Rancidity is a condition which is related to unsaturated fats present in the food items. The aerial oxidation of the unsaturated fats present in the food items over long exposure to environment which leads to unpleasant odor and flavor is called as rancidity.

The fatty substances present in the food gets converted to hydroperoxides due to long exposure to air and this hydroperoxides gets decomposed to give aldehydes, ketones and hydrocarbons. Some of this decomposed organic compounds have unpleasant odor and flavor thereby degrading the quality of food item.