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 Useful Heat Radiation Is Generated by High Temperatures Because all molecules are vibrating to some extent, everything around us is emitting at least some infrared radiation all the time The hotter an object gets, the more energy it radiates in higher regions of the spectrum So it is that glowing metal is hotter than metal that does not radiate visible light, and that yellow-hot metal is hotter than red-hot It turns out that the rate of infrared radiation is relatively low below about 1,800ºF/980ºC, or the point at which objects begin to glow visibly red Cooking by radiation is thus a slow process except at very high cooking temperatures, those characteristic of grilling and broiling near glowing coals, electrical elements, or gas flames At typical baking and frying temperatures, conduction and convection tend to be more significant than infrared radiation But as the oven temperature goes up, the proportion of heat contributed by the radiating oven walls goes up with it The cook can control this contribution by moving the food close to the walls or ceiling to increase it, or ... frying temperatures, conduction and convection tend to be more significant than infrared radiation But as the oven temperature goes up, the proportion of heat contributed by the radiating oven walls...around us is emitting at least some infrared radiation all the time The hotter an object gets, the more energy it radiates in higher regions of the spectrum So it is that glowing metal is hotter than metal that does not radiate... proportion of heat contributed by the radiating oven walls goes up with it The cook can control this contribution by moving the food close to the walls or ceiling to increase it, or