April 12th is National Grilled Cheese Sandwich Day. Learn how to make the perfect grilled cheese sandwich, and wash it all down with a little science, a few facts, and some history for dessert.

By Lola Gayle, Editor-at-large

National Grilled Cheese Sandwich Day, although mysterious in origins, is the perfect day to sink your teeth into a warm, gooey sandwich — with a little bit of science on the side.

What’s not mysterious is the origin of the sandwich itself. According to National Day Calendar, food historians claim that cooked bread and cheese is actually an ancient food, enjoyed across the world in many cultures. However, the modern version of the grilled cheese sandwich in the U.S. originated in the 1920s when inexpensive sliced bread and American cheese became easily available. More history here.

Chemistry of Cheese

Thanks to the American Chemical Society’s Reactions team, the video below is a “chemical ode to one of the finest comfort foods ever created.” Not only are they diving into the chemistry of cheese, they’re also offering some scientific advice on how to optimize your ingredients for the perfect grilled cheese experience.

You certainly can’t begin a grilled cheese sandwich without the perfect cheese. Bread is bread, but cheese? Now that’s where the magic happens!

There are a lot of cheeses to choose from, but for the perfect grilled cheese you definitely want one that will come out nice and stretchy. But what’s up with cheese to begin with? And how is it made? Let’s take a look, shall we?

According to the video, the first step to cheese-making is to form curds out of milk. Milk is 90 percent water, as well as a mix of casein and whey proteins, lactose, calcium, and fats.

Casein proteins float around in milk in molecular clumps called micelles. Micelles refuse to stick together because they have the same charge on the outside. These micelles hold around two-thirds of the calcium in milk, and calcium is the key to a perfect grilled cheese. The more the merrier!

To form curds, bacteria and enzymes are added to milk to make it coagulate. The bacteria convert lactose into lactic acid. This drops the pH which eliminates the charge of the casein micelles to help them stick together. Enzymes called rennet are also used to help speed things up a bit.

Once the curds are formed, the whey and excess moisture are drained. The little clumps are then heated, bathed in saltwater, and pressed together to make different types of cheeses.

Once pressed, the aging process begins. Some are aged for days, some for years. It all depends on the style of cheese being made. The longer it sits, the more lactose is converted to lactic acid, thus lowering the pH even further, making for a sharper cheese.

In the case of grilled cheese, that pH level has a huge effect on the calcium found inside and its texture when heated. If protein is the structural backbone of cheese, then calcium is the rebar that enforces that backbone. It’s what grips all the casein molecules together to form the micelles.

Melty, stretchy cheeses have casein proteins that can break away and “go with the flow.” And what that takes is a lower pH. This gives the calcium a break from holding the casein together, meaning more proteins break out of their cages to interact with the fats and moisture in the cheese. This makes everything flow together as one big, gooey mess.

If the pH is too low, the cheese will release all its oils when heated. That can leave you with a nasty, curdled, clumpy disaster.

The secret to getting the perfect cheese for your sandwich is to find one with the right pH to balance out the calcium and protein structures. That means the best cheeses are those with a pH level somewhere between 5.3 and 5.5. Some prime examples are manchego, gruyere, and gouda.

Tips from the Pros

If you can’t decide between sharp or mild, I suggest you start with mild. That’s because milder cheeses will give you the exact texture you’re looking for.

But what about processed American cheese? According to the video, this type of cheese is made by melting together two different types of cheese — such as colby and cheddar — and adding an emulsifier like sodium or potassium phosphate. This limits the amount of calcium holding everything together, all the while increasing the pH. This makes for a highly-meltable cheese product with a lovely and mild flavor.

But Why is Cheese So Darned Addicting?

Well, according to a University of Michigan study, cheese is addictive because not only is it highly processed and fatty in many cases, it’s actually the casein proteins that keep us coming back for more (and more…and more…and more).

According to the Los Angeles Times, when we digest casein it releases opiates called casomorphins, which essentially trigger happy dopamine receptors in a similar way to drugs.

It’s certainly debatable just how much of an opioid effect casomorphins actually have after milk is processed into cheese. However, one only has to scan the dairy aisle in your favorite grocery store to see that Americans can’t seem to get enough of the stuff.

I know I would much rather go on a cheese bender than consume illicit drugs!

Fast Facts About Cheese

  • There are around 2,000 varieties of cheeses. Visit Cheese.com for a large list of types.
  • The most popular cheese recipe is the United States is “macaroni and cheese.” But who cares about that when there’s grilled cheese sandwiches to be had?!
  • Cheese-making has been around for nearly 4,000 years, according to the International Dairy Foods Association. Though no one really knows who made the very first cheese, historical records indicate that travelers from Asia brought their technique of cheese-making to Europe before the Roman Empire.
  • United States government cookbooks describe Navy cooks broiling “American cheese filling sandwiches” during World War II.

Cheesy Quotes

“The clever cat eats cheese and breathes down rat holes with baited breath.” – W.C. Fields

“Wine and cheese are ageless companions, like aspirin and aches, or June and moon, or good people and noble ventures.” – M.F.K. Fisher

“A corpse is meat gone bad. Well, and what’s cheese? Corpse of milk.” – James Joyce

“Age is not important unless you’re a cheese.” – Helen Hayes

“Cheese is milk’s leap toward immortality.” – Cliff Fadiman

“Cheesemakers are ‘Managers of Rot’.” – Michael Pollan

So there you have it. Now go make me a sandwich!