Preparing Mushrooms: The Topic

[Chris Hennes]

In the previous thread on removing mushroom gills the subject of washing mushrooms came up. According to Lauren Schiff, PR rep for the Mushroom Council,

The Mushroom Council recommends brushing off any dirt with a damp paper towel or fingers, rinsing only briefly under running water and pat dry with a paper towel. Never soak them, as they absorb moisture.

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There is some dispute as to the reasoning behind this advice. According to DCP:

According to tests run by Alton Brown of Good Eats, the bit about soaking appears to be a culinary myth.  Per his tests, 4 ounces of button mushrooms soaked in 1 liter of water for 10, 20, and 30 minutes gained 0.2, 0.25, and 0.15 ounces, respectively (about a teaspoon, max).  This works out to 3.75% to 6.25% gain.  The kicker?  Another 4 ounces of button mushrooms, subjected to a brief blast of cold water, gained 0.2 oz - same as when soaked for 10 minutes.

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My strong suspicion is that the dispute is due in large part to the differing behaviors of various types of mushrooms. Button mushrooms and shiitakes are quite different, for example. Last night I began some testing that I hope can become a collaborative eGullet effort to document the various "water absorption" properties of differing mushrooms over differing lengths of time.

Mushroom Type    Dry Weight    Wet Weight    Soak Time    % change
-------------    ----------    ----------    ---------    --------
Shiitake             76.0 g       104.6 g         60 s      +37.6%

I cannot state that this dramatic increase in weight had any particular impact on the finished dish, but for now that's not the point. Anyone else care to play?

ETA: My method here was to soak the mushrooms in cold water, swirling them around in it, for 60 seconds. I then took them out and laid them on towels, patting them dry. So the weight increase is not due to visible water on the surface of the mushrooms or in the gills (though the gills are challenging to dry completely).

Edited March 14, 2008 by Chris Hennes (log)

[dockhl]

So you only had them in water for a minute? Hmmm, I ALWAYS wash my mushrooms under running water, not soaking, and I don't think they absorb much. Weird.

[Fat Guy]

Mushroom type: white button

Dry weight: 149.0 g

Wet weight: 156.0 g

Soak time: 60 s

% change: +4.7%

There are some additional variables here. For example I made sure to shake the mushrooms thoroughly after soaking, in order to remove as much surface water as possible. I can think of a lot of seemingly minor issues that might affect results: age of mushrooms, temperature of water, etc. Also, I think the most revealing experiment will be to cook washed and unwashed mushrooms in order to compare their behavior and end results.

[melkor]

The "fresh" shiitake mushrooms you get at a grocery store are at best half dried by the time you purchase them. Candy caps absorb a fair bit of water when they're soaked but that's because they're often quite dry by the time they are harvested. Hedge hogs, yellowfoot, morels, oysters, porcini, chanterelles, and black trumpets don't absorb any noticeable amount of moisture unless they start out partly dried.

[Fat Guy]

I thought the 60-second time made sense. What happens in 10-30 minutes of soaking isn't relevant to actual cooking.

[Chris Hennes]

So you only had them in water for a minute? Hmmm, I ALWAYS wash my mushrooms under running water, not soaking, and I don't think they absorb much. Weird.

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I did not find the weight increase conspicuous until I weighed them, so it is possible that your mushrooms are gaining weight without you even noticing! And since I am sautéing them over very high heat, the water gain is eliminated quickly and doesn't affect the final dish, as far as I can tell. If you were to gently sweat them, however, I expect a 36% increase in water weight could make a big difference.

[melkor]

I can think of a lot of seemingly minor issues that might affect results: age of mushrooms, temperature of water, etc. Also, I think the most revealing experiment will be to cook washed and unwashed mushrooms in order to compare their behavior and end results.

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Every winter we forage and cook somewhere around 100 pounds of wild mushrooms. I'm lazy, my wife isn't. For everything but porcini, I use the sink or a bowl of cold water to clean mushrooms - I often just rub off or cut away anything that has too much dirt caked in it to be easy to clean. She uses a toothpick and a moist paper towel to carefully clean each mushroom. Mushrooms tossed in a hot dry pan will give off a fair amount of liquid, the quantity depends mostly on the type of mushroom. Mushrooms that have been washed rather than wiped clean give off a little bit more liquid, but not substantially more.

[melkor]

I thought the 60-second time made sense. What happens in 10-30 minutes of soaking isn't relevant to actual cooking.

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I'd agree that 10-30 minutes is irrelevant. But 60 seconds may not be long enough - it all depends how many mushrooms you're cleaning. I'd guess when I'm cleaning several pounds of small mushrooms like yellow foot or black trumpets that I end up leaving some in the water for two or three minutes.

[Chris Hennes]

I thought the 60-second time made sense. What happens in 10-30 minutes of soaking isn't relevant to actual cooking.

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I'd agree that 10-30 minutes is irrelevant. But 60 seconds may not be long enough - it all depends how many mushrooms you're cleaning. I'd guess when I'm cleaning several pounds of small mushrooms like yellow foot or black trumpets that I end up leaving some in the water for two or three minutes.

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I was only cleaning enough mushrooms for one serving atop a steak, so 60 seconds was plenty, I think. I'm not suggesting we all soak for 60 seconds, just that we keep track. If enough people participate I think the trends will be quite obvious. If you rinse, just indicate it in your post.

[melkor]

I was only cleaning enough mushrooms for one serving atop a steak, so 60 seconds was plenty, I think. I'm not suggesting we all soak for 60 seconds, just that we keep track. If enough people participate I think the trends will be quite obvious. If you rinse, just indicate it in your post.

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What will be obvious is the freshness of the mushrooms each person uses for this experiment. Mushrooms that have sat in cold storage for a month will double in weight when washed, fresh ones will gain an insignificant amount of weight.

[Chris Hennes]

What will be obvious is the freshness of the mushrooms each person uses for this experiment.  Mushrooms that have sat in cold storage for a month will double in weight when washed, fresh ones will gain an insignificant amount of weight.

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Even that is an interesting result: it would basically mean that the additional water added by washing the mushrooms is in fact bringing them back to their "correct" weight, in some sense. Therefore, if a recipe calls for 100g of mushrooms, that would be 100g after washing, not before.

[melkor]

What will be obvious is the freshness of the mushrooms each person uses for this experiment.  Mushrooms that have sat in cold storage for a month will double in weight when washed, fresh ones will gain an insignificant amount of weight.

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Even that is an interesting result: it would basically mean that the additional water added by washing the mushrooms is in fact bringing them back to their "correct" weight, in some sense. Therefore, if a recipe calls for 100g of mushrooms, that would be 100g after washing, not before.

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Isn't that another topic entirely? That would be more applicable in a thread about reviving poor quality ingredients. I don't see how different people measuring the weight gain of different age/quality mushrooms will lead to any sort of statistically valid conclusion...

[Chris Hennes]

What will be obvious is the freshness of the mushrooms each person uses for this experiment.  Mushrooms that have sat in cold storage for a month will double in weight when washed, fresh ones will gain an insignificant amount of weight.

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Even that is an interesting result: it would basically mean that the additional water added by washing the mushrooms is in fact bringing them back to their "correct" weight, in some sense. Therefore, if a recipe calls for 100g of mushrooms, that would be 100g after washing, not before.

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Isn't that another topic entirely? That would be more applicable in a thread about reviving poor quality ingredients. I don't see how different people measuring the weight gain of different age/quality mushrooms will lead to any sort of statistically valid conclusion...

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Yeah, probably. Of course, our sample size here is going to be too small to yield truly statistically valid results even under ideal mushroom-quality circumstances. Maybe we will find a pattern in the results, maybe we won't, and either way it won't be definitive. It will be one more data point. AB claims to have "busted the myth" of washing mushrooms, and he has done no such thing. Mushrooms, under some circumstances, do indeed gain significant weight when washed in water. Whether it matters is up for debate, of course.

[melkor]

Yeah, probably. Of course, our sample size here is going to be too small to yield truly statistically valid results even under ideal mushroom-quality circumstances. Maybe we will find a pattern in the results, maybe we won't, and either way it won't be definitive. It will be one more data point. AB claims to have "busted the myth" of washing mushrooms, and he has done no such thing. Mushrooms, under some circumstances, do indeed gain significant weight when washed in water. Whether it matters is up for debate, of course.

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AB and Harold are both correct that washing mushrooms is perfectly fine. What you are seeing in your experiment isn't valid for anyone working with good quality ingredients. Foragers, restaurants, and countless home cooks wash mushrooms. Fresh mushrooms don't absorb significant amounts of water. Dried mushrooms need to be soaked before use, the semi-dried mushrooms grocery stores stock may absorb water to replace whatever water they have lost in storage.

[slkinsey]

Exactly. With respect to supermarket mushrooms, I have found drying to be a consistent factor only with shiitake mushrooms -- which corresponds with Chris's results. As one might expect, I have also often found that supermarket shiitake mushrooms need some moisture in the pan to cook properly. Now, it's nice to be able to splash in some flavorful liquid (or fat) to be absorbed by the shiitake mushrooms, but nothing wrong with plain old water.

Really, though, I'm not sure that the question of moisture absorption from washing has any particular relevance to supermarket shiitake mushrooms. I've never found them to be particularly dirty or in need of cleaning of any kind, never mind washing or soaking in water. The only "dirt" is usually found at the very base of the stem where it is easy to cut off and discard. In fact, the stems of supermarket shiitake mushrooms are usually too dry and fibrous to use at all, and I often discard them entirely.

[DCP]

I thought the 60-second time made sense. What happens in 10-30 minutes of soaking isn't relevant to actual cooking.

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Agreed in that longer soak times aren't relevant to cooking, but not that they are entirely pointless. Scientifically, it does suggest that there is an upper limit to porosity, and that soak time need not be quantified. Of course, I'm particularly interested in the suggestion that soaking is equivalent to exposure to water, as suggested by Brown. (Though perhaps only for white buttons.)

[ricardoyudi]

reminds me about these posts by harold mcgee @ cheftalk

http://www.cheftalk.com/forums/open-forum-...-mushrooms.html

http://www.cheftalk.com/forums/open-forum-...ppy-shroom.html

(I hope it's okay to post other forums links)

[ChefJohnny]

I very rarely was cultivated mushrooms. If there happens to be a big chunk of dirt, I will obviously wipe it off. The only mushrooms I ever literally wash, are wild ones, since they are usually full of sticks and leaves and bugs, i.e. black trumpets, yellowfoots, etc. Generally, washing consists of putting the prepped mushrooms into a tall cambro (or similar tall container) and filling with warm water and thoroughly agitating the mushrooms in the water. I do this a couple of times with fresh water as the dirt and what not sinks. Lift the mushrooms out and drain on towels.

- Chef Johnny

Edited March 16, 2008 by ChefJohnny (log)

[austramerica]

I only ever buy the supermarket variety from the fresh food section but I do wash my mushrooms very briefly and leave them off to drain on top of paper towels while I prepare the other ingredients for my recipe. Anyway, if I am going to have mushrooms I prepare the mushrooms first before any other ingredients.

[annachan]

When I get mushroom, I find using a damp towel removes the dirt easier than soaking them in water or running water over them. I guess the towel gives it a little fraction that makes removing the dirt easier.

[Chris Hennes]

Over at the Cooking Issues blog Dave Arnold has a post up on soaking and cooking mushrooms in which he basically comes to the conclusion that not only do we WANT the mushrooms to absorb water, we should also crowd them in the pan when cooking. This flies directly in the face of the traditional cooking advice about mushrooms, but Dave's results show that the soaked and crowded mushrooms absorb significantly less oil and ultimately taste better:

As we expected, the soaked crowded mushrooms formed a soupy mess in the pan. The dry mushrooms didn’t stew and cooked quickly. Here is where it got weird. The dry mushrooms ended up absorbing all the oil. [...] When the soaked and crowded mushrooms had finally evaporated all their extra water and stated to sauté, they didn’t absorb all the oil. When they were finished, a significant amount of oil was left in the pan. They tasted better and less oily than their dry cousins –by a lot.

[Shamanjoe]

This is interesting. Until very recently I haven't been a fan of mushrooms at all. The first time I cooked them myself was only a few months ago. When I did though, I got a few different varieties from Whole Foods and washed them up. They sautéed just fine, and I didn't notice any appreciable difference between mine and restaurant mushrooms.

When I get some again, I'll post the washing details and weights.

[Shalmanese]

I just now tried the Wet & Crowded Mushrooms technique from the cooking techniques blog and, wow, what a revelation it is! Unlike conventional fried mushrooms, these things barely absorbed any grease at all and there was a pool of fat at the bottom of the pan at the end of cooking. I can't believe I've been struggling with sauteed mushrooms all these years when something so simple turns them into something sublime.

[Abra]

Interesting and counter-intuitive. I'll try it this week.

[JAZ]

Oddly, considering it's Dave and Nils from Cooking Issues, they don't seem to have done a complete job of testing all the variables. What happens, for instance, if you soak mushrooms, but then don't crowd them in the pan? Or don't soak them, but do crowd them? That is, with two variables (soaking and crowding) don't you need four tests instead of two?