Water 100% 103.2%
As you can see, while a plain chicken breast lost
about 17 percent of its moisture during cooking, a
brined breast lost only 10 percent. Salted breasts
came in just under brined breasts, at 11 percent.
Soaked in plain water, the breasts gained about 3
percent in weight prior to cooking, but all of that
extra water came right back out—water-soaked
breasts fared no better than plain breasts.
From this data, we know that salt is doing
something to help retain moisture, whether applied
through a brine or simply rubbed on the surface of
the breasts. How does it accomplish this? It’s the
same as salting a steak before you cook it: it’s in the
shape of the proteins. In their natural state, muscle
cells are tightly bound within long protein sheaths—
this doesn’t leave much room for extra water to
collect in the meat. But as anyone who has ever
made sausages or cured meats knows, salt has a
powerful effect on muscles (see here). A salt solution
will effectively denature (read: unravel) the proteins
that make up the sheath around the muscle bundles.
In their loosened denatured state, you can fit more
water into those muscles than in their natural state.
Even better, the denatured proteins in the sheaths
contract far less as they cook, squeezing out much