Souffle's that work always seem like magic, and things that work by magic do not always inspire confidence, magic not being particularly dependable. But souffles aren't magic. Steel yourself for the unromantic news: souffles, puff and billow through they might are nothing by chemistry in action.
What takes a souffle' to great heights and then keeps it there -- at least temporarily -- is a combination of air, heat and the proteins present in egg whites.
Like other seemingly magical events, the rising and falling of souffle's has over the centuries become surrounded with a certain amount of lore. One old chef's tale holds that egg whites should be beaten in unlined copper bowls, because something about the copper makes them rise higher and stay there.
Because the chefs had no food chemistry background it was easy for the more scientifically inclined to go "bah!" But Shirley Corriher, a determined cooking teacher and food writer who travels around the country teaching, among other things, a vastly popular food science course, decided to put the chefs' theory to the test.
Corriher and some coworkers beat 20 batches of egg whites in bowls of every conceivable material, and with different kinds of beaters. "We tried to measure the diffences in volume," says Corriher, "but we couldn't see a lot." It looked like the chefs were all wet.
However, they then turned the egg whites into souffle's by folding them into a "souffle' base," a combination of thick bechamel, egg yolks and flavorings. And when the souffle's were done, the differences became clearly apparent. Those made from egg whites beat in unlined copper bowls rose almost twice as high. Now it was looking like the chefs were right.
When Corriher took her findings around to scientists, most of them said, in essence, "that's nice, dear, but it's impossible." But her inquiries stimulated discussion among people who research such things, and since then Corriher's experiment with egg whites and souffle's has been validated scientifically, especially by Harold McGee, whose book "On Food and Cooking" has recently been published by Scribners.
The facts are in: souffle's made from egg whites beaten in a copper bowl rise significantly higher, which, after all, is the point of souffle's.
Here's how it works: when egg whites are beaten, air bubbles are trapped by a coating of conalbumen, a protein, and the whites get fluffy. Conalbumen and copper, as it turns out, love each other. And when trace amounts of copper combine with conalbumen, they provide a more stable coating for the air bubbles so that they are less likely to break down.
Then, in the oven, heat makes the air bubbles in the souffle' expand further, and here again the copper-conalbumen combination is a winner. It seems that the combination has a higher coagulation temperature than conalbumen alone so that the air bubbles can expand for a longer period of time before they set, or coagulate. Voila, a fluffier, more ethereal and more spectacular souffle'.
"And now," says Corriher, her sweet theories proven by the hard sciences, "nobody can ever tell me that the copper bowl didn't matter."
Corriher says that she found the egg whites profit from four or five minutes' exposure to the copper for maximum effect. So she usually beats them first with an electric beater, then finishes them off by hand with a whisk. Beating egg whites solely by hand is not that difficult or tiring an operation, however, and with a balloon whisk it doesn't take much longer than it does with the help of electricity.
Although the copper bowls are unlined, there is no need to worry about the toxic reaction that can occur when you cook or store foods in unlined copper, particularly tarnished copper, because the copper and the whites aren't together long enough to cause trouble.
To clean such a bowl, rub a little salt and vinegar around in it, then rinse and wipe dry. You can also clean it with copper cleaner, but be sure to rinse it very, very well, since copper cleaners generally smell like a petrochemical factory and probably taste that way, too.
Copper mixing bowls usually have rounded bottoms, the better for beating with, and handles to keep ahold of to keep them stable. Copper liners are available to fit the bowls of the venerable KitchenAid electric mixer, although they aren't made by KitchenAid. Kitchen Bazaar carries both the bowls and the liners.