Can you freeze mushrooms?

Yes, but not raw and whole. Mushrooms are about 90 percent water, so a raw mushroom dropped in the freezer thaws into a soft, watery, darkened piece. The way to freeze them well is to cook out some of that water first, by blanching or sauteing, which also stops the enzymes that turn them brown. Done right, frozen mushrooms are a great shortcut for soups, sauces, and stir-fries, even if they are no longer firm enough for a raw salad.

Why raw mushrooms freeze poorly

Two things work against a raw mushroom in the freezer, and they are the same two that trouble most watery vegetables:

• High water content. At roughly 90 percent water, mushrooms form a lot of ice crystals when frozen raw. Those crystals rupture the cell walls, so the mushroom thaws limp and spongy instead of firm.
• Active enzymes. Raw mushrooms keep browning through enzyme activity, even in the freezer, dulling their color and flavor over time.

Heat solves both. Blanching or sauteing deactivates the enzymes and drives off some of the water, so the mushrooms hold their texture and color far better through the freeze. It is the same principle behind blanching potatoes before they go in the freezer.

Blanch or saute first

You have two good routes, and NCHFP describes both.

Steam blanching keeps the mushrooms closest to plain:

• Steam whole mushrooms 5 minutes, buttons or quarters 3.5 minutes, and slices 3 minutes.
• To keep them from darkening, soak them first for 5 minutes in 1 teaspoon of lemon juice (or 1.5 teaspoons of citric acid) per 1 pint (480 ml) of water.
• Cool promptly, drain, and pack with 1/2 inch (1.3 cm) of headspace.

Sauteing is the flavor-forward alternative: cook the mushrooms in a little butter or oil until they release their water and it cooks off, then cool and freeze. This is the route to take if you want them seasoned, with onion, garlic, or herbs worked in while they cook.

Either way, freeze them in flat, portioned bags with the air pressed out, and use them within several months for the best quality.

Storing fresh mushrooms before they get there

If you are not freezing them yet, fresh mushrooms last longest kept dry and breathing:

• Paper, not plastic. Store mushrooms in a paper bag, which absorbs excess moisture and lets them breathe. Sealed plastic traps humidity and turns them slimy fast.
• Shelf, not crisper. Keep them on a main fridge shelf rather than the high-humidity crisper drawer, which speeds spoilage for mushrooms.
• Do not wash until you cook. Mushrooms soak up water, so rinsing them early shortens their life. Brush off dirt or wipe with a damp cloth at cooking time.

Stored this way, whole mushrooms keep about 7 to 10 days and sliced ones 4 to 7. Sturdier varieties like portobello and shiitake tend to hold a little longer than delicate white buttons, but the storage method matters more than the type. When they start to wrinkle, darken, or feel tacky, that is the time to cook and freeze them rather than let them go.

How to freeze mushrooms

1. 1

   Clean and cut to size

   Wipe mushrooms clean (do not soak them). Leave small ones whole, slice or quarter larger ones so they blanch and freeze evenly.

2. 2

   Blanch or saute

   Steam-blanch by size (whole 5 minutes, buttons 3.5, slices 3), or saute in butter or oil until the released water cooks off.

3. 3

   Treat against darkening (if blanching)

   Soak first for 5 minutes in 1 teaspoon lemon juice per 1 pint (480 ml) water to keep the color bright.

4. 4

   Cool, drain, and pack with headspace

   Cool promptly, drain well, and pack into bags or containers leaving 1/2 inch (1.3 cm) of space. Press the air out of bags.

5. 5

   Label, freeze flat, use within months

   Date the bags, freeze them flat to stack, and use within several months. Cook straight from frozen.

What goes wrong

• Freezing them raw and whole. They thaw watery and dark. Blanch or saute first, every time.
• Washing before storing or freezing. Mushrooms drink up water, which speeds sliming in the fridge and worsens the texture in the freezer. Clean them at cooking time.
• Sealing fresh ones in plastic. Trapped moisture turns them slimy. A paper bag on a shelf keeps them firm longer.
• Thawing before cooking. Thawed mushrooms turn to mush. Drop them into the pan straight from the freezer.
• Expecting raw-salad texture. Frozen mushrooms soften no matter how you prep them. Plan to use them cooked.

The short version

You can freeze mushrooms, but not raw and whole, because at about 90 percent water they freeze into a soft, dark sponge. Blanch them (steam whole 5 minutes, slices 3) or saute them first to stop the enzymes and cook off the water, then freeze flat in portions for several months. Before that, keep fresh mushrooms in a paper bag on a fridge shelf, unwashed, for 7 to 10 days. Either way, plan to use them cooked, where their softer texture does not matter at all.