Key Lesson: Energy in Cooking. All cooking involves changing the temperature or manipulating the bonds between molecules.
Last week introduced molecules as the basic components of food. Cooking is all about irreversible transformation of these molecules.
This week, we learn about the revolutionary sous-vide techqniue from two of the pioneers in the field: Joan Roca and Salvador Brugués. This technique allows precise control over the transformations that occur in many foods. Jordi Roca uses other types of transformations in his breath-taking desserts.
Overview of this Week's Science
Below are some of the examples of the transformations caused by heat:
Heat causes fats to melt; the melting temperature is higher for longer, more saturated fatty acid chains.
Heat causes proteins to unravel, in a process called denaturation.
Heat causes starches to unravel, a process that chefs called gelation (but we won’t, since it has another meaning in physics).
Equation of the Week
How much energy must be used to raise the temperature of the food by a given amount?
Specific heat, cp defines the energy required to raise the temperature of a material with a mass, m, by a specific amount, ΔT:
$$ U = m c_p \Delta T $$
If a drink with a mass of g and a specific heat of J/(kg K) decreases in temperature by °C, then J of energy must be absorbed by the whiskey rocks.