Meats with a low fat content, like shrimp and chicken breast are often suggested to be cooked at a high temperature for a short period of time.
However meats with a higher fat content, such as beef brisket and pork ribs, are often to suggested to be cooked low and slow.
Oil has a lower specific heat than water which means it heats up faster.
Given this, I would expect high fat meats to have shorter cook times.
Why is it the reverse?
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the fat insulates the deep insides from the heat, so heat takes longer to reach the middle than on watery lean cuts, since water is a great conductor of heat. Also the bones of ribs are a heat sink, and brisket has all sorts of weird substances you need to melt away.– dandavisAug 19, 2021 at 22:57
2 Answers
The cuts you are talking abut don't just have fat, they have collagen. Collagen requires long cooking in order to be converted to gelatin and stop the meat being tough and chewy, and to add that delicious richness to the cooking liquor and succulence to the meat.
Because cooking time has nothing whatsoever to do with the specific heat of the food. It's determined by what you want the result of cooking to be.
High-fat meats (like pork and beef) can be cooked low and slow because the fat stays in the meat and keeps it moist over long cooking. Whereas low-fat meats (like chicken breast or seafood) primarily have water, which evaporates, making them extremely dry and unpalatable if cooked long in a dry environment.
Additionally, the "high-fat" meats are more likely to be cut into large, thick portions which are suitable for slow cooking. They don't have to be, though; consider both bacon and Mexican-style skirt steak, either of which is cut thin and then cooked "at a high temperature for a short period of time".
Plus, see spagirl's answer about collagen.