You may have noticed that it’s been more than a week since I posted about Week 2 of the food science course. Well, there was a grading glitch, so they pushed everything back two weeks, and with Christmas and all, it was very easy to take them up on their offer to be lazy. But fear not, Arne and I are still taking the class!
Week 3 focused on phase transitions in food – freezing and melting, as well as the firming up of proteins in food when heat is applied. There were six or seven videos of Joan Roca (of El Celler de Can Roca, “recently voted best restaurant in the world,” though I’m not sure by whom) demonstrating sous vide preparations and a few other things. This was several more than necessary, and unfortunately the videography on the celebrity chef segments is not great – it tends to be done from straight ahead, with few close-ups, so it’s hard to see the great art that’s supposed to be happening. I wish they were more dynamic.
The videos introduced a piece of high-tech kitchen equipment I hadn’t heard of before: the rotovap. Short for “rotary evaporator,” the rotovap strongly resembles a still, and is used for a similar purpose: It extracts volatile compounds from food without heating them up, which would alter their flavors. Joan Roca used it to create a lemon peel distillate for a complex and beautiful lemon dessert.
More excitingly, they used it to create a super-pure flavored liquid that could be chilled to -5 Celsius without solidifying, because it didn’t have enough nucleation points to freeze. A flask of this liquid was presented as a dessert along with a chilled plate of melon and herbs, and when the liquid was poured onto the plate, it was provided nucleation points and instantly froze into a stalagmite. Truly incredible to watch!
The homework dwelled on the differences between pressure cookers, sous vide cookers, and rotovaps, as well as on the effects of solutes (usually sugar and salt) on freezing and boiling points in food preparations. The lab illustrated the latter point with a familiar process – reducing the temperature of water to below 0 degrees Celsius by adding salt, so we could use this super-chilled water to freeze ice cream.
In the lab, we created just about the lowest-tech ice-cream maker imaginable – two Ziploc bags. The inside bag held a solution of cream, milk, sugar, and vanilla; this was surrounded by an ice-and-salt solution in the larger exterior bag. We took turns shaking and massaging the bags (using oven mitts to avoid freezing our hands) until the inside solution turned to ice cream.
I recommend doing this experiment when your hands are free of hangnails and paper cuts. There was salt everywhere! The resulting ice cream was better than we expected – surprisingly creamy. I guess we kept it moving enough. I definitely prefer using a machine, though.
Check back soon for weeks 4 and 5, “Elasticity” and “Diffusion and Spherification.”