Cakes & chemistry: the science of baking

Article from theColumbusDispatch


It’s one of the first lessons in culinary school: Baking is a science.
Any slight changes in a recipe — too much baking powder, over-mixing a batter — can make the difference between a moist cupcake and a hockey puck.
“There is definitely an art to baking,” said Yael Vodovotz, a food-science professor at Ohio State University. “There’s a science to it, too.”
At Ohio State’s Food Science and Technology Department, Vodovotz’s research focuses on healthful, functional foods that might help prevent chronic diseases. For example, she has worked on a soy-based bread with properties designed to combat prostate cancer.
“Food is very complicated,” Vodovotz said. “A lot of our (food-science) students go through pre-med because it’s heavy in the basic sciences.”
Take cakes, for example. Each ingredient has a job to do. Flour provides the structure; baking powder and baking soda give the cake its airiness; eggs bind the ingredients; butter and oil tenderize; sugar sweetens; and milk or water provides moisture.
Combining the dry and wet ingredients puts them to work — the proteins in the flour bond and create gluten, giving the cake its flexibility. Eggs hold the mixture together. Baking powder and baking soda each release carbon dioxide, adding bubbles to the batter, helping it expand.
It’s important to mix dry ingredients in the right order, Vodovotz said. Each dry element is competing for water.
“Depending on which is the stronger competitor is where the water will favor,” she said. “If you put in the wrong ingredients first, (the batter) will tend to clump because then they don’t have enough water.”
A cake batter that flows means that the hydration is consistent. But be careful not to over-mix, Vodovotz said.
“When gluten aligns, the proteins align with strands,” she said. “If you keep mixing, it will be too runny, and it won’t hold. You’ve disrupted the networks that are formed.”
The ingredients change again when the batter is in the oven. The starch portion of the flour gels — with help from sugar — and creates a weblike structure that traps water and provides moisture. The carbon dioxide from the baking powder or baking soda will expand the cake. Gluten holds those bubbles in place (think of a balloon that contains air) while the fat from the oil or butter lubricates the process.
“When it bakes, the whole protein network hardens and holds the bubbles in cakes,” Vodovotz said. “That’s why when you take a cake out early, the cake can collapse because a structure hasn’t set yet.”
Also, if there is too much baking powder or baking soda, the bubbles will float to the top and pop, sinking the cake. Adding too much also can give a baked good a chemical taste.
Sugar and fat also play a role when a cake cools, Vodovotz said. Sugar helps slow the cake from hardening. When a cake begins to go stale, the starch starts to crystallize. Sugar will draw the water and prevent the starch molecules from forming and crystallizing. Higher fat content will keep a cake moist longer, holding off staleness.
Putting baked goods in the fridge, however, has the opposite effect. Lower temperatures will cause the cake to go stale quicker, Vodovotz said.
Think of baking as a lab experiment, said Patricia Christie, a chemistry lecturer at Massachusetts Institute of Technology who taught a Kitchen Chemistry class for 12 years. The class served as an undergraduate chemistry lab. Most experienced home cooks follow a recipe the first time they use it but alter it the next time based on results, she said. “You’re performing the scientific method to the recipe. You are making an assumption, testing the theory and coming up with a conclusion.”
She points to boxed cake mixes, which say 50 to 75 strokes are needed to mix the batter.
“They have cooks test recipes,” she said. “One person mixes it 40 times; another person, 60 times; and another person, 100 times, to figure out the best range.”
In one lab assignment, students created meringues for lemon meringue tarts in copper bowls because the copper ions help stabilize the meringue.
“You can always tell when the meringue is done,” Christie said. “The foam stays still.”
Students at Columbus Culinary Institute are not taught cooking methods at the molecular level, but they cover the basic science behind techniques and ingredients.
For example, you don’t use high-protein flour when making a cookie. (High-protein flour has more gluten than all-purpose flour and is better suited for bread, in which it gives strength and structure. Cookies don’t need that.)
And butter for a pie crust has to be cold. (You want the fat to coat the flour, not blend in with it. Otherwise, the crust will get soggy and won’t have a crisp, flaky texture.)
“I tell my students, ‘If you know the ingredient and how it behaves, you have a better chance of success,’ ” said Laurie Sargent, the institute’s lead pastry instructor.