On exposure to air it gradually absorbs oxygen and darkens in color and develops a more pronounced odour. It decomposes when heated at 80 to 100 °C. 

An unsaturated fatty acid that is the most widely distributed and abundant fatty acid in nature. it is used commercially in the preparation of oleates and lotions, and as a pharmaceutical solvent. Major constit. of plant oils e.g. olive oil (ca. 80%), almond oil (ca. 80%) and many others, mainly as glyceride. Constit. of tall oil.

Also present in apple, melon, raspberry oil, tomato, banana, roasted peanuts, black tea, rice bran, cardamon, plum brandy, peated malt, dairy products and various animal fats. Component of citrus fruit coatings. Emulsifying agent in foods Oleic acid is a monounsaturated omega-9 fatty acid found in various animal and vegetable fats. The trans isomer of oleic acid is called elaidic acid.