Eight physicists from Padua, Dresden, Barcelona, and Vienna find the optimal combination of ingredients for a foolproof Cacio e Pepe sauce.
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Cacio e Pepe deserves to be counted among the iconic dishes of Italian cuisine and one of the most beloved dishes worldwide. Although a primordial recipe can be found in a fifteenth-century manuscript, the version of Cacio e Pepe that has reached us originates from Roman pastoral tradition and the ease of transport and preservation of the few ingredients involved: cheese, pasta, and pepper. "Despite its apparent simplicity, creating a perfect Cacio e Pepe, smooth and silky, is extremely complex given the microscopic interactions involved," says Daniel Maria Busiello, a researcher at the University of Padua. The study recently published in the journal Physics of Fluids (Phase separation in Cacio e Pepe Sauce, Physics of Fluids 37, 044122, 2025, DOI: 10.1063/5.0255841), concerning the phase separation of liquids, aims to determine the ideal combination of all ingredients involved to obtain a perfect Cacio e Pepe.
On the other hand, pasta, in its variety of shapes and uses, has often been a source of inspiration for scientific research, both from a morphological and more strictly culinary point of view. The cooking water, rich in starch, is often used as an emulsion stabilizer, as in the preparation of the famous spaghetti aglio e olio, as it prevents the separation of the sauce into its fundamental constituents. Phase separation, more generally, plays a crucial role in numerous aspects of the culinary world, in addition to being a particularly active research area in biophysics, thanks to the recent discovery of the presence of membrane-less compartments within the cytoplasm. And it is precisely this phenomenon that makes the realization of Cacio e Pepe so arduous, as the separation of cheese from water at high temperatures is responsible for the formation of the unpleasant lumps that make the recipe a failure.
The team, composed of eight Italian physicists affiliated with institutions across Europe - Max Planck Institute, ISTA, University of Barcelona, and University of Padua - explored the role of all components, starch, water, and cheese, identifying starch as the key factor in making the sauce homogeneous. "We studied more than 200 samples of the sauce for different concentrations of its components and for different temperatures, using simple kitchen tools to conduct the experiments, thus making the study accessible and reproducible," explains Ivan di Terlizzi, a researcher at the Max Planck Institute. This aggregation phenomenon, the study explains, is due to the cheese proteins and their configurational changes when heated. Starch, however, would be able to shield these interactions, favoring much smaller lumps that are not perceptible to the palate - which is ultimately what matters. The study clearly shows that the starch typically contained in pasta water is not sufficient to mitigate aggregation. It is therefore recommended to add powdered starch (appropriately gelatinized) in quantities between 2% and 3% of the cheese weight. "The theoretical apparatus for studying phase separation has made it possible to understand these interactions," adds Fabrizio Olmenda, who works at ISTA as a researcher.
The study concludes with the formulation of the scientifically optimized Cacio e Pepe, giving a practical twist to the theoretical results shown. "No experimental sample was wasted, to the delight of many friends and diners who certified, with the perfected recipe, the success of our research," explains Giacomo Bartolucci, a university researcher in Barcelona.
