What Einstein Told His Cook (34 page)

YOU CAN’T WASH YOUR CAR WITH A WET MUSHROOM

All the cookbooks say that one should never wash mushrooms because they soak up water like a sponge and that we should give them only a quick rinse or simply wipe them off. But aren’t they grown in manure?

S
oak up water? Not true. Those books are wrong.

Grown in manure? I’m afraid so.

First, let’s deal with the manure.

The common white or brown button mushrooms in the supermarkets (
Agaricus bisporus
) are cultivated in beds, or so-called substrate mixtures, that can include anything from hay and crushed corncobs to chicken manure and used straw bedding from horses’ stables.

That knowledge bothered me for many years. Repeatedly warned against waterlogging my mushrooms by giving them a bath, however, I resorted to a soft-bristled mushroom brush that presumably whisked away the nasties from dry mushrooms without bruising them. It didn’t do much. I sometimes even peeled my mushrooms, a time-consuming pain in the neck.

But as the hymn “Amazing Grace” would have it, “
I once was lost but now am found; was blind, but now I see
.” I know now that the mushroom growers compost their substrate material for fifteen to twenty days, which raises its temperature to a sterilizing level. The compost, regardless of its origin, is germ-free before it is “planted” with the mushroom spores.

Nevertheless, I can’t help thinking that there is more to manure than germs. So I still clean my mushrooms. And yes, I wash them in water, because they don’t absorb more than a tiny bit, as I’ll show below. Moreover, I seriously doubt that a water wash removes flavor, as some books claim. That would be true only if their flavor resided mostly on the surface and was predominantly water soluble.

I was always suspicious of the sponge model of mushroom flesh because it never appeared to me to be the least bit porous, even under a microscope. (Yes, I did that.) When I read Harold McGee’s book
The Curious Cook
(North Point Press, 1990), I felt vindicated. An equally suspicious type, McGee weighed a batch of mushrooms, soaked them in water for five minutes—about ten times longer than any washing would take—wiped them off and weighed them again. He found that their weight had increased very little.

I have repeated McGee’s experiment with two 12-ounce packages of white
Agaricus
mushrooms (a total of 40 mushrooms) and a 10-ounce package of brown ones (16 mushrooms). I weighed each batch carefully on a laboratory scale, soaked them in cold water with occasional stirring for McGee’s five minutes, threw off most of the water in a salad spinner, rolled them around in a towel, and weighed them again.

The white mushrooms, all tightly closed buttons, had absorbed only 2.7 percent of their weight in water. That’s less than three teaspoons of water per pound of mushrooms, in agreement with McGee’s result. The brown mushrooms retained more water: 4.9 percent of their weight or five teaspoons per pound. That’s probably because their caps were slightly separated from the stems and water was trapped in the gill spaces, not because their flesh is any more absorbent. Many other irregularly shaped vegetables would mechanically trap small amounts of water. And the timid “quick rinse” recommended for mushrooms by many cookbooks might trap just as much as my five-minute soak did.

So go ahead and wash your mushrooms to your heart’s content—at least the common button kind; I haven’t tested any of the more exotic varieties. But bear in mind that any brown dirt you see isn’t manure; it’s probably sterilized peat moss, with which the growers cover the composted substrate and through which the mushrooms actually poke their little heads.

And by the way, if you find your mushrooms releasing so much water in the sauté pan that they are steaming instead of browning, it’s not because you’ve washed them. It’s because the mushrooms themselves are almost entirely water and you’ve crowded them so much in the pan that the expelled steam can’t escape. Sauté them in smaller batches or use a bigger pan.

GRAMPA’S FOLLY

S
top! I hope I caught you before you put Grandma’s reputed wisdom to the test. There is no scientific basis whatsoever to the silver dollar trick. It’s nonsense. I’d call it an old wives’ tale, except that women who lived to be old wives never believed it.

There is no simple way of distinguishing poisonous mushrooms from safe ones, except by knowing and identifying the species. There are tens of thousands of known species of mushrooms, and many of the poisonous ones look very much like the edible ones. I personally don’t have a good visual memory for shapes, so I permit myself to pick only two or three species that have no evil twins. I let the experts (or my favorite restaurants) supply me with the cèpes, morels, chanterelles, porcini, shiitake, enoki, and oyster mushrooms that have so enlivened American cuisine in recent years.

Incidentally, those ubiquitous portobellos that are on every menu these days are not a separate species; they’re common brown
Agaricus
mushrooms that have been allowed to grow big before harvesting.

Your grandfather did your father a disservice, if I may say so, by letting him believe the silver coin test. He simply knew his mushrooms.

KEEPING COPPER PROPER

I recently purchased a set of copper cookware and it looks great. How can I keep it looking new?

S
hiny copper is beautiful, and there are some wonderfully effective polishes on the market. But are you a cook or a decorator? The great virtue of copper or copper-clad cookware is that it conducts heat superbly and evenly. For that it deserves to be cherished, not polished. If you try to keep your copper cookware in its virginal state you will have taken on a full-time job.

But to avoid having them look too blotchy, there are a few simple things you can do. Don’t ever put them in the dishwasher; the highly alkaline detergent can discolor the copper. Dry them completely after washing with dishwashing liquid. Make sure to get all the grease off with a mildly abrasive cleaner, because when heated it will burn into a black stain. Finally, don’t heat the pans too hot, either with oil in them or especially when empty. Dark copper oxide forms most readily on the hottest spots, and you may wind up with the pattern of the burner imprinted on the pan’s bottom.

MEASURE FOR MEASURE

WHEN AN OUNCE IS NOT AN OUNCE

Why do we have different measuring cups for wet and dry ingredients? A cup of sugar is the same volume as a cup of milk, isn’t it?

T
hat depends on what your definition of “is” is.

A cup is indeed a cup throughout the land: eight U.S. fluid ounces, whether wet or dry. But you may be wondering: If a fluid ounce is a measure of fluids, how come we use it also to measure flour and other dry solids? And what’s the difference between an ounce of volume and an ounce of weight?

The confusion stems from our antiquated American system of measurements. Here’s what we were supposed to have learned in school (pay attention now, and follow the bouncing ounce): A U.S. fluid ounce is an amount of volume or bulk and is to be distinguished from a British fluid ounce, which is a different amount of volume, both of which are to be distinguished from an avoirdupois ounce, which is not an amount of volume at all but an amount of weight and is to be distinguished from a troy ounce, which is a different amount of weight and is
not
to be distinguished from an apothecary’s ounce, which is exactly the same as a troy ounce except in February, which has 28. Is that perfectly clear?

Now if that isn’t an argument for the International System of Measurement, known throughout the world as the SI, for
Système International
in French and to us as the Metric System, I don’t know what is. In the SI, weight is always in kilograms and volume is always in liters. In the entire world, the United States is the only nation still using what used to be called the British system of measurement until even the British abandoned it and went metric.

Let’s rephrase your question. Aren’t eight good old American fluid ounces of milk the same amount of volume as eight good old American fluid ounces of sugar?

They certainly are. We’d really be in trouble if that weren’t the case. But we still need a set of glass measurers for liquids and a separate set of metal measurers for solids.

Try to measure out a cup of sugar in a two-cup glass measurer and you’ll have a tough time judging exactly when the sugar reaches the one-cup mark, because the sugar’s surface isn’t completely level. But even after you tap it on the counter to flatten it out and adjust it exactly to the mark, you won’t have the amount of sugar that the recipe intended. That’s because the recipe tester used a metal, one-cup “dry” measurer, filled flat to the brim. And believe it or not, that gives you a different amount of sugar than if you measured it out in a glass measurer.

Try it. Measure out exactly one cup of sugar by slightly overfilling a one-cup metal measurer and scraping off the excess with a straight edge, such as the back of a large chef’s knife. Now pour the sugar into a two-cup glass measurer and jiggle it until the sugar’s surface is flat. Betcha it doesn’t come fully up to the one-cup line.

Could that be due to inaccuracies in the measuring cups themselves? Not unless you’re using a flea-market special, with lines that look as if they were hand-painted in kindergarten; reputable kitchenware manufacturers are pretty careful about the accuracy of their products. No, the answer lies in a fundamental difference between liquids and granulated solids such as sugar, salt, and flour.

When you pour a liquid into a container it flows down into every crevice, leaving no spaces, not even microscopic ones. But a granulated solid can settle unpredictably, depending on the shape and size of the grains and of the container. Generally, when poured into a wide container, the grains get a chance to spread out more and fill in the spaces beneath them, so they settle down more compactly than if they were stacked up in a narrow container. And because they are settled more densely, they occupy less volume. The same weight of sugar will therefore actually occupy less volume in a wide container than in a narrow one.

Back to the kitchen and to your measuring cups. Dollars to doughnuts you’ll find that at the same capacity level, the diameter of your glass measuring cup is substantially wider than the mouth of your metal one. Therefore, sugar and especially flour, which is notorious for its erratic settling, will occupy less volume in the glass measurer. If you use a glass measurer for your dry ingredients, you’ll be adding more than the recipe intended.