Physicists have discovered the perfect recipe for a popular pasta dish.

Some dishes may seem deceptively simple in description. Cacio e pepe pasta consists of just four ingredients: spaghetti, hard Pecorino Romano cheese, freshly ground black pepper, and water. However, achieving the perfect, silky texture from these ingredients requires chefs to have a deep understanding of chemical and physical processes, along with experience and intuition.

Physicists from Germany, Spain, Italy, and Austria have thoroughly examined what is needed from both the ingredients and the chef to create the perfect pasta. It turns out that the properties of the pasta are critical, while the texture of the sauce can be relatively easily adjusted.

The scientific paper is published on the arXiv website and is freely accessible. The researchers claim that after reading this article, anyone will be able to make a good cacio e pepe pasta.

The basic process is straightforward. Spaghetti should be cooked in salted water until al dente, removed from the water, transferred to a pan, and mixed with cheese, pepper, and pasta water. The result should be a fragrant, nourishing, and slightly spicy pasta in a homogeneous silky sauce.

A common issue when preparing cacio e pepe is the "mozzarella phase," where the sauce breaks down. The cheese does not create an emulsion with the water, instead, it tends to clump together. To prevent this, the chef must guess how much pasta water to use and how long to cook the pasta before mixing the ingredients, as this affects the amount of starch in the water.

The scientists recorded the temperature of the water, the amount of cheese, and the starch content in the water to find the ideal ratio of ingredients. They photographed each variation for a visual assessment of the sauce's state.

The researchers discovered a clear relationship between the temperature of the liquid and the amount of protein from the cheese in it. The phase diagram of the sauce indicated that temperatures above 60 degrees Celsius make the sauce highly sensitive to the amount of protein. At temperatures above 80 degrees, achieving a homogeneous sauce becomes extremely challenging.

The physicists concluded that the amount of starch in the pasta water determines the state of the sauce. Spaghetti that releases too little starch during cooking creates solutions that tend to cause proteins to clump together. In contrast, the starch released into the water during cooking wraps around the proteins from the cheese and pasta, preventing them from forming clumps.

The study's authors developed a model that describes the phase diagram of the sauce, which aligned well with experimental data. They had to consider the interactions between water, starch, and two types of proteins—wheat protein from the pasta and milk protein, casein, from the cheese. The protein content in the solution also significantly affects the state of the sauce, but regulating the amount of starch is much simpler, so the researchers suggested focusing on this ingredient to create the perfect sauce.

Here’s the recipe for ideal cacio e pepe pasta from the physicists for two servings. You will need:

• 240 grams of pasta (spaghetti, tonnarelli, or rigatoni)
• 160 grams of grated Pecorino Romano cheese (up to 50 grams can be substituted with Parmesan)
• four grams of potato starch
• black pepper
• salt

1. In boiling, well-salted water, cook the pasta until it reaches al dente; the cooking time is usually indicated on the packaging. Stir the pasta for the first couple of minutes.
2. Dissolve the starch in 40 milliliters of water and heat it slowly, possibly using a water bath. The solution should become clear and slightly viscous from cloudy—this indicates that the starch has absorbed the water. Let the solution cool for a few minutes.
3. Combine the cheese and starch solution. It’s best to blend them until completely homogeneous. Add water if the mixture is too dry.
4. Add freshly ground black pepper to the mixture of water, starch, and cheese. Start with half a teaspoon, increasing the amount to taste.
5. Reserve about 200 milliliters of pasta water, drain the rest, and cool the pasta for about a minute.
6. Mix the pasta with the cheese-starch mixture. If the sauce is too thick, gradually add the reserved water, about one to two tablespoons at a time, stirring thoroughly each time.