When the combination of a liquid and a gas becomes a solid

To a physical chemist, a foam corresponds to a colloidal dispersion, or colloid, in which the dispersion medium is a liquid and the dispersed phase is a gas. Although it seems like a simple system, scientists have been trying to understand and predict its fundamental properties for centuries. In 1999, physicists Denis Weaire and Stefan Hutzler published The Physics of Foams, a reference book that compiled available scientific information on foams and encouraged researchers in the field to further study of these dynamic processes. In 2013, mathematicians from the University of California at Berkeley James A. Sethian and Robert Saye published in Science a model of the evolution of a foam in three stages: construction of the structure, flow of the liquid through the thin membranes, and bursting of the foam. the bubble and process restart [see “The Evolution of Foams,” by John Matson; Research and Science, November 2013].

David A. Weitz is one of the scientists who is studying the application of foams in various fields. From the School of Engineering and Applied Sciences (SEAS) at Harvard University, he is developing methods to obtain “designer” emulsions and foams using microfluidic devices. Weitz did not hesitate to organize the Science and cooking course at Harvard in 2010 to take advantage of the creativity that was being generated in the world of gastronomy and transfer it to other areas such as the development of new materials. His conversations with Ferran Adrià about science and gastronomy were exciting.

In the kitchen, foams have been common throughout history. However, until recently they were restricted to dairy products or egg whites and little else. The mousses were the stars. In the nineties of the last century, Adrià began experimenting with new foams using the siphon and dinitrogen oxide (N2O) as incorporated gas. Elaborations such as foie, cod, potato or mushroom foams began to be lavished in the kitchen of the El Bulli restaurant and spread throughout the culinary world. Heston Blumenthal, Wylie Dufresne, Andoni Aduriz, Grant Achatz and many others made them their own and introduced them to their kitchens. The ease of use offered by the siphon favored the arrival of this technique in modest kitchens and bars. It is already common to serve foams at banquets, cocktails and other events.

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