from Colorado State University Extension, fact sheet 9.308, “Drying Vegetables”. The NCHFP notes that dehydrators are designed to dry foods “fast at 140ºF”.

Where the sources disagree Many foragers’ guides skip the citric-acid dip, wipe rather than scrub, and dry until brittle and crisp rather than leathery. Crisp pieces store longer and grind easily to powder. CSU’s leathery endpoint is the tested one. For long storage, drier is the safer choice.