Which is safer in terms of possible contamination: preground meat from the supermarket or meat ground at home?
Regardless of where the meat is processed, ground pork, poultry, and beef are safe to eat as long as they are cooked to 160 degrees—the temperature at which potential pathogens are inactivated. But since ground beef is frequently served at temperatures lower than 160 degrees, foodborne illness can be an issue. Meat-processing plants have stringent guidelines intended to prevent cross-contamination, but anyone who reads the news knows that outbreaks of salmonella and the harmful 0157:H7 strain of E. coli routinely occur.
However, only ground beef—not whole cuts—is considered risky. This is because contaminants do not penetrate the surface of a steak or a roast, and any that may be present on the surface will be killed during cooking, making the meat safe even if the interior is served rare. The risk occurs during grinding, when the exterior of the meat is distributed into the interior, taking any potential pathogens along with it.
As long as you follow safe-food-handling guidelines—including frequent and thorough hand washing, thorough cleaning of surfaces, and storing meat below 40 degrees—we believe that grinding beef at home is safer than buying ground beef at the store. Here’s why: The chance of a single cut of beef (that you then grind at home) being contaminated is relatively slim. Conversely, a single portion of preground beef can be an amalgam of various grades of meat from different parts of many different cattle. In fact, when we consulted Robert V. Tauxe, deputy director of the Division of Foodborne, Waterborne and Environmental Diseases at the National Center for Emerging and Zoonotic Infectious Diseases, he estimated that a typical hamburger may contain meat from hundreds of different animals. And obviously, the more cattle that go into your burger the greater the odds of contamination.
THE BOTTOM LINE: The only way to be absolutely certain that ground beef is free from harmful bacteria is to cook it to 160 degrees.