The Physics of Cooking

Len introducing Dave Weitz

Yesterday we attended a public lecture on The Physics of Cooking sponsored by the Aspen Center for Physics, held at one of the veneus of the Aspen Institute. Speaker Dave Weitz began with  a detailed description of the course he teaches at Harvard on science and cooking, and on the various collaborators he has worked with, beginning with very famous chef Ferran Adria of Barcelona.

Weitz then discussed and demonstrated several topics in the physics of cooking, including brief summaries of egg-cooking; using a pressure cooker (which was invented, he said, by the British Royal Society); distilling and super-cooling a liquid to make a sort of tower of ice; measuring the elasticity of boiled eggs or broiled steaks; using gels in post-modern cooking processes; understanding foams; and finally, a bit of the physics of mixing a drink.

Freezing an egg in liquid nitrogen: Carolyn Boyd, student helper with Dave Weitz

Using three sous-vide cookers Dave demonstrated the difference between eggs cooked precisely to three very close temperatures -- 61, 63, and 65 degrees Celsius, and how the protein in the egg reacted to the different temperatures. Results: a watery egg, an semi-watery egg, and an egg that looked like a regular poached egg with a soft but solid white and oozy yolk. Caroline Boyd walked two of the eggs around the audience in the fairly large hall so that we could see the difference.

Aspen Chef Robert McCormick demonstrates how to encapsulate cucumber juice in
a thin membrane using agar and Ca2. Result "cucumber caviar."

After McCormick's demo of cucumber caviar, a gel, Dave briefly discussed foams like beer foam, whipped cream, and ice cream, pointing out that whipping cream with a whisk made a more stable foam than the faster method of injecting gas, using a device that appears in the photo above (in front of McCormick's apron).

Local bartender Jimmy Yaeger gave the final demonstration of how to mix a Negroni and how to make a perfectly clear and spherical ice cube (using very elaborate though low-tech equipment).  Yaeger uses a water-circulating ice freezer to make giant blocks of perfectly clear ice -- the circulating device removes the air bubbles that make ordinary ice cubes cloudy. He saws up the big ice block into various-sized ice cubes to provide a distinctive touch for the drinks in his bar. I was very interested in the copper pressure device used for processing a 3 inch cube of ice into a spherical ice cube. The heat-conducting property of copper causes the corners of the cube to just melt away!

After the end of the talk was an outdoor demo of making ice cream in sealed plastic bags surrounded by another baggie of ice and salt.