Students at Harvard who are studying the science of cooking learn techniques from guest chefs who stop by, like Carles Tejedor from Barcelona, shown with Amy Rowat, a researcher.
By KENNETH CHANG
Published: October 19, 2010
CAMBRIDGE, Mass.
Multimedia
Video: Harvard Lectures on Science and Cooking
On YouTube, lectures from a public series given in connection to the undergraduate course, with Ferran Adrià, Harold McGee and others.
Partial Syllabus From the CourseIN a basement laboratory at Harvard, Ashley Prince read from the instructions as her lab partner, Allan Jean-Baptiste, poured fruit nectar into a pot.
“Heat it to 113,” Ms. Prince said.
Then Mr. Jean-Baptiste added a mix of sugar and pectin, and Ms. Prince whisked.
“So far, so good,” Ms. Prince said.
These Harvard students were making chewy fruit gelées for From Haute Cuisine to Soft Matter Science, an undergraduate course that uses the kitchen to convey the basics of physics and chemistry, a most unusual Ivy League approach to science.
Each Thursday, David A. Weitz, a physics professor, or Michael P. Brenner, a professor of applied mathematics, covers the science concepts. On the following Tuesday, one of a select group of top chefs, some well versed in kitchen technology — like Wylie Dufresne, of WD-50 on the Lower East Side of Manhattan, or Grant Achatz, of Alinea in Chicago — talks about cooking techniques that illustrate the science.
Besides the laboratory work — the week before the fruit gelées, the students made ceviche; the week after, molten chocolate cake and ice cream — the students also work on projects tackling some sort of culinary science conundrum.
The guest chefs have suggested ideas and problems that they hope the students can solve.
Mr. Dufresne and the other chefs at WD-50 have concocted Parmesan noodles for the fall menu, but the texture deteriorates too quickly.
“They’re e-mailing and calling, ‘Is there any team you have yet that can run this project?’ ” said Amy Rowat, a postdoctoral researcher who is also involved in putting together the course.
Mr. Achatz wants help with some dessert geometry. At Alinea, some desserts are served by pouring them onto a latex sheet draped on the table. Cream will pool into the expected circular puddle. But chocolate flows, to spectacular effect, into a square puddle, and Mr. Achatz would like to know why.
The projects will culminate in a science fair in December, at which the students will be judged on their science (by the instructors) and the culinary presentation (by chefs including David Chang, of the Momofuku restaurants).
For Mr. Jean-Baptiste, a junior majoring in economics, it’s been an introduction to two worlds. “I think I will start to cook,” he said. “I actually think I will take more science classes.”
His gelée experiment was part of a lesson on elasticity (how easily a solid, like gelatin, can be squeezed or pulled) and viscosity (whether a liquid flows fast or slow).
Dr. Weitz also used a steak to demonstrate elasticity, measuring its thickness, applying some weight to it and seeing how much it was squeezed.
“A steak is a spring,” he said enthusiastically. “We’re going to understand the difference between a raw, rare and well-done steak. Tofu has exactly the same behavior. It’s all the same.”
Cooks increase the viscosity of gravies and sauces by using flour and cornstarch as thickeners. In recent years, some chefs have manipulated the textures of their dishes by tapping ingredients from the processed-food industry like xanthan gum and guar gum.
To show how that worked, Dr. Weitz had a brainstorm in the morning, saying in an e-mail to Dr. Rowat, “Please bring spaghetti.”
Pouring cooked spaghetti out of the pot, Dr. Weitz explained to the students that the strands entangle and rub against one another and that the friction slows their movement, increasing the viscosity. In the same way, the proteins in flour, cornstarch and xanthan gum also increase viscosity and thicken the liquid.
If the spaghetti strands — or these proteins — stick together, the liquid turns into a gel.
In the laboratory, as their fruit gelées were cooling and solidifying in a freezer, the students measured the viscosity of water mixed with varying amounts of guar gum and the elasticity of blocks of gelatin.
The experimental apparatus was an improvised mash-up of science and cooking tools. To measure the viscosity, the liquids were poured into measuring columns — standard equipment for a chemistry lab. The funnels were upside-down mustard squeeze bottles with the bottoms cut off.
This particular week, Carles Tejedor, the chef at Via Veneto in Barcelona, had flown in to give the Tuesday lecture. He stopped by the laboratory to see what the students were doing and then started experimenting himself.
In his kitchen, Mr. Tejedor has been developing olive oil jellies. A tiny bit of xanthan gum can thicken water but does nothing when added to olive oil. But if he first made a mixture of water and xanthan gum and then blended in olive oil, the result would be olive oil jelly.
In the Harvard lab, he did something similar but with guar gum, a thickener he had not used before.
“And it’s really good,” Mr. Tejedor said. “It’s like crème brûlée.”
(The guar gum was actually a second choice of the instructors. Originally, the lab was to use xanthan gum solutions, but “at high concentrations, it has strange properties we couldn’t explain,” Dr. Rowat said.)
Explaining how all this works — why, say, honey is viscous and sugar water is not — has turned out to be a tough task, even for the professional scientists.
“What we realized is we also don’t completely understand it,” Dr. Weitz said. “We learn a lot in trying to explain it.”
The science-of-cooking class grew out of a visit to Harvard a couple of years ago by Ferran Adrià, the wizard chef of El Bulli in Spain. At the time, Harvard was looking to revamp and revitalize the core undergraduate curriculum, and the idea of such a class popped up. Mr. Adrià liked the idea, and his foundation collaborated on the course material, which covers the phases of matter, thermodynamics and the various chemical reactions that turn ingredients into food.
The subject material appealed to the students as well, many of whom are history or political-science majors yet to take a science course.
Nearly 700 students wanted to enroll. By lottery, 300 got in. (Dr. Brenner noted to the students that the chance of getting into the class, about 43 percent, was still much better than the chance of getting a reservation at El Bulli.)
A “Top Chef” aesthetic has already made its way into the laboratory. Madison Shelton, a senior, cut her finished gelée into various shapes and attempted to stand them up on a rectangular white shape, just as on the television cooking shows. The soft gelées, however, did not stand up straight, but leaned to the side.
“If you have time, you ought to figure out the elasticity of your jellies,” said Tom Dimiduk, a physics graduate student and one of the teaching assistants for the lab section.
Ms. Shelton took no heed of that suggestion. “I need to make more shapes — a star,” she said, and she cut a star out of the gelée, then a heart, and added them to the plate.
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