The USDA researchers found considerable variation both between and within beef patty formulations in endpoint temperature and color, even when controlled cooking procedures were followed. Therefore, unless a food thermometer is used when cooking ground beef patties, it is difficult for consumers to determine whether the patties are thoroughly cooked. This phenomenon is primarily associated with the pH and the level of pigment in the meat, as well as the fat content. Normal fresh muscle has a pH ranging from 5.3 to 5.7. A high concentration of pigment also contributes to a red color in cooked meat.
Meat coming from bulls typically exhibits both a higher pH and high concentrations of pigment.
But when pH is held constant, the concentration of total pigment contributes to the abnormal internal color. Trimmings from many sources are combined. A third factor affecting cooked ground beef color is the amount of fat in beef patties. There is considerable variation both between and within beef patty formulations in endpoint temperature and color even when controlled cooking procedures are followed. Advice for Consumers To avoid foodborne illness, USDA recommends that meat and poultry be cooked thoroughly.