Meat kebab. Thermogram of a cooked meat kebab on a plate. The colours show variations in temperature. The scale runs from white (warmest), through red, yellow, green and blue to purple (coldest). Thermography records the temperature of surfaces by detecting long-wavelength infrared radiation. The meat is not uniformly hot, and this may lead to food poisoning if pathogenic micro-organisms have not been killed by the cooking. Heat from the kebab has also caused a heat shadow on the plate (blue streaks).