McDonald's is considering a dramatic change to its burgers

McDonald's is expanding a test of its most dramatic menu change in decades: replacing frozen beef patties with fresh beef.

The fast-food chain is adding fresh, never-frozen beef patties to 328 restaurants in North Texas, following tests at 75 restaurants in Oklahoma and 14 restaurants in the Dallas-Forth Worth area, Instinet analyst Mark Kalinowksi revealed Thursday.

The fresh patties will be used in McDonald's Quarter Pounder burgers, which include the Quarter Pounder with cheese, the Double Quarter Pounder with cheese, the Quarter Pounder Deluxe, and the Bacon Clubhouse Burger.

"This collection of McDonald's restaurants... appears to mark the largest expansion to date of McDonald's US test of never-frozen beef," Kalinowski wrote in a note to clients. "We view this latest expansion of never-frozen beef for quarter-pound beef patties as another signal as to the direction McDonald's US is likely to head - more test markets/restaurants are likely to introduce never-frozen beef in coming months."

McDonald's rival Wendy's has long used its fresh beef as one of its main selling points.

Switching to fresh beef represents a massive challenge for McDonald's, but one that could potentially pay off through an improved public image and better-tasting burgers.

The company has long relied on an extensive network of suppliers who make, freeze, and ship beef patties to its more than 14,000 restaurants in the US.

Expanding the test would require a massive shake-up to that supply chain.

Some franchisees have warned that at the restaurant level, it would introduce a whole range of new food-safety issues.

"I have major concerns over food safety and our lack of ability to serve a large number of customers quickly," one franchisee wrote in response to a survey by Instinet analyst Mark Kalinowski in July.

The potential for foodborne illnesses is higher when uncooked meat is kept at a temperature above 40 degrees Fahrenheit, according to the USDA.

But other franchisees said the change could improve business.

"Faster cook times, juicier product, seared product versus stewed meat," one franchisee wrote.

Another said, "Many customers perceive unfrozen to be better for you. Perception is everything."