We heat very briefly to about 190 degrees in order to release the oil from the meat. The total heat exposure lasts about 5 minutes, after which the extracted, clean oil is rapidly cooled to ambient temperature.
Important Note: unlike olive and other vegetable oils, fish oil CANNOT be “cold pressed” (good luck trying to press oil out of a cold fish!). 🙂 Some fish oil marketers use that term (incorrectly) to promote their oils, but that term is merely borrowed from vegetable oil processing, where cold pressing is a normal process.
The short heating of the oil also acts as a form of pasteurization ensuring stability of the oil.