Higher temperatures recommended, cooking ground beef compared to steak
“While the idea of pink steak might sound good and is safe, the same is not true for a burger,” states Jeff LeJune, a professor in the College of Food, Agriculture and Environmental Sciences at The Ohio State University.
“When we put a piece of meat on the grill, the outside of the meat heats up and therefore can destroy the bacteria on the surface, but the interior takes a lot longer to heat up,” he explains.
The interior of a steak is relatively sterile and does not contain the same harmful bacteria that ground beef does.
“For a burger, the meat is put through a grinder and whatever is on the surface ends up in the interior, and the interior ends up on the surface. It’s all mixed up,” remarks JeJune, noting that the bacteria are introduced throughout the product.
To explore this concept, he conducted an experiment using two different kinds of growth media.
“The first one was a non-selective media that is very nutrient-rich and allows all kinds of different bacteria to grow on it. The second one contains bio-salts and other ingredients that would be present in the intestines. It selects for organisms that would grow in the intestine like coliforms and E. coli,” he says.
Samples were created using both mediums for interior and exterior cultures from raw steak and raw hamburger.
“We cooked the burgers and steak to 140 degrees, which would be medium rare. Then we cooked them to 160 degrees,” he notes.
Samples were taken from the interior and exterior of both the steak and hamburger at both temperature points and applied to the two types of growth media.
“We put our petri dishes in the incubator and left them overnight. Bacteria like warm temperatures, so that’s one reason we put our food in the refrigerator when we aren’t going to eat it right away,” LeJune comments.
After removing the samples from the incubator, LeJune and his team compared the samples heated to 140 degrees to look for bacterial growth. There was no bacterial growth from the internal samples of cooked steak, but growth colonies were visible on the samples from the ground beef.
“To make sure that the burger is adequately cooked, we should cook it to 160 degrees. At that temperature, we had no bacterial growth from either the steak or the burger,” he states.
The results of LeJune’s study showed that the surface of both raw steaks and raw burgers can be contaminated with bacteria, but only the raw ground beef was contaminated on the interior.
“As we cooked it, the numbers decreased, but even cooking to 140 degrees leaves bacteria on the inside of a ground burger,” he says.
He suggests using a meat thermometer to test the doneness of meats and cooking ground beef to a160 degrees to reduce the risk of foodborne illness.
“Don’t eat pink burgers,” LeJune remarks. “They are not safe.”
Natasha Wheeler is editor of the Wyoming Livestock Roundup and can be contacted at firstname.lastname@example.org.