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Burger recipes and cooking tips from J. Kenji López-Alt.

The Burger Lab: Cheese Sauce for Burgers, Fries, and Chips

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[Photographs: J. Kenji Lopez-Alt}

My wife, in case you haven't noticed, is an odd sort of bird. For starters, simply getting married to me was a questionable act; I don't have all that much to offer. I've got barely any money. My slim figure and good looks left me long ago (right about the same time as the 500th hamburger). I steal the covers when I sleep. I forget to put the toilet seat down (that's if I even remember to flush it in the first place).

What I can promise her, on the other hand, is that if there is any food in the world she desires, I will not rest until she is inundated in mountains of it. And what, you may ask, does my fair wife wish to be drowned in? Foie gras? Truffles? Links and links of natural casing Sabrett's hot dogs?

Nope. Just one thing: cheese sauce. The ooey, gooey, velvety smooth, shiny, silky, hot, tangy, and salty goo that chain restaurants and movie theaters ooze over their fries, hot dogs, and nachos.

According to her, the gold standard for this liquid gold is from the pumps in the fixin's station at the fast-casual burger chain Fuddruckers. We hit the nearest location in Paramus, New Jersey, for a taste test.

Straight out of the pump, it's some really miraculous stuff: it flows like magma, with a silken sheen and not a hint of graininess.

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One of the true tests of cheese sauce is how it reacts after it cools down a bit. I let one cup of the Fudd's sauce sit on the table while we enjoyed our burgers (their burgers are shockingly good), then retested for consistency by pouring it over my fries.

Still gooey, still creamy, still shiny—a stark contrast to the plastic-like cheese sauce they serve at Shake Shack (surely their poorest offering).

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Taste-wise, on the other hand, it leaves more than a little something to be desired. It starts off salty and tangy in a way that can only be described as "piquant" (I've never used that word in my life), but from there goes downhill with an acrid, chemical finish.

My goal: to create a cheese sauce with the melty, gooey, spreadable dippability of Fuddruckers sauce, but with the complex flavor of real cheese. My path there wasn't exactly smooth sailing.

Gimme a Break!

Cheese melts, right? So why not just throw some real cheddar cheese in a bowl, and heat it until it's at perfect sauce consistency?

Well here's why:

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Not pretty, right?

In order to explain why that happens, let's take a closer look at exactly what cheese is made of:

  • Water is present to varying degrees. Young cheese like Jack, young cheddars, or mozzarella have a relatively high water content—up to 80 percent. The longer a cheese is aged for, the more moisture it loses, and the harder it becomes. Famous hard cheese, like Parmigiano-Reggiano or Pecorino Romano may be as little as 30 percent water after several years of aging.
  • Milk Fat In solid cheese is suspended in the form of microscopic globules kept suspended in a tight matrix of protein micelles (more on those in a second). Under around 90°F, this fat is solid. Because of this, and because of their suspension, they don't come into contact with each other to form larger globules: cheeses stay creamy or crumbly, instead of greasy.
  • Protein micelles are spherical bundles of milk proteins. Individual milk proteins (the main ones are four similar molecules called caseins) resemble little tadpoles (or sperm, if you will), with hydrophobic (water avoiding) heads, and hydrophillic (water seeking) tails. These proteins come together head first in bundles of several thousand, protecting their hydrophobic heads, and exposing their hydrophillic tails. These micelles link together into long chains, forming a matrix that gives the cheese structure.
  • Salt and other flavorings make up the rest of the cheese. Salt can have a profound effect on the texture of the cheese—saltier cheeses have had more moisture drawn out of the curd before being pressed, so tend to be drier and firmer. Other flavorful compounds present in cheese are mostly intentional byproducts of bacteria and aging.

Anyone whose ever tried to make an aged cheese can tell you that it's all about delicately balancing ingredients ratios, timing, and temperature. Heat throws this whole balance off. To explain how, let me quote a little from McGee's On Food and Cooking:

First, at around 90°F, the milk fat melts, which makes the cheese more supple, and often brings little beads of melted fat to the surface. Then at higher temperatures—[around 150°F for Cheddar]—enough of the proteins holding the casein proteins together are broken that the protein matrix collapses.

At this point, you'll notice two things happening. First, the liquefied fat will come together into greasy pools and separate from the water and proteins. As you continue to stir the melted cheese, the proteins—which are suspended in whatever part of the water hasn't yet evaporated—glue themselves together with the help of calcium into long, tangled strands, forming the stretchy curds that anyone who's eaten string cheese is familiar with.

To get a cheesy sauce that's shiny and smooth, and not greasy nor stringy, the key is to discover a way in which to keep the fat globules from separating out and pooling, adding moisture to thin the texture out a bit, and figuring out a way to keep the proteins from breaking apart and rejoining into long strands.

Well, how the heck do you do that? Luckily for us (and allow me to quote Peter Pan here for a moment): All of this has happened before, and it will all happen again.

Getting Saucy

For clues on how to keep cheese melty, I turned towards Kraft's Velveeta—the undisputed king of creamy goo*.

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A close look at their ingredients list reveals a couple of clues. First of all, milk and water play a large part in its makeup, indicating that its moisture content is higher than that of straight cheese. Extra protein is also in there, in the form of milk protein concentrate. Finally, it contains sodium alginate, a natural gum extracted from algae.

I know that sodium alginate, by thickening the liquid in the cheese, acts to prevent fat globules from coalescing, and individual proteins from sticking together too easily. It also increases the viscosity of the water, adding body to the sauce. But what about the extra milk proteins? Well, it's well known that cheese that have a higher protein-to-fat ratio are much better at melting. Low fat, high moisture, high protein mozzarella, for example, turns into a stretchy goo with almost no help at all—you have to heat it significantly before its fat separates out. Cheddar, on the other hand, has an especially high fat ratio. It'll turn greasy if you look at it wrong.

So where does one go about finding excess milk proteins and gums? Turns out that there's a couple of sources already present in most homes:

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Cream cheese is a fresh cheese product with a relatively high fat content kept stable with the addition of guar and carob gums. Although it's high fat, my thought was that adding it to my melted cheddar would provide enough stabilizing gums to keep the cheddar itself from separating. Evaporated milk is essentially milk with much of its water content removed, effectively giving you a very concentrated source of milk proteins. Hopefully these extra proteins would help stabilize my sauce as well. Finally, mayonnaise contains neither milk proteins nor thickeners, but it's got plenty of lecithin, an emulsifier naturally present in egg yolks. The lecithin acts as a sort of liaison between the milk fats and the liquid, keeping them in relatively stable harmony.

I made a few more batches of cheese sauce, one with cream cheese added, one with evaporated milk, and one with mayonnaise, adjusting the consistency as needed with a bit of whole milk (the evaporated milk version didn't need any extra milk). As a control, I also made one sauce melting the cheese in just plain milk, as well as one sauce which I made mornay-style: first forming a flour, butter, and milk bechamel then adding my cheese to it.

Of the five sauces, the milk version was a total bust:

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Not quite as greasy as straight up cheese, but the cheese proteins still seized up and locked together into a stringy, gloppy, inedible mess.

The bechamel-based sauce also had the same problem that bechamel sauces always have: No matter how well they are made, there is still a faint graininess to them and a distinct flavor that may be appropriate in a lasagna or a Hot Brown Sandwich, but not for fry-cheese.

The other three fared much better:

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Each one managed to come together into a relatively smooth, glossy sauce, though none of them were quite as smooth as I'd like them to be—you still noticed a distinct protein clumps. The mayonnaise-based sauce also tasted, well, like mayonnaise.

It was down to the cream cheese or evaporated milk. Allowing them to cool worsened the problems. Both sauces completely lost their flow structure, instead turning grainy and broken, like semi-dry concrete.

I needed a better way to keep the fat, protein, and water together. I'd already tried through various chemical methods (extra proteins, adding emulsifiers), but what about a mechanical means?

Starches have no chemical effect on the way sauces come together, but can help hold emulsions more stable through different means. First, they absorb water and expand, thickening the liquid phase of the sauce (the same way gums do). But more importantly, starches are like the bouncers of the sauce world: They're bulky, and physically impede proteins and fats from coming together and coalescing.

I'd already tried flour (in the form of the bechamel) with no success, but what about a purer starch like cornstarch? That was the boost my sauce needed. This time, even when allowed to cool completely, the sauce stayed silky, glossy, and dippably good.

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In the end I decided to stick with the evaporated milk, as it allowed for more flavor control (to get the cream cheese to work, I had to add a significant amount of it, which ended up lending its own distinct flavor to the sauce). I found that the easiest way to incorporate the corn starch was to simply toss it with the grated cheese. That way, when I added the cheese to the pot, the cornstarch was already dispersed enough that it couldn't form annoying clumps.

As far as flavor goes, using an extra-sharp cheddar along with a little dash of Frank's Red Hot gave it that distinct piquancy (there's that word again). Also, if you're the kind of person who likes to add salsa to Velveeta and call it "con queso" dip, you may have just found a new best friend.

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Want a food lab triple whammy? Just pair this sauce up with our Perfect Thin and Crispy French Fries and Chili for Chili Fries. Snack time will never be the same.

*[Insert dirty Ron Jeremy joke here]

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