Preserving Harvested Mushrooms
by John Rahart
Mushroom gathering in New Mexico, especially collecting for the pot, is often sparse, but punctuated with episodes of abundance. Especially during these avalanches of abundance, preserving the harvest and preventing waste can be demanding to be sure. People often ask me what I do when I collect at such times. Though I touched upon this previously in a Newsletter, people continue to press me for a more comprehensive dissertation. So here goes.
1. Blanching and Freezing - This remains my most versatile method of preserving large quantities of mushrooms, especially those requiring rapid or delicate handling, such as Coprinus comatus (Shaggy Mane). Also, washing in water does not hurt the end product, so mushrooms noted for trapping sand and dirt can be thoroughly washed first.

Method - Washed Mushrooms are taken directly from a cold water wash basin or sink where they have been cleaned, washed and are still soaking in the tub of water with a colander or sieve, drained for a moment and plunged directly into a pot of boiling water for 1 to 2 minutes after water re-boils. They are then removed with a sieve or colander and are plunged into old water to stop the cooking process. Once cool, the mushrooms are drained of rinse water and placed in plastic freezer containers. A mass-production line can be set up. blanched product into cold water, while cooling, new raw product into hot blanch liquid, etc. The process becomes very efficient.

At the end I cool the blanching water and place into the containers of mushrooms, leaving enough headspace so freezing won't overfill or rupture the containers (usually 1 to 1½ inches is fine for most freezer container shapes. I especially prefer small 8 oz yogurt containers; they are a perfect size to drop into a pot of soup. (½ to ¾" headspace is OK for these.)

Uses - I use these frozen mushrooms in soups and stews throughout the non-collecting months by simply dropping the entire frozen contents into soup 20 minutes to ½ hour prior to the soup completion time, letting it simmer the last 20-30 minutes and AH! Perfection. Makes especially good Beef Barley soup with shaggy manes.

Advantages - Blanching stops enzymatic action and prevents mushrooms from turning into mush. Washing gets rid of sand and dirt with no adverse effect in the end product. Texture for soup remains good. Very easy to do large amounts of mushrooms in a relatively short time. Very convenient to use, just plop frozen mass directly into soup cooking. Pre-thawing is not necessary or desirable. Flavor preservation is exceptional.

Disadvantages - Not as high quality a product for uses requiring frying, sautéing, or crisping of mushrooms, but actually can still be done.
2. Steaming - Very similar to blanching in liquid, except steam instead of liquid is used to blanch.

Method - A steamer basket is placed in a boiling water bath such that it remains above the level of the boiling liquid. Mushrooms are steam blanched 2 minutes or so. The mushrooms are then cooled either in a cold water bath and then drained and packed in freezer containers, or the mushrooms are spread directly from the steamer basket onto a cookie sheet sprayed with Pam or vegetable non-stick, spread into a single layer and then frozen on the cookie sheet until fully frozen. They can then be freed from the cookie sheet and placed into freezer bags as individually free mushroom pieces. These can be used in soups, stews, etc., or can be placed frozen directly into an ongoing stir-fry for great results. Do not thaw first. Place a few at a time into cooking stir-fry and keep the temperature up.

Uses - Soups and stews for frozen water soaked container mushrooms or stir-fries and sautéed dishes direct from the bag for free-frozen pieces; also tempura or batter fried used frozen from the bag, batter dipped still frozen and fried immediately - AH! Wonderful.

Advantages - Convenient, more versatility than water blanching. Excellent taste and texture preservation.

Disadvantages - Somewhat more time-consuming and more complicated than water blanch. Also, does not clean dirt, sand, and grit as well as water blanching, so pre-selecting the cleanest mushrooms works best for this method.
3. Oil or Butter Sautéing - then Freezing - My favorite method of preserving Agaricus genus mushrooms, especially those with anise or almond overtones, Boletes, Chanterelles, any of the drier textures mushrooms such as Lobster mushrooms, and Man on Horseback (Tricholoma flavovirens) benefit from the sauté oils and do this method justice.

Method - Slice, chop, or prepare mushroom shape/pieces as preferred. Fry in butter or olive or walnut oil for ant standard fried mushroom dish, stopping the cooking process slightly before normal and allow to cool by transferring mushrooms to cool pie plates, glass or baking dishes, etc. When cool, portion mushrooms into small freezer containers and freeze. To use, simply pop out the portion onto a sauté pan with a little of the same oil or butter used to first prepare them. Do Not pre-thaw.

Advantages - Best reproduces the texture and taste of a mushroom sauté. Easy and convenient.

Disadvantages - Usually more air exposure inside freezer container; and air is what causes freezer burn, so may not preserve the quality for as long in the freezer as those methods excluding air better such as freezing under broth. Patting mushrooms gently to bottom of container into solid block and then placing some plastic wrap directly on mushrooms before covering with container lid helps some.
4. Drying - The age old method of drying mushrooms is still one of the best methods of preserving mushrooms. Boletus edulis are seen all over Italy, dried and wrapped in often elaborate (and expensive) displays. Methods vary from good old sun/air drying to machine drying (dehydrators) to oven drying. Different methods give somewhat different results, but it is mostly a question of how elaborate and how much are you willing to invest to accomplish this. Many good home use dehydrators are on the market. Units with Temperature control, such as the top of the line American Harvester, are particularly versatile, especially in humid areas or during spells of rain.

Method - Slice/prepare mushrooms, set on drying trays or rack and sun dry (protect from insects and flies) or place in dehydrator or oven (very low temperature 100ºF to 150ºF) - Dry to low moisture level, place in air tight bags or jars and store. To re-constitute cover with warm or hot water 15 minutes to several hours (varies with species) until plumped up. Do not use only the water from the tap for your recipes; be sure to use the soak water from the mushrooms as it is richly flavored. Save it for other later uses if the recipe does not call for liquid. Freeze it if no immediate us is at hand. It's worth it. David Arora mentions that the pore-masses from Boletes can be dried separately from the mushrooms, soaked to reconstitute not for the pore-masses, as they are slimy, but for the soak liquid reserved after wringing out the masses for uses in gravies, soups, etc. It is truly a wonderful use of something otherwise usually discarded.

Advantages - Drying preserves mushrooms for very long periods of time with little or no deterioration in flavor or quality. Drying actually intensifies the mushroom flavor of many species, especially the Boletes. Convenient and easy to store and use, requiring no special equipment or refrigeration.

Disadvantages - Drying often toughens or changes mushroom texture; many will not fry or sauté after being dried. Sometimes flavor changes character after drying occurs. Volatile flavors and aromas are often lost. Re-constituting does not necessarily restore good texture in many cases. Equipment can be elaborate and expensive.
5. Canning - Since mushrooms have insufficient acid, they are susceptible to Clostridium botulinum (botulin) contamination and require pressure canning to be safely canned. Refer to a reliable canning guide and follow manufacturers specifications and instructions exactly.

Advantages - Versatility of product. If properly done, anything can be canned, so stews, soups, preparations containing mushrooms can be prepared, then canned.

Disadvantages - Expensive, sometimes finicky equipment is necessary, complicated processes and preparation possible and very strict adherence to methods, procedures, And techniques is an absolute must. This is not a method to where one can cut corners.
6. Pickling - Pickling is an acid treatment and preservation process for foods, usually either lactic acid produced by brine or vinegar added directly to the items preserved. Follow only proven recipes and techniques from reputable guides. Extension services and pickling and canning books are good sources. Agaricus, especially the somewhat bland store bought varieties, Shiitakes, Oyster mushrooms, and firm puffballs all respond well to pickling.

Advantages - Marinated pickle broths give great flavors to mushrooms, taking bland varieties and giving them some excellent flavors. Great for parties, catered events, etc. As antipastos and hors d'oeuvres, etc. Relatively process to do at home.

Disadvantages - Recipes must be proven and techniques adhered to rigidly. Not a good medium for experimentation, as improper acid balance could lead to Botulism or other serious food poisonings.
7. Salting - Can be a preservation method in its own right or can be used to induce lactic fermentation. In Arora's All the Rain Promises there is an anecdotal reference and recipe for Lactarius deliciosis as done in Russia, I believe. It works and ferments the mushrooms well, but it yields a very salty product. Less salt risks spoilage before fermentation begins. When I brought some to an NMMS meeting, many did not mind the salt levels, others did; personal salt likes/dislikes are likely to come into play here.

Salting to "dry" mushrooms is a technique similar to salting anchovies and other fish. The water is drawn out by the salt and allowed to drain off or evaporate, leaving behind preserved product. Soaking re-constitutes product but often requires multiple rinses, and as mushroom flavor is lost this way, it is better to air dry mushrooms if moderate quantities or more are to be used. But for small amounts to bring up salt levels of a dish, this remains a very good method.

Advantages - Preservation stable and can actually change the cooking qualities less than full drying does, so some versatility exists here for texture with cooking. Easy to do and stable end product.

Disadvantages - mainly in high salt concentration forcing use of smaller quantities, or repeated rinses which leaches flavor needlessly. A first quick, but thorough rinse to remove salt before the mushrooms absorb much water helps to minimize this problem.

  • Copyright © 1999-2o17 by John Rahart & the New Mexico Mycological Society
  • First publication: NMMS News - March 1999
  • Most recent edition: 2ooo-1o-11
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