Preservation by Dehyrdating
Drying is the oldest and most widespread way to preserve mushrooms. Long before refrigeration, it was how mushrooms traveled from forest and farm to market. Fresh mushrooms are heavy with water, fragile, and quick to spoil; drying solves all three problems at once, cutting weight, halting spoilage, and making months of storage possible without ice, fuel, or specialized containers.
It also changes the food. Many Asian culinary traditions came to prefer dried mushrooms over fresh, not as a substitute but on their own merits. Drying concentrates aroma and deepens umami, particularly in shiitake, and the soaking liquid released during rehydration becomes an ingredient in its own right — the base of soups, sauces, and braises.
1. Prepare the mushrooms
Trim off any misshapen, irregular, or insect-damaged areas. De-stem what you plan to dry; stems can be dried separately, saved for stock, or powdered into a seasoning.
The best drying happens within 2–3 days of picking. Not only is there less chance of contamination, but a freshly dried shiitake takes on a bright yellow color, while one that has sat in the fridge for a week often turns dull brown. Rain-soaked mushrooms should be dried immediately.
Sort by size, since smaller mushrooms finish well before larger ones. Some growers leave mushrooms whole and others slice them. Slicing introduces more tools and more opportunities for contamination, so sanitation becomes more critical if you go that route.
2. Consider starting in the sun
Place whole mushrooms gills up on food-grade trays. Organizing them gills up preserves the flavor. We recommend placing the mushrooms directly on the trays of your dehydrator so the mushrooms can move from sun to machine without being handled again.
Cover the trays with screening to protect them from insects and critters, and set them in sunlight for at least 5 hours, ideally longer. Some growers build solar drying structures to raise the temperature and speed things up. These work well as long as the container protects mushrooms from insects and other contaminants, and uses glass or a plastic that doesn’t block UV rays.
Why UV matters: exposure to ultraviolet light converts ergosterol in mushroom cell walls into vitamin D₂, sometimes reaching levels comparable to or exceeding common dietary sources. Even brief exposure to direct sunlight before or during drying can meaningfully increase nutritional value. It is a rare case where post-harvest handling directly improves a measurable nutrient.
3. Finish in a dehydrator
Food dehydrators are the most reliable option, ideally operating between 110–130°F (43–54°C). Temperatures up to 180°F (82°C) still preserve most structural and medicinal compounds, though some volatile aromatics decline. Drying time depends on how much the solar stage dried the mushrooms.
Convection ovens can work, but they are less consistent and more energy-intensive. Passive drying with fans can be effective for tougher species such as reishi or cordyceps, particularly in low-humidity environments.
Watch for case-hardening, where the exterior dries quickly and traps moisture inside. Thin slicing or shredding increases surface area and speeds up the drying process. Avoid purées and pastes as they dry unevenly and poorly.
4. Know when they’re done
Finished mushrooms are leather hard: not soft in any place, but not overly brittle either. This is learned by feel over time, and you can verify it by weighing the mushrooms fresh and then dried. As a general rule, expect roughly 1–2 oz of dried product per pound (16 oz) of fresh mushrooms, or the dry weight being 15 - 20% of the fresh weight.
5. Package and store
Airtight is the rule: a locking plastic bag or a glass jar both work well. Store out of direct light. Properly dried and packaged, mushrooms should hold their quality for at least 6–12 months.
6. Make powder (optional)
Grind fully dried stems or caps in a blender or coffee grinder dedicated solely to this purpose, then package in glass or plastic spice jars. Grind in low humidity (ideally below 50%) to prevent clumping, and sift the result for uniformity. Powder is the base for seasoning blends, usually mixed with salt and herbs or garlic for a ready-to-use production