Periodic cooking of eggs

Who hasn't heard themselves say, at least once, "You don't even know how to cook an egg"? And yet, research from the Federico II University led by Professor Ernesto Di Maio and carried out by lead author, Emilia Di Lorenzo, a doctoral student at the Federico II University, shows that perhaps, cooking an egg, is not as simple as people think.

The study was published in Communications Engineering (Nature Publishing Group).

The egg is a naturally biphasic system: the yolk and the albumen, which constitute it, are two completely different materials. The former is rich in proteins, fats, nutrients and cooks at a lower temperature (65°C), the latter consists mostly of water and proteins and cooks at a higher temperature (85°C). This simple fact results in an equally simple consequence: by cooking at a constant temperature, we cannot have an excellent yolk and albumen at the same time: in the hard-boiled egg, cooked at 100C, we have a perfectly solid albumen, but a floury yolk; in the sous vide egg, cooked at 65C, we have an exceedingly creamy yolk, but a liquid albumen.

The challenge posed to researchers at FoamLab, the Foam Laboratory at the Federico II University, within the Department of Chemical, Materials and Industrial Production Engineering, was, then, to impose two different temperatures in the two different parts of the egg, but without cracking open the shell.

Taking a cue from previous research, the goal was achieved by imposing a periodic boundary condition in the energy transport and simultaneous gelation problem that well describes the cooking phenomenon. Mathematical modeling of the problem and its subsequent simulation allowed the new cooking procedure to be designed in detail: to allow the development of a nontrivial thermal profile inside the egg, it must first be placed in boiling water for two minutes, then in water at 30°C for an additional two minutes, and so on, alternately, for 8 times, for a total of 32 minutes. The new method is called "periodic cooking," and not only succeeds in the feat of cooking at two different temperatures, giving the two phases their respective optimal textures, but also stands out for its incredible ability to preserve nutrients within the yolk, especially when compared with other, more common cooking techniques.

The project, which involved specialists in a variety of fields, from nutraceutical analysis, led by Professor Antonio Randazzo's group in the Department of Pharmacy, to sensory analysis, via materials engineering, is a perfect scientific exercise: it teaches us something about the world around us, but it is also a source of new, fresh, innovative ideas. The possibility of applying this same approach in the design of materials that do not have "layers of textures," but "layers of morphologies and properties" is what FoamLab is now aiming for, in the hope of succeeding in the enterprise of designing a more recyclable and sustainable world.