Most hamburgers served in restaurants are served well-done, with the meat thoroughly brown, but some hamburger lovers prefer their burgers a little pinker and juicier. A medium-well hamburger is almost as fully cooked as its well-done counterpart, but retains a moister, pinker center. The difference between a medium-well hamburger and a well-done one can be tricky to judge.
The level of doneness in a hamburger is based on the appearance of its center. The center of a medium-well done hamburger is warm to the touch and has little to no pink meat. It will not be as thoroughly grayish-brown as a well-done burger, but the pink at the center should only be a slight tinge as opposed to the pink center of a medium burger.
Although the appearance of the center tells cooks how done a hamburger is, it can be difficult to tell from the appearance of the exterior. The most reliable way to test how done a hamburger is is to use a meat thermometer. The interior temperature of a medium-well done hamburger should be around 150 to 155 degrees Fahrenheit. Cooking a medium-well done hamburger on a grill should take about four and a half minutes per side. Cooking times can vary depending on the heat of the grill.
Meat must be cooked in order to kill harmful bacteria. Bacteria are found on the parts of the meat that have been exposed to the air. That's why it is safe to sear the exterior of a steak or similar cut of meat, leaving the interior relatively uncooked, but even the interior of a ground-meat patty has been exposed to the air. As a result, the Food Safety Information Service of the U.S. Department of Agriculture recommends that all ground meat be cooked to 160 F. The USDA considers only well-done hamburgers safe to eat.
Despite the USDA's warning and similar health precautions in other countries, some restaurant owners and food writers have pushed back against what they perceive as a prejudice in favor of well-done hamburgers. They argue that publicized cases of bacterial infection result from poor quality control in mass-produced frozen hamburgers, and that hamburgers cooked at lower temperatures can be safe if ground and cooked in sanitary conditions.