November 26, 2002
Sumptuous Servings of Food and Chemistry
|Gary Tramontina for The New York Times|
|"I love what I do," says Dr. Robert L. Wolke, 74. "I'm teaching people about two things I'm passionate about, food and science."|
When Robert L. Wolke comes to your house, you want to give him something nice to eat.
Dr. Wolke, 74, is a retired University of Pittsburgh chemistry professor and researcher who discovered the longest half-life radioisotope known, cadmium 113. He also is a leading writer about the corners where chemistry and cooking meet.
In addition to producing academic textbooks, he has published several popular works on science in everyday life, including "What Einstein Told His Cook: Kitchen Science Explained," published in May. He also writes a twice-monthly syndicated newspaper column, "Food 101."
But on this particular afternoon, he has already had his lunch. So the talk is about his work.
"I love what I do," Mr. Wolke said. "I'm teaching people about two things I'm passionate about, food and science. To me, science is nothing more than what's going on around us as we carry out our daily activities. Food and cooking are gold mines of everyday science."
Q. How did you develop this odd beat, the chemistry of food?
A. I grew up in Brooklyn during the Depression, and food wasn't important in our house, except that there'd be enough of it.
I knew nothing about fine cuisine until I went to graduate school in nuclear chemistry at Cornell. They had a school of home economics there, and it had a cafeteria which was cheap and wonderful. Going to that cafeteria opened up the world of food to me. I experienced things I had never seen before: eggplant, Camembert cheese.
So then, as a young professor, I moved around the country a bit and did a lot of cooking. In my first marriage, my wife hated food and cooking. Food meant only one thing to her: calories.
Another thing: I liked to write, and I'd moonlight from the academic world by submitting humor articles to newspapers and they'd get published. Eleven years ago, I met my current wife, Marlene Parrish, a food professional, and my writing started turning toward food because of our shared interest.
About five years ago, I pitched a story to Nancy McKeon, who was then food editor of The Washington Post. She replied: "I can't use the story but I like your style. Let's see if we can work together."
Q. How did you manage to meld your writing career with that of being a respected academic? In the subculture of the academy, "popular" writing is not necessarily respected.
A. It was thought of as "frivolous." Arghhh! Every year when I'd have to submit my list of publications, after I'd put down my research publications, I'd write "other" rather stating, "humor piece in the Sunday supplement." And you know, I was really proud of some of my non-chemistry publications! This column, which deals with chemistry and cooking, is finally a way of putting these two parts of my life together.
Q. What are some of the things you've uncovered as a food writer? For instance, we understand you devised an experiment to determine the most efficient means of extracting juice from a lemon?
A. It's supposedly common knowledge that if you want to get the most juice out of a lemon, you roll it on the table before squeezing. Another school has it that you put the lemon in the microwave oven for 30 seconds and then squeeze.
Well, I got myself a case of limes and set up four test groups. One, I rolled the fruits on the table, another I microwaved, a third I did nothing to, and a fourth, I microwaved and rolled on the counter. Then I cut the limes in half, squeezed them out and counted the number of milliliters of juice per gram of fruit. Rolling accomplished nothing, as did microwaving. But if you rolled and then microwaved, you got somewhere between 20, 30 percent more juice.
Q. In another experiment, you discovered that it might be easier to cook an egg on a dark blue Taurus than on a Texas sidewalk. Why learn this?
A. In the summers, when people get tired of saying, "Is it hot enough for you," they often say, "It's so hot that you could fry an egg on the sidewalk." I decided to find out if this was really possible.
My daughter lives in Austin, where it gets pretty hot, and one year during a visit, I brought along a noncontact thermometer to read the temperatures of various surfaces. So when it got to be about 100 degrees out, I measured the temperatures of sidewalks and black asphalt paving. I never found anything close to what is required to congeal an egg — about 158 degrees.
Now, my daughter's car, which was dark blue, seemed a better bet. I reasoned that in principle, when you break an egg on a metal surface, that surface won't cool down as much. The heat will be replenished by heat conduction through the metal. And indeed, a reader later told me about seeing a movie where Germans in the Afrika Corps fried eggs on the fender of their tank. If it gets hot enough and it's on a surface that's a good enough conductor of heat, I decided it can be done.
Q. You've investigated whether human belching contributes to global warming. Does it?
A. It actually might. After reading about how many billions of gallons of carbonated beverages are consumed in this country every year, I asked myself what happens to all of that carbon dioxide. CO2 is a greenhouse gas. Some of the carbon dioxide goes directly into the atmosphere from the opened containers, and the rest must be either breathed or belched out by the drinkers.
I found out the pressure it takes to fill all these bottles and cans, and calculated how much carbon dioxide would be equivalent to that pressure. It turned out to be about 800,000 tons.
Q. Don't your calculations assume that the gas is all brand new CO2 that has been specifically manufactured for the carbonated drinks?
A. I made rough corrections for that. If the gas was made by heating limestone, which much carbon dioxide is, then it's brand new in the atmosphere. But in alcoholic beverages like beer, the CO2 comes from the fermentation of grains, which took the carbon dioxide originally from the atmosphere by photosynthesis, so it doesn't count as brand new. And some of the CO2 in soda pop is obtained from the air, so it gets pretty complicated. All in all, carbonated beverages don't seem to be much of a threat to the planet.
Q. Since we are on the subject of beverages, can you explain why tea made in the microwave almost always tastes awful?
A. You need very hot water to get the maximum flavor and color out of tea. That's why the British go as far as to preheat teapots. Heating a cup of water in a microwave oven is not a uniform process. Some parts of it may be boiling and others are not. When it looks as if it is boiling, it is just not hot enough to take the flavor out of the leaves.
Q. What can science teach us about the chilling of martini glasses?
A. A good bartender will always chill the martini glass because it should be as cold as possible. And what they will do is put ice water in a glass and let it sit for a few minutes while they are mixing the martini, then dump the ice water out and pour the martini in.
I say that's not as good a method as it could be. Ice water can never be colder than 32 degrees or else it wouldn't be water, it would be solid ice. So I say, don't chill it with ice water, chill it with cracked ice because ice straight out of the freezer can be something like 10 below zero. Much colder. Unfortunately, though, bartenders' ice usually isn't anywhere near that cold because it's been sitting out for some time.
Q. Should cooking schools give their student chefs a basic chemistry course?
A. To some extent. But it needn't and shouldn't be a separate course, such as we get in high school or college, with all that math and balancing of equations stuff. It should be here-and-there, now-and-then bits of chemistry or physics, applied to specific food and cooking situations on a "need-to-know" basis.
Q. What is it about the chemistry of turkey that makes it such a potential public health hazard?
A. It's not so much the chemistry as the physics, and it's not so much the turkey as the stuffing.
A turkey is shaped physically like a big round ball, and when you're roasting it the heat has to come in from the outside. That makes the inner parts of the turkey the last to become hot enough to kill dangerous bacteria; the U.S.D.A. recommends at least 165 degrees.
But by the time the inner thighs get to that temperature, the breast is overcooked. And if the bird is stuffed, the stuffing may never get that hot, and at lower temperatures stuffing is a wonderful growth medium for bacteria.
So what can you do to avoid poisoning your family or winding up with a dried-out, overcooked turkey? You can bake the stuffing in a separate casserole dish instead of burying it inside the bird.
But the best suggestion I've heard is to place the stuffing in the roasting pan beneath the turkey. It can then cook thoroughly, and the drippings will flavor it. I haven't tried this yet, and I wonder if you might not wind up with greasy, mushy stuffing. Also, it kills the possibility of making pan gravy. But I guess you can't win 'em all. Not until they breed flat turkeys.