On Food and Cooking

bond once it’s formed. When the atoms in a
molecule are heated up so they move with the
same kinetic energy that they had released
when they bonded to each other, then those
bonds begin to break apart, and the molecule
begins to react and change.
The strong covalent bonds typical of our
major food molecules — proteins,
carbohydrates, fats — are broken by about
100 times the average kinetic energy of
molecules at room temperature. This means
that they break very rarely at room
temperature, and don’t change at a significant
rate until we heat them. The weaker,
temporary hydrogen and van der Waals bonds
between molecules are constantly being
broken and re-formed at room temperature,
and this welter of activity increases as the
temperature rises. This is why fats melt and
become thinner in consistency as we heat
them: the energy of their motion increasingly
overpowers the forces attracting them to each