why does pan searing meat make it tough after a long time on the pan, but simmering makes meat more tender the longer its done?

Question

why does pan searing meat make it tough after a long time on the pan, but simmering makes meat more tender the longer its done?

In: Chemistry

Answer 1

Initial application of (high) heat causes proteins to “tighten up”. So this can drive water out of the meat and render it tough and fibrous. So the meat needs to be sliced thin against the fibers to keep it less tough (stir fries etc) or cooked quickly and not be allowed to get too tough to eat (rare to medium rare steaks for example).

Simmering will still cause some of this to occur but slower. However over a longer period (45mins to hours), things like fats and connective tissue in the meat render out and release into the meat causing it to get less tough. And of course simmering means high humidity and liquids which help the meat to not get too dry. Proteins in the meat start to break down as well.