The best cheese for a burger, according to expert — and why some popular picks fall flat

It's National Cheeseburger Day , but while Americans may agree that cheese makes a burger better, deciding which cheese belongs on top is another matter.

A 2015 YouGov/HuffPost survey of 1,000 U.S. adults found that 71% preferred cheeseburgers, compared with just 20% who preferred hamburgers.

American was the top choice among cheeseburger fans, with 40% choosing it, followed by cheddar at 31%.

Swiss cheese earned 10% of the vote, while provolone garnered 5% and blue and Jack both received 4% each.

AMERICA'S BEST FAST-FOOD BURGER REVEALED — AND IT’S NOT AVAILABLE IN EVERY STATE But choosing the right cheese isn't just a matter of taste.

How a cheese melts — and whether it stays put on the burger — comes down to science.

"A classic cheeseburger, what I think of is that orange slice, which is usually an American cheese or cheddar cheese," Gina Mode, coordinator of the Cheese Industry and Applications Group at the Center for Dairy Research (CDR) in Madison, Wisconsin, told Fox News Digital.

The slice has to do three things at once, she said: taste like something, melt well and stay put.

"You want it to have that nice cheese flavor, that cheddar flavor," Mode said.

"You want it to have a nice softness to it when it melts, and you also don't want it to flow off your burger." A good melt comes down to a few scientific variables, Mode explained.

The cheese needs to have the right composition, the right pH and the right amount of intact casein, which is the milk protein .

As cheese ages, that structure changes, building flavor but working against meltability.

"You'll notice an older cheddar is going to crumble, and it's probably going to oil off if you melt it," Mode said.

Young, natural cheeses that hold their structure are safe bets for a burger .