Imagine the pasta-bilities

Perfect cacio e pepe

Cacio e pepe is the simplest of the four fundamental Roman pasta dishes—its only ingredients are pasta, starch-enriched pasta water, pecorino cheese, and black pepper—and yet, it is notoriously difficult to get right. Mix the wrong proportion of cheese and pasta water at the wrong temperature, and the casein and whey proteins will aggregate, resulting in a clumpy mess instead of a silky sauce.

Fortunately, a group of Italian researchers at the Max Planck Institute for the Physics of Complex Systems recently shared a scientific solution to stabilizing the sauce (ArXiv 2024, DOI: 10.48550/arXiv.2501.00536).

“The project started just based on our bad experiences with cacio e pepe,” postdoctoral researcher Daniel Busiello tells Newscripts. After they repeatedly struggled to scale up cacio e pepe for a larger group (the larger the batch, the more the temperature of the pasta will vary and the more likely the sauce consistency will be off), Busiello and his friends decided to apply their scientific expertise to the problem.

They spent a weekend devising an experimental protocol for studying, as scientifically and reproducibly as possible, how changing the temperature, starch concentration, and cheese-to-water ratio affected the ultimate texture of the sauce, using a sous vide apparatus and other kitchen tools, as well as a camera to photograph the results.

Busiello says he and his friends went through about 5 kg of good Italian pecorino cheese, and they didn’t let any of it go to waste. Even when the experiment produced unsightly clumps, they ate the results on bread.

The physicists ultimately determined that the ideal starch concentration is in the neighborhood of 2–3%, a little more than regular pasta water usually contains. Cooks can achieve the proper starchiness by concentrating the pasta water a bit or—for the most reproducible results—by using a stock solution of cornstarch in water.

Cornstarch contains the linear polysaccharide amylose, well-known for its ability to interact with water molecules to form a sauce-thickening gel when heated. It’s “a nice little insurance policy,” says Rosemary Trout, director of the culinary arts and food science program at Drexel University. But, she says, “if you have the right pasta, you don’t necessarily need it.”

In high-end dried pasta, Trout explains, the starch is gelatinized in a protein matrix, which gives the noodles a better bite but doesn’t release as much starch into the cooking water compared with handmade noodles or even run-of-the-mill supermarket pastas. By focusing exclusively on starch and temperature, the researchers didn’t account for the pepper, which isn’t just there for flavor—it contains hemicellulose, which may also help emulsify the sauce, Trout says.

Lord(s) of the (salt) rings

Culinarily savvy folks in the habit of generously salting their pasta water before bringing it to a boil may notice that the grains fall to the floor of the pan in a ring shape. Of course someone’s come up with a scientific explanation for that too (Phys. Fluids 2025, DOI:10.1063/5.0239386).

Fluid mechanics researchers Mathieu Souzy and Pallav Kant, who worked together as postdoctoral scholars at the University of Twente, started getting curious about salt rings while making pasta for a game night a few years ago. They investigated the phenomenon with the help of a high school intern, Clément Vovard. Because they are physicists, Souzy and Kant simplified the problem using spheres. They rounded up spherical glass beads ranging from 0.6 to 6 mm in diameter, dropped them into tanks of water between 5 and 40 cm deep, and observed the shape the beads made when they hit the bottom.

The researchers found that the beads hit the water in a roughly spherical clump, which flattens into a doughnut shape as it drifts downward. Increasing the water depth, number of particles, or particle size resulted in a larger ring. So to make a good salt ring, “the key is to have enough salt in your hand and to tilt it such that all the grains enter the water at the same instant,” Souzy tells Newscripts.

He adds that the experiment is a great teaching tool for introducing students to the basics of fluid mechanics and the scientific process—he’s been contacted by several teachers about using it in lesson plans.

Please send comments and suggestions to newscripts@acs.org.