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Few dishes get to carry the title of comfort food classic. Creamy, delicious homemade mac and cheese tops that exclusive list. It has the ability to warm up a cold day and instantly connect us with childhood memories.

But behind all that warm fuzziness is a series of intricate chemical reactions that happen when the right ingredients are brought together with careful attention to culinary technique. Once you understand these reactions and master these techniques, you can deploy them to create the dish of your dreams, every time.

A little science will ensure you never make clumpy, bland, flabby, or oily macaroni and cheese again. Here is what you need to know.

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Starch does two jobs in one

The chemistry that makes mac and cheese so good starts with the first two ingredients that go into the pan. Flour and butter are cooked together to make roux, a hard-working mixture that is the foundation of the dish's cheese sauce.

As the two ingredients cook, melted butter surrounds flour particles, keeping them from clumping together when liquid is added. When hot milk is whisked into the roux, granules (or little sacs) that hold the flour's starch absorb the liquid and break open. Long, unwieldy starch molecules are released and become entangled, trapping the milk and thickening the sauce. These starch molecules also act as built-in insurance, preventing clumping as cheese is melted into the mixture.

Great flavor, reluctant melter

To get a sauce with creamy texture and distinctive flavor, you need more than one type of cheese. That's because cheeses that have a smooth, flowing, cohesive melt often have subtle flavor that is lost in the hearty dish. Cheeses with well-developed flavor, on the other hand, tend to break into unseemly, rubbery clumps and pools of separated oil when heated.

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The structure of cheese is what determines how well it melts. What gives cheese structure are clusters of the milk protein casein, which form a web that entraps fat and moisture. Cheese with a loose, flexible web melts smoothly as bonds between proteins gradually break. Cheese with tighter protein networks, or networks that are fragmented, are more difficult to melt or tend to separate. How long a cheese has matured, its acidity, the amount of fat and moisture it contains, and how it was made all have an impact on its structure.

In general, young, high-moisture cheeses — like Monterey Jack and Gruyere — are consistently good melters, while cheeses like aged cheddar that have more-complex, well-developed flavor are less-reliable melters. For the best results, combine cheeses of both types.

Cheese doesn't like to be rushed

When cheese is subject to too much heat too soon, an otherwise good sauce can end up with lumps. Taking the pan off the burner, then gradually adding room-temperature, shredded cheese while gently stirring gives the cheese its best chance for a smooth melt.

Once the cheese is in the pan, the same starch molecules that thicken the sauce prevent it from breaking. When a cheese separates into clumps and oil, it is because the bonds between protein molecules that have broken on melting rejoin, squeezing out fat globules, which then pool. Long starch molecules prevent clumping by physically getting in the way so proteins cannot get back together and fat globules cannot coalesce.

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Pasta needs attention, too

When it comes to making the dish right, the chemistry of the mac matters as much as the chemistry of the cheese. Elbow macaroni has the perfect balance of firm yet tender texture after cooking because it is made from high-protein semolina flour. Dried pasta made with semolina flour consists of starch granules suspended in a strong protein network. On boiling, the protein network expands and starch granules absorb water and burst open, releasing starch molecules. This happens on the pasta's surface first, where the concentrated, glue-like starch can cause the pasta to stick together (a quick stir disperses the excess starch into the boiling water).

Undercooking pasta by about one minute before adding it to the cheese sauce will keep it from becoming too soft when the dish is baked. A quick rinse with cold water stops the cooking once it is drained. The short length and curved, hollow shape of the macaroni are perfectly suited to the substantial cheese sauce that coats and fills the pasta as it bakes. Sauce clings best to pasta with a coarse, grooved surface.

In the oven, the smooth, flavorful, stabilized sauce bubbles deliciously, pasta sets to just the right texture, and a topping of buttery breadcrumbs crisps and develops flavor, adding crunchy contrast to the creamy dish.

What you get when you pull it from the oven says it all. Mac and cheese has earned its place at the top, with a little help from science.


Valerie Ryan can be reached at valerie.ryan.j@gmail.com.

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