Different Kinds of Radiation Carry Different Amounts of Energy

Appears in
On Food and Cooking

By Harold McGee

Published 2004

  • About
Different kinds of radiation carry different energies, and the energy of a given kind of radiation determines the kind of effect that it will have.
  • At the bottom end of the scale, radio waves are so weak that they can only cause increased movement in free electrons. This is why metal antennas and their mobile electrons are necessary to transmit and receive such radiation.
  • Next come microwaves, which are energetic enough to set polar molecules like water moving faster. (Microwave refers to the fact that their wavelength is shorter than radio wavelengths.) Since most foods are mostly water molecules, microwave radiation is an effective means of cooking.
  • Then there’s heat radiation, the cook’s standard energy source, which causes the increased movement of nonpolar molecules—including carbohydrates, proteins, and fats—as well as polar water.
  • Visible and ultraviolet light is capable of altering the orbits of electrons bound in molecules, and so can initiate chemical reactions that cause damage to pigments and fats and the development of stale, rancid flavors. Visible and ultraviolet rays from the sun can ruin the flavor of milk and beer, and ultraviolet rays can burn our skin, damage our DNA, and cause cancer.
  • X and gamma rays penetrate matter and ionize it, or strip electrons from its molecules. Along with controlled beams of certain subatomic particles, they damage DNA and kill microbes, and are used to “cold-pasteurize” and sterilize some foods.