That steak may look juicy, but harmful bacteria could be swimming inside if you ignore cooking temperature.

RODALE NEWS, EMMAUS, PA—Don’t think you’re a dork if you walk around with a meat thermometer. “It’s cool!” says Bradley Marks, PhD, professor of biosystems engineering at Michigan State University in East Lansing. Of course, he’s a food-safety expert and knows all about the nasty bacteria that can lurk in meat—particularly Salmonella. Even whole cuts of meat aren’t safe from it, as was once thought. A 2008 study published in the Journal of Food Science, he and colleagues found that whole cuts of meat, such as steak, can be contaminated internally with Salmonella. And it’s harder to kill with heat when compared to ground meat. Medium-rare lover? You better read on.

THE DETAILS: Researchers sampled ground and whole cut pieces of beef from the same original lot and contaminated it with Salmonella, a type of bacteria found in the digestive tracts of humans and animals. Because it lives in animals, the bacterium can contaminate the meat during the slaughtering process, explains Marks. Workers who don’t wash their hands, or use contaminated surfaces, can also spread the bacteria. When people eat food contaminated with Salmonella, they develop fever, abdominal cramps, and diarrhea, which can last for up to a week. Victims usually recover without treatment, though a person with a weak immune system can develop more serious problems. The interior portions of whole cuts of beef like steaks or roasts have long been assumed to be sterile, but contamination and survival of pathogens have been reported. This study found Salmonella hiding deep inside whole cuts of meat.