Why do we have to be more careful about cooking temperatures in ground meat than in steaks and roasts?
Contaminants, such as the especially dangerous E. coli 0157:H7 bacteria, can multiply on the surfaces of larger, intact pieces of meat. When the meat, such as beef, is ground, those bacteria are dispersed into the mixture, where they can spread. The difference is that with a steak, you sear it on both sides of the grill, or in a pan, and theoretically, the bacteria are more likely to be killed. With ground meat, if it's not cooked thoroughly, the bacteria that have been distributed into the interior of the product won't be destroyed just by surface cooking.
Why should we concern ourselves about these issues? If you look at the news, you will notice more and more meat recalls by large companies. The meat is recalled, usually, because E. coli, or other contaminants, have spread and been identified as a cause of illnesses.
On June 24, a Greeley, Colo.-based meat company, JBS-Swift Beef Co., voluntarily recalled about 380,000 pounds of beef products, according to a report by the Reuters news agency.
That number was expanded over the weekend to reach about 421,000 pounds, according to the U.S. Department of Agriculture. Some of the meat, according to a spokesman for JBS-Swift, might have been contaminated when processed by other companies after the meat was distributed, according to Reuters.
In some cases, people die from a virulent strain of food contamination, though in the outbreak mentioned above there have been no deaths reported. But the very young, very old and people with compromised immune systems, should be extra careful that they eat well-cooked meat -- especially if it is ground.