Overcooking chicken destroys the flavor and texture of the meat. The meat becomes tough because the fat, protein and sugar molecules get fused together. This makes the meat difficult to cut, chew and digest.
The best way to test if chicken is cooked is to use an instant-read thermometer to check the meat's internal temperature. To use an instant-read thermometer, pierce the meat in the thickest part without hitting the bone, because the bone is hotter than the meat. Chicken held at 148 degrees Fahrenheit destroys 99.99 percent of salmonella. At 160 degrees Fahrenheit, the proteins in the meat unfold, release their moisture and become dry.