Rancid describes the harsh, somewhat bitter, flavour and odour of oxidised fats. Rancidity is the quality of being rancid. Oxidation of fats results in a variety of chemicals of different types, many of which have strong odours and flavours. These give rise to the rancid sensation. Because rancid flavours are due to mixtures of chemicals, the exact character of rancidity can differ a little among sources of the fat and the extent of oxidation. Refreezing Freezing fish again after it has been thawed or partially thawed as in tempering.