Few things are as impressive to dinner party guests as a perfectly executed à la minute pasta dish.
As a Roman-born foodie, I would argue that cacio e pepe, a Roman pasta recipe that is as delicious and simple as it is finicky, is a bold menu choice for the novice cook.
The name says it all: pasta, cacio (cheese) and pepe (pepper). That’s it. That’s the recipe.
“The main challenge lies in achieving a stable emulsion: If the cheese is overheated or the starch-water balance is wrong, the sauce will separate,” Massari said.
When that happens, the pecorino forms a gloopy cheesy mess, sticking to everything but the noodles — sad and naked.
So, how can one reliably avoid unpleasant dinnertime disasters? Either by practicing a lot — and inevitably making mistakes in the process, as I have — or by using science to guide the way.
Eight Italian physicists collaborated to crack the code of a foolproof cacio e pepe recipe, studying the properties of cheese, starch and water at different temperatures to learn how to replicate a flawless dish every time.
The study was published April 29 in the journal Physics of Fluids.
The magic trick? Adding a precise amount of cornstarch relative to the overall quantity of cheese used, to keep the dreaded clumps at bay.
When I first heard about the method, the Roman cuisine purist in me was skeptical.
Too many times, I’ve read cheat sheets for the perfect carbonara dish in which the solution to perfect, non-scrambled-egg sauce is to add cream (please, do not do this). In the interest of objectivity, I had to test the recipe myself and talk to these fellow Italians behind the research.
Making big batches of cacio e pepe
In a conversation in Italian, three of the study authors shared that the research came from their frustration for one too many cacio e pepe dishes gone wrong. Thanks to the group’s familiarity with the concept of “liquid-liquid phase separation,” they knew how to investigate the problem scientifically.
“At some point, the eight of us were all at the Max Planck Institute in Dresden (Germany), some as PhD students, some as postdocs,” said study coauthor Daniel Maria Busiello, a statistical physicist at Italy’s University of Padova. At that time, “something we’d often do was cooking Italian recipes, not just for Italians, but for others as well.”
Making big batches of cacio e pepe to feed other hungry scientists turned out to be a near-impossible feat. “There were problems with controlling the temperature of the sauce and of the noodles, causing these clumps,” Busiello said.
“I remember a time the dish came out inedible. Something clicked then,” said study coauthor Ivan Di Terlizzi, one of the group’s top cooks, and a statistical physicist at the Max Planck Institute for the Physics of Complex Systems in Dresden.
The physics of a pasta problem
Di Terlizzi approached fellow researcher Giacomo Bartolucci, now a biophysicist at the University of Barcelona in Spain, with a working theory about possible commonalities between the behavior of cacio e pepe sauce and that of aqueous solutions of proteins inside cells. Bartolucci had focused on phase separation and the aggregation of proteins for his doctoral research.
The scientists set out to understand whether the cheese and water in this recipe could be scientifically described as “a system that undergoes phase separation at high temperatures,” in Busiello’s words.
“We had a theoretical framework and a practical problem,” Busiello added.
Innovating on traditional Italian recipes, even on solid scientific grounds, is a high-risk endeavor. Given the touchy subject, the study authors are of course all Italians, by design.
“If we have to piss off a bunch of people, at least let it be eight Italians who did it,” Di Terlizzi said.
To investigate the behavior of cacio e pepe sauce under heat, the researchers conducted experiments recreating the cooking process in a controlled setup.
“We prepared small batches of sauce using precise amounts of cheese, starch, and water, and gradually heated them using a sous vide device to carefully control the temperature,” Di Terlizzi explained.
“At each stage, we took a small sample of the sauce, placed it in a petri dish and photographed it from above to observe how clumps formed. This allowed us to track how changes in temperature and ingredients affected the smoothness of the sauce.”
Avoiding the ‘Mozzarella phase’
The researchers found that the concentration of starch in the sauce is the key factor influencing its stability. If the proportion of starch falls below 1% of the total cheese weight, the cheese will enter what the authors call the “Mozzarella phase” — in which clumps are inescapable and the dish is ruined — at lower temperatures. A 2% to 3% starch-to-cheese ratio yields the best results.
In the recipe for two published in the study, the researchers used 5 grams (0.18 ounce) of cornstarch or potato starch dissolved in water, heated up gently to form a gel, then cooled down with more water before being blended with 200 grams (7 ounces) of pecorino cheese.
Sodium citrate, a common additive used to make smooth mac and cheese, also worked well in their recipe, although according to Di Terlizzi it lent the dish a slightly “cheese single” aftertaste.
The scientifically engineered pecorino cream can withstand temperature changes better than the classic cheese-starchy water mixture made with pasta cooking water and can even be reheated.
Temperature is in fact another key factor that can make or break the sauce, which has to do with how the proteins in the cheese behave when heated.
“The sauce is stable if created at low temperatures and the starch bonded with the proteins. If, after that happens, you expose the sauce to high temperatures, proteins can no longer interact,” Di Terlizzi said.
If the emulsion of cheese and starch happens at high temperatures though, “there’s no guarantee that proteins will bond with other proteins, which causes the aggregation, before they bond with the starch.”
The scientifically optimized recipe will yield solid results for large batches of pasta, as the stable sauce will give you more flexibility dealing with a large volume of piping hot noodles, cooling down more slowly than a smaller batch of pasta would.
When trying the scientifically optimized recipe, don’t throw away all the pasta cooking water! You’ll still need some of it in the final mixing of all ingredients (the “mantecatura” in Italian). Just be careful to let it cool down slightly.
Testing the physicists’ recipe
When I tested the recipe, the instructions felt straightforward, and the process was quick, though it required a few more steps than what I’m used to (such as forming the starch gel on the stove).
It was frankly odd to work with a pecorino cream that felt so smooth — it almost reminded me of a jarred sauce. Nothing changes as far as the pepper goes. Just crack as much of it as you’d like and toast it in a pan to release its aroma.
My husband and I enjoyed the dish. It tasted great, and dealing with a pecorino cream that needs much less babying at the stove and allows for a much less time-sensitive mantecatura is a definite plus. Also, who doesn’t love the idea of a cacio e pepe party for a crowd?
My only qualm is that knowing there was starch added in the sauce, my perception of the dish’s mouthfeel was definitely skewed, but that wasn’t the case for my husband.
As a proud Roman home cook, my pursuit of a perfect classic cacio e pepe will be a life-long experiment, but the scientifically optimized recipe exceeded my expectations and would be a good initiation for home cooks who have been put off by the dish’s treachery thus far.
A chef’s advice for the traditional dish
But what exactly makes the traditional way of making this dish, by emulsifying the cheese with pasta cooking water, so challenging?
It’s practically impossible to know just how much starch is naturally present in the pasta cooking water, so the success of the crucial emulsion is more of a gamble, but there are tricks to mitigate catastrophe.
One, coming from Massari, is to use less water to boil the pasta.
“For cacio e pepe, I recommend using about 6 to 8 cups of water for 7 ounces of pasta, which translates to a ratio closer to 1 part pasta to 6–7 parts water by weight — significantly less than in traditional pasta cooking,” the chef said.
A classic rule of thumb for cooking pasta, according to Massari, is to use about 1 quart of water for every 3½ ounces of pasta, and 2 teaspoons of salt.
The researchers, who used an arbitrary 10-to-1 ratio of water to pasta in their experiments, also said that reducing that volume of water by two-thirds generally concentrated the natural pasta starch to a safe degree.
Massari also recommends emulsifying the cheese and pasta water below 60 degrees Celsius (140 degrees Fahrenheit), which is in line with the new study’s findings on temperature.
“I first create a cold cheese cream, using finely grated Pecorino and a small amount of the pasta’s starchy cooking water, blending until smooth. Then, I toss the pasta off the heat with the cream and freshly cracked black pepper, adding extra water to adjust the texture,” Massari said. “The result should be a silky, cohesive sauce that clings beautifully to every strand of pasta, not a broken or heavy coating.”
“The natural starch from properly handled pasta is more than sufficient to achieve a creamy, stable, and authentic sauce without compromising the nutritional integrity of the dish,” Massari added.
Another chef’s trick to buy you some time while attempting the recipe the traditional way is “pasta regeneration” — which involves partially cooking the pasta for about 70% of its time, immediately shocking it in ice water to stop gelatinization and finishing it later before serving.
“This method preserves al dente texture while enhancing the final release of surface starch, which is crucial for stabilizing delicate emulsions,” Massari explained.
Celebrating with their tested recipe
The researchers said their scientifically optimized recipe has surged to meme status, online and offline.
“We won’t say we invented the definitive method,” Di Terlizzi said, but this method will save you from ruining good, expensive and hard-to-source pecorino cheese.
For the researchers, that’s personal: “We’re in Germany. We have that shipped to us all the way from Italy. We can’t just buy it at the store every day,” Di Terlizzi said. “So, when the dish turns out badly, that bothers us.”
A big pasta dinner celebrated the publication of the paper, with the researchers preparing at least 4 pounds of pasta for a crowd.
“We were on pins and needles because our diners all knew about the experiment — but it worked perfectly,” Busiello said.
Bartolucci added, “That was our trial by fire.”
The scientifically optimized cacio e pepe recipe we tested
Serves 2
Ingredients
• Salt
• 5 grams (2 teaspoons) cracked black peppercorns, plus more for serving
• 5 grams (2 teaspoons) cornstarch or potato starch
• 200 grams (1 ½ cups, firmly packed) pregrated Pecorino Romano DOP (such as Fulvi, Locatelli or Cello), plus more for serving
• 300 grams (10.6 ounces) pasta, preferably tonnarelli (spaghetti or rigatoni also work well)
Instructions
1. Bring a large pot of lightly salted water to a boil.
2. While the water comes to a boil, add peppercorns in a single layer to a dry pan over medium-low heat. Toast until fragrant, 1 to 2 minutes. Remove pepper from heat immediately.
3. Make the starch gel. In a small saucepan, dissolve the cornstarch by whisking it into 50 grams (3 tablespoons plus 1 teaspoon) cold water. Heat the mixture gently over low heat until it thickens and turns nearly clear. Remove the starch gel from heat and whisk in 100 grams (6 ¾ tablespoons) water to cool. The mixture will return to a liquid state.
4. Make the pecorino cream. Add the starchy water, grated cheese and peppercorns to the bowl of a food processor and pulse to combine until a smooth cream forms.
5. Cook the pasta according to the package directions until al dente, reserving 237 milliliters (1 cup) of pasta water before draining. Drain the pasta and let cool for up to 1 minute.
6. Mix the pasta with the sauce, ensuring even coating, and adjust the consistency by gradually adding pasta water as needed. Keep the sauce slightly runny as it tends to thicken as it cools. If needed, the dish can withstand gentle reheating (up to 80 or 90 C, 176 to 194 F) to reach serving temperature.
7. Sprinkle with additional grated cheese and pepper and serve immediately.
Chef Michele Casadei Massari’s Cacio e Pepe
You can find matt spaghettoni, Sarawak black peppercorns and Pecorino Romano DOP at online specialty stores.
Serves 2
Ingredients
• Sea salt, preferably coarse Sicilian sea salt
• 5 grams (1 teaspoon) freshly cracked Sarawak black peppercorns, plus more for serving
• 100 grams (1 cup, firmly packed) pregrated Pecorino Romano DOP (such as Fulvi, Locatelli or Cello), plus more for serving
• 200 grams (7 ounces) spaghettoni, preferably matt durum wheat spaghettoni
Directions
1. Bring 6 to 8 cups of lightly salted water to a boil in a large pot. Toast the black pepper in a dry pan over medium-low heat until fragrant. Remove pepper from heat immediately.
2. Cook the spaghettoni according to the package directions until slightly al dente, reserving 237 grams (1 cup) of cooking liquid while it’s cooking.
3. While the pasta is cooking, prepare a cold emulsion by mixing grated Pecorino Romano with a small ladle of warm pasta water (ideally under 60 C, or 140 F) in a medium bowl until it forms a creamy base.
4. Drain the pasta slightly al dente, then transfer it to the pan with the pepper.
5. Toss the pasta with the Pecorino cream, gradually adjusting with more pasta water to create a glossy, smooth sauce that perfectly coats the noodles. Add more black pepper and cheese before serving. Serve immediately.