For a while, we've been hearing about how McDonald's plans to grow by doing things like getting people to think of it as a place for chicken and launching all-day breakfast.

But last night, the world's second-largest restaurant chain announced a key change to its burgers that's probably more fundamental to its original business model.

The switch, which McDonald's had first discussed last year, is that it will now be making two of its burgers on its menu using fresh beef rather than frozen.

About 3,500 McDonald's locations will use fresh meat immediately, and the rest will make the switch in May. McDonald's has been testing the fresh burger idea in select restaurants in Texas and Oklahoma for about 18 months, the company said.

The whole challenge, especially for a chain at the scale of McDonald's, has been to achieve consistency and speed, said Chris Kempczinski, McDonald's USA president, according to the Chicago Tribune:

McDonald's is known for speed and convenience. What we had to figure out is how do you cook only when someone orders it, but do it in a way that doesn't impact service times. When people come to McDonald's, they're not going to wait five minutes for a burger.

For now at least, the change affects only two burgers: the Quarter Pounder and the Signature Crafted. The Big Mac and all other hamburgers on the menu--which frankly might be more subliminally associated with the chain to begin with--will still be prepared and "flash frozen" before being shipped to restaurants.

That "flash frozen" technique, you might recall, was what Wendy's mocked relentlessly in its Super Bowl ad earlier this year. I'd thought at the time that it was smart of McDonald's simply not to respond, as it seems to have done--but simply to move ahead with its plans. 

Wendy's is a big company, but it's dwarfed by McDonald's. In fact, when McDonald's shares dropped 4.8 percent last Friday--the worst day in the company's history--the single-day loss in value would have been enough to buy the entire Wendy's chain, theoretically, and have a lot of money left over.

That drop had in turn been prompted by an influential industry analyst's report that said the company's new "$1 $2 $3 Dollar Menu" was not only underperforming, but was also negatively affecting some of the restaurant's other campaigns.

But, as the Tribune pointed out, analyst David Palmer and his colleagues at RBC Capital Markets, who wrote the report, were more bullish on McDonald's future in the longer term, "in part because of the anticipated launch of fresh beef."

The official rollout was just announced last night at a media event at a McDonald's in Oak Park, Illinois, so we'll have to wait to see how people respond. But on Twitter, there were some amused reactions, suggesting that for normal customers, the whole fresh versus frozen debate isn't even something they were really aware of.

People suggested they don't necessarily want to get into the details of fast food business models. They choose a go-to fast food restaurant for taste or convenience or habit, it seems--but without necessarily unpacking the whole question of what makes a burger at one place taste different from one at another.

Or--and ironically, I suspect this is the case for a majority of reporters and columnists writing about this today--they don't eat fast food at big chains very much anyway.