Cacio e Pepe – literally cheese and pepper – is a pasta dish from the Lazio region of central Italy that consists of just Pecorino Romano cheese, black pepper, tonnarelli pasta and water. And it is a fabulously smooth, creamy dish. Yet every Italian chef knows this simplicity is deceptive. Get the proportions of ingredients wrong and Cacio e Pepe quickly becomes a soggy, lumpy mess. Perfecting the dish is surprisingly tricky, but how come?Now we get an answer thanks to the work of Giacomo Bartolucci at the University of Barcelona and colleagues who have explored the complex behavior of the emulsion that forms when pecorino cheese is added to water used to cook pasta, which is filled with starch. It turns out that the proportion of cheese, the amount of starch in the water and the temperature must all be carefully controlled to achieve the perfect result. Perfect PastaBartolucci and co say that through careful experimentation, they have finally determined the perfect conditions. “We present a scientifically optimized recipe based on our findings, enabling a consistently flawless execution of this classic dish,” they say.Food scientists have long been both fascinated and puzzled by the complex behaviors of edible foams and emulsions such as mayonnaise, ice cream. A typical recipe for Cacio e Pepe is simple. Cook the tonnarelli — a spaghetti-like pasta — in boiling, salted water until it is al dente, soft but chewy. Set aside a cup of this pasta water and slowly add it, while stirring, to a large bowl of the grated Pecorino cheese and black pepper. Finally, add the pasta allowing the creamy mixture to entirely coat it and serve hot. Ecco qui! Don’t be surprised, however, if your delicious creamy sauce separates into a revolting lumpy paste. What this recipe fails to explain is that the cheese will separate and form into clumps under a wide range of seemingly ordinary conditions.Cheese is a complex colloidal system, composed of proteins, fats, and water. When Pecorino Romano is mixed with hot water, the proteins must remain finely dispersed to create a smooth emulsion. If they aggregate, they form clumps, ruining the texture of the sauce.Temperature plays a crucial role in this process. If the cheese is added to water that is too hot, its proteins denature and coalesce into large, rubbery clumps. To find the perfect conditions, Bartolucci and co systematically measured the effects of changes in starch concentration, cheese-to-water ratio, and temperature. They heated mixtures under controlled conditions, capturing images of the resulting emulsions at different temperatures. By quantifying the size and distribution of protein aggregates, they constructed a phase diagram illustrating the boundaries between smooth sauce and clumpy separation.The results will be hugely useful for any chef or would-be food scientist. They confirm, for example, that cheese added to water alone forms system-wide clumps at around 65&
I fisici svelano il segreto della salsa perfetta per la pasta.
