The Food Lab: Better Home Cooking Through Science

supersaturated with liquid—there’s more liquid in
there than it can hold on to—so when you slice it
open, all that extra liquid pours out. By resting the
steak, you allow the liquid that was forced out of the
edges and into the center time to migrate back out to
the edges.
Seems to make sense, right? Imagine a steak as a
big bundle of straws, representing the muscle fibers,
each straw filled with liquid. As the meat cooks, the
straws start to change shape, becoming narrower
and putting pressure on the liquid inside. Since the
meat cooks from the outside in, the straws are
pinched more tightly at their edges and slightly less
tightly in their centers. So far, so good. Logically, if
the edges are pinched more tightly than the center,
liquid will get forced toward the middle, right? Well,
here’s the problem: water is not compressible. In
other words, if you have a two-liter bottle filled to
the brim with water, it is (nearly) physically
impossible to force more water into that bottle
without changing the size of that bottle. Same thing
with a steak.
Unless we are somehow stretching the centers of
the muscle fibers to make them physically wider,
there is no way to force more liquid into them. You
can easily prove that the muscle fibers are not
getting wider by measuring the circumference of the
center of a raw steak versus a cooked one. If liquid
were being forced into the center, the circumference
should grow. It doesn’t—it may appear to bulge, but