To Information-Hungry Author Harold Mcgee, Food Is Something to Pinch, Poke and Probe
McGee, whose eclectic credentials include a B.S. from Caltech in literature and a Ph.D. in English literature from Yale, lives in Palo Alto with his 33-year-old wife, Sharon Long, a biologist. Between sips of soda at his three-bedroom tract house, McGee, 33, discussed with reporter Dianna Waggoner nearly everything from why corn pops to why meat tenderizers don't work.
Did childhood experiences lead to your interest in food science?
Not really, though food was certainly a pleasant experience when I was growing up. When my mother would broil a chicken or make spareribs, there was always this gooey coating in the bottom of the pan afterward. It had such a wonderful, intense flavor that we kids always fought over it. My mother finally caught on to a solution. After the meal all four of us would line up and she would dispense the scrapings—as we called them—in quarter-tablespoon servings. It was a lot like taking Communion. You'd get your mouthful and then walk back to the end of the line and wait for more. I would savor it as long as I possibly could. It was only when doing research on the book that I understood why the scrapings were so good: They were the products of browning reactions. For Sunday dinner we always had sandwiches and popcorn. From door screening, my dad devised a top to cover the pan. We used to gather around the stove and watch the corn exploding, it seemed, right in our faces.
Why does over cooking vegetables make them mushy?
Pectins and hemi-celluloses, which act like cement, can be leached out of vegetable cell walls by hot water. In overcooking you will remove too much of these compounds.
What is the best way to help a banana ripen?
Some fruits put out a lot of ethylene gas during the ripening process. Just put a ripe banana in a bag with an unripe one and the ripe one will stimulate the other to maturity.
What makes popcorn pop?
In some kinds of corn the protein is a very hard, shell-like layer just under the skin of the kernel. The center of the kernel is an area mostly taken up by starch granules. When water within the kernel gets to the boiling point, it vaporizes, expands in size and enters the starch granule. This causes the starch to soften and expand. Forces inside the center keep building, because the protein shell holds things back for a while. Eventually, the kernel is blown open by the force. The water vapor expands the starch granule and protein into the white stuff of the popped corn.
Why do some fruits turn brown?
They contain two sets of chemicals—one an enzyme, the other the compound the enzyme acts on. When these fruits are cut or injured, the enzyme causes the compound to line up in long, dark chains. All acids prevent these chains from forming, so a little lemon juice squeezed on fruit will stop it from turning brown.
Why are some parts of meat more tender than other parts?
As a general rule, younger animals and the less exercised parts of an animal are more tender. Exercise causes an increase in the amount of tough connective tissue, as well as in the density and thickness of the muscle cells themselves. When you chew the muscle, you have more to get through.
Does this also explain why animals have both dark and white meat?
The reasons are related. Frequently used muscles store oxygen by means of the red pigment called myoglobin. The more heavily the muscle is used, the more myoglobin it contains. Chickens, for instance, which do a lot of standing around but no flying, have dark legs and white breasts. Wild ducks, on the other hand, spend a lot of time on the wing and have a lot of dark breast meat.
Why does cornstarch thicken sauces?
When cornstarch—which is 90 percent starch—is added to a hot liquid, its starch granules expand. As they expand, they bump, join and trap liquid in the networks they form.
How do meat tenderizers work?
Not very well. Commercial meat tenderizers are a preparation of enzymes produced by plants—figs, pineapples and papayas—that break down protein. The problem is that in order to work, the enzyme has to come into contact with the protein. When you sprinkle some of this stuff onto a piece of meat, it only touches the surface. What you get is a mushy surface and a tough interior. Even if you were to use a fork to break inside, you would be doing as much good by mechanically breaking up the muscle bundles as the tenderizer is doing. Pounding is really the only effective way to tenderize meat.
Why does milk burn so easily?
The proteins in milk are combined in very large particles. When heated, these clump together in heavy bunches that sink to the bottom of the pan, where they first brown and then char.
Every cook knows that searing meat on the outside before cooking helps seal the juices in. Exactly how does this process work?
Like meat tenderizers, it doesn't. Experiments have shown that you actually lose more fluid by searing meat than by cooking it at a stable, low temperature. Searing does, however, create flavor.
Let's try one more. Are fertilized eggs more nutritious than infertile?
Another myth, I'm afraid. Despite beliefs to the contrary, neither shell color nor the fertilization of the ovum has any nutritional significance. A fertilized egg contains only a microscopic embryo whose development has been arrested by refrigeration.
Surely some of the food legends proved true. We understand, for example, that you were able to duplicate the recipe of the first-century-A.D. epicure Apicius for transforming red wine to white by adding soda, egg white or the ash of grapevines.
Not quite. I added a bit of each substance to glasses of red wine I lined up on my kitchen windowsill. Within a few days they turned—but not white. More like brown or an unpleasant blue. And the taste was just awful. It's not to be recommended.
Were there any food mysteries that resisted your probing?
Many. To take one example, bread dough is still pretty much of a mystery. People have a good idea what the proteins are doing, but we know that adding just the tiniest amount of fat will make the bread much lighter. No one knows what's really going on. Chemical analysis is a very powerful analytical tool, but there are so many chemicals involved that we'll probably never know the final truth about a lot of the processes. Caramelization is so complex, for example, that it is going to take a lot of time simply to categorize all that's happening. You can start with one chemical and perhaps end up with more than 100 of them.
Why do onions make us cry?
Enzymes in the onion act on a sulfur compound. The resultant volatile substance leaves the onion, flies through the air and enters the cook's eyes, breaking down into sulfuric acid.
What is the weirdest subject anyone asked you to investigate?
Most of the questions were ordinary—which vegetables have the most types of particular vitamins, or how to cook them. The most unusual was the "fart chart" question that started the whole thing.