An angel food cake has no butter, no baking powder and no yeast in it. The meringue on a lemon pie is egg white and sugar. A souffle rises because the air beaten into its whites expands in the oven. In each case, beaten egg whites foam up and give the dish its structure, and there is no crumb underneath to take over if the foam gives way.
Beat the whites too long, or bake them too hot, and the foam turns grainy, sheds its air and dissolves into a puddle. The proteins have clamped together tightly enough to wring out the water they were holding. Meringue weeps. Souffle sinks.
For roughly 200 years, kitchens that cared about this beat their whites in unlined copper bowls, and the reason cooks gave was that the copper acidified them. It does not. But the bowl does something. A 1984 paper in the journal Nature traced the effect to the metal itself, and silver bowls turned out to work as well, so the working explanation now is that soft metals keep the reactive sulfur groups from locking to each other.
Cream of tartar has the same effect that the old cooks credited to the bowl. Cream of tartar is an acid. About an eighth of a teaspoon per egg white lowers the pH and changes the electrical charge the proteins carry so they line up around air bubbles instead of clenching together.
No acid fixes the one real ruin, which is a speck of yolk. Fat stops the foam from forming at all. No matter what the bowl is made of, it has to be spotless and dry.
Rick Good spent ten years in the newspaper business, including with The News & Observer (Raleigh, NC) and The Greenville News (Greenville, SC). He co-wrote, with Melinda Coleman, Rutledge to Riley: Governors of South Carolina, 1776–Present (Published by The Greenville News), and is the author of Mind Games Trivia #1 (Amazon). He has recently spent 15 years creating original trivia content through Sounds Good Mobile Entertainment and continues that with his new company, SGME Software. He edits The Smart Reader’s money, real estate, and business coverage.
