I'm just thinking about roasting a chicken in the oven. The heat in the oven does work on the chicken to cook it, but is the same amount of energy dissipated from the oven as is put in, or is some energy stored in the cooked chicken. More broadly, does anyone know the details of the reaction taking place when raw meat is cooked? What about an egg?
Several reactions happen during cooking, both endothermic and exothermic. Proteins will undergo denaturation (unfolding), followed by hydration. Complex hydrocarbons may break up, and resulting simple sugars are typically also hydrated.
Such reactions are often very well balanced: energy required to unfold a protein is almost fully recovered when the protein is hydrated, and it's similar with hydrocarbons. Therefore, no significant amount of additional energy is retained in food after cooking.
What cooking increases is the amount of energy available to you. If you eat raw meat, your body will have to spend energy denaturating the proteins, and the energy of subsequent protein hydration will be lost as heat. Also, depending of the type of food, your body may not be able to digest it fully when it's raw. That's why you get more calories if you eat cooked food.
There are endothermic reactions but pretty sure cooking is not one of them. The energy (heat) is not retained in the food. Cooking breaks down the food. Mainly oxidation - burnt meat is charred like a burnt log.