Why Can Steaks Be Cooked Medium-Rare, But Hamburgers Must Be Cooked Throughly?
E.coli is only present on the outside surfaces of meat, which is why it’s acceptable to serve a medium-rare steak. Cooking the outside kills the pathogens, so the inside can be served pink. On the other hand, hamburgers must be cooked thoroughly. This is because the process of grinding mixes the E.coli from the surface throughout the meat.
During the cutting and wrapping of meat, the meat may come in contact with bacteria that is on the butcher’s knife, counter, hands of the handler or anything that touches. We can help to prevent this by keeping all surfaces clean and sanitized, but even then it is hard to completely prevent.
With a steak or solid piece of meat such as a roast, the bacteria will only be on the outside. They cannot chew their way through a cut of meat so they cannot get inside a roast or steak unless we let them hitchhike on a fork, knife, thermometer or grinder. Cooking or grilling the surface of the meat until well done, will kill the bacteria that may be there. If we are careful, there won’t be any bacteria on the inside and so it is okay to cook the inside to less than well-done temperature.
With ground beef, the grinder will spread bacteria from the outside to the inside of the meat. It is especially hazardeous because of the many, many surface in the ground meat, each of which may carry bacteria. That is why ground beef must be thoroughly cooked all the way through to the centre to a temperature that will kill the bacteria, which is 170’F (77’C). Because patties are too thin to accurately measure them with a thermometer, they should be cooked until the juices run clear. Cut them open to see inside. If they are still pink, they need to be cooked longer.