The Food Lab: Better Home Cooking Through Science

Remember how collagen looks like a twisted piece of
yarn? Have you ever tried separating the separate strands in
a piece of yarn? It’s possible but time-consuming, and that’s
exactly what’s going on in a pot of simmering connective
tissue. At a 190° to 200°F simmer, it takes about 3 hours for
90 percent of the connective tissue to convert to gelatin, and
then about an hour more for all of it to convert. Continue
cooking past that point, however, and the gelatin itself starts
breaking down, losing its thickening power. So the ideal
chicken stock should be simmered for around 4 hours.
Luckily, chicken collagen isn’t the only place where you
can find gelatin. In fact, it’s sitting right there in the
supermarket: