Why does a cookie crumble?
The short answer: A cookiequake.
The long answer: In a "they-got-paid-to-do-this?" type of study, physicists from Great Britain's University of Loughborough in Leicestershire carried out laser tests on cookies. (Or, as they call them in Britain: biscuits.) After cookies come out of the oven and begin to cool, moisture gathers around the rim. That moisture causes the cookies to expand. But at the same time, moisture forming in the center of the cookies causes them to contract. Expand. Contract. Expand. Contract. These opposing forces build up and build up and finally cracks appear in the cookies, which weaken them. The problem is even worse in low-fat, low-sugar cookies. These cracks--or cookie fault lines--cause the cookies to break easily when they are handled, moved, or packaged. Hence, the cookiequake.
The researchers, led by doctoral student Qasim Saleem, figured this out by bouncing a laser beam off the just-baked cookie surfaces as the temperatures dropped during the cooling process. Nature News Service reports that interference between light rays scattered off the rough surfaces produced a speckled pattern in the reflected light. The pattern changed as the stresses deformed each cookie's shape. This is the same process geophysicists use when they study earthquake zones using airborne radar.
Saleem says the study findings will help cookie manufacturers change the cooling process to limit the moisture that develops and stop the cracks before they form. The findings were published in the journal Measurement, Science, and Technology.
We're thinking researcher Qasim Saleem is brilliant. He's figured out a way to get all the cookies he wants while he works!