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 STATEBut 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. They include Colby, Monterey Jack, Muenster, Swiss, low-moisture mozzarella and provolone.CLICK HERE FOR MORE LIFESTYLE NEWSThat doesn't mean aged cheese is off the table, however. Mode said it can and should be included as part of a cheeseburger, just incorporated differently. CDR's own research chef is a fan of a smoked blue cheese or Brie with a burger, she noted."You could shred those cheeses or crumble those cheeses on your burger," Mode said. "Or you could even put them inside the burger patty for one of those Juicy Lucy burgers."American cheese is a favorite because it melts the same way nearly every time."American cheese is a processed cheese," Mode explained. "You start with a natural cheese, like a cheddar, and you shred it or grind it, and then you cook it along with an emulsifying salt."Cheese is essentially protein, fat and water, and the latter two "don't want to mix together," Mode said. The emulsifier binds the components together and leads to a smooth, complete melt.TEST YOURSELF WITH OUR LATEST LIFESTYLE QUIZMode herself grew up on a fifth-generation dairy farm, and CDR is dairy farmer-funded and serves cheesemakers across an 11-state region.She encourages people to try new cheeses with their burgers and pointed to a new "natural American cheese" with no emulsifying salt recently introduced by a Wisconsin cheesemaker."They changed the cheesemaking recipe — the way they make the cheese, so that it has the same or similar functionality to an American processed cheese while it still is a natural cheese," Mode said. "So there's that out there, too, for folks [who] are looking for a cleaner label."CLICK HERE TO SIGN UP FOR OUR LIFESTYLE NEWSLETTERMode is also enthusiastic about flavored cheeses that contain a little spice, herbs or smoke. She also recommends people consider cold pack cheese, the spreadable kind usually reserved for crackers."It's great to spread on your burger bun, especially if you toasted the bun so it's a little warm," she said.As far as when and how to apply cheese for a perfect melt, Mode said to do it at the very end."The burger is finished cooking, and usually at the end you let it rest a little, and that's the perfect time to add the cheese," she said. "If it's one that takes a little more oomph to melt, like a nice thick piece of cheddar, you can put a cover on it, and it'll hold that heat in."