This image provided by McDonald’s Corporation shows a Quarter Pounder burger. McDonald's says it will swap frozen beef patties for fresh ones in its Quarter Pounder burgers by sometime in 2018 at most of its US locations. Employees will cook up the never-frozen beef on a grill when ordered. Courtesy of McDonald’s Corporation via AP

Washington - McDonald's announced a major change to the Quarter Pounder on Thursday: By next year, it will contain fresh - rather than frozen - beef patties.

The announcement comes after a year of pilot tests at locations in Dallas and Tulsa. The switch to fresh meat has been hyped as the chain's "most drastic menu change in decades." It comes in response to consumer demands for fresher ingredients - which has seen many turn to brands like Wendy's and Five Guys, which advertise the fact that their burgers are never frozen.

But while "fresh" may appeal to consumers, it also carries risks - risks made apparent in the infamous E. coli outbreak at Chipotle. When the investment firm Nomura surveyed 27 franchisees representing 200 McDonald's locations during fresh beef trials last summer, several expressed concerns about increasing the risk of foodborne illness by switching from frozen to fresh.

"If we do not handle the meat perfectly there is the opportunity for bacterial invasion of our product," one wrote.

"An uncaring employee [could do] something that puts the entire system at risk," said another.

Chains like McDonald's have traditionally minimized these risks through highly standardized, centralized systems that limit the number of people who can accidentally contaminate food or mishandle it in a way that leads to pathogen growth. Produce is chopped in central kitchens where it can be tested for microbes and -- crucially for McDonald's next big step -- burgers arrive frozen, a state which retards E. Coli growth. They are stored in freezers until the moment they go on the grill, and those grill tops will not release until the patty has been on the heat for a certain period.

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It is, as Donald Schaffner, an extension specialist in food science at Rutgers University, told the Post in January, a system that has "engineered human frailty out."

By switching to fresh patties, however, McDonald's is adding a small amount of human frailty back in. For safety reasons, fresh beef cannot contain even trace amounts of E. coli when it leaves the manufacturing facility, said Bill Marler, a food-safety lawyer who has been involved in litigation against McDonald's and several other restaurants.

Small risk

While freezing greatly slows E. coli growth, the bacteria multiply rapidly at room temperature. And at no point can the worker flipping your fresh burger leave it unrefrigerated.

"If I was them, I would ramp up the training for the people handling the food," Marler said. "They've got to keep it in the fridge. If you stack 30 patties out while you're cooking when it's 70 or 80 degrees in the kitchen, you're going to have bacteria growth. And that could be a problem."

Marler cautions, however, that the risk is very small - so small, in fact, that he's not worried. And that says a lot about the tremendous gains that chain restaurants and the beef industry have made when it comes to food safety.

The issue has been an industry priority since 1993, when a strain of E. coli found in Jack in the Box burgers killed six children and hospitalized more than 170, said Juelene Beck, a former vice president at Burger King, speaking to the Post in January. In the aftermath of that tragedy - which prompted a number of lawsuits and a national outcry - suppliers considerably beefed up their in-house testing practices, and chains like Donald's ramped up oversight.

"The beef industry has done a remarkable job putting me out of business," joked Marler, who has seen his burger-related cases dwindle to almost nothing.

As a result, E. coli contamination in restaurant-served beef is relatively rare today. Restaurants like Wendy's have developed complex supply chains and audit procedures to accommodate fresh beef. That may explain why McDonald's feels confident making the switch now, after several decades with frozen meat.

McDonald's isn't taking the plunge all at once. This switch applies only to the Quarter Pounder, meaning that the beef used in many of McDonald's other burgers, including the Big Mac, will still come frozen. So will many of the chain's other offerings, including fries and McNuggets.

When can we expect to see those products fried up fresh in stores?

McDonald's says only that it is "accelerat[ing] the pace of change around how we source and serve our food" - and that, cryptically, "we're just getting started."