Rancidfatty

Rancidfatty is a term used to describe fats and oils that have degraded through rancidity. The term is not common in formal science, but it is used informally to reference the state in which fatty substances develop off-flavors and odors due to chemical changes in fatty acids.

Rancidity primarily occurs in two forms: oxidative rancidity and hydrolytic rancidity. Oxidative rancidity involves the reaction of unsaturated fatty acids with oxygen, forming lipid peroxides that break down into volatile aldehydes, ketones, and alcohols. These products, such as hexanal and nonenal, confer grassy, cardboard-like, or fatty odors. Factors accelerating oxidative rancidity include heat, light, exposure to air, trace metal catalysts, and high degrees of unsaturation. Hydrolytic rancidity arises when triglycerides are cleaved by lipases or hydrolysis, releasing free fatty acids. These free acids often have strong, sharp, or soapy flavors and contribute to rancidity. This type is common in aged dairy fats, butter, and products stored with moisture or poorly cleaned processing equipment.

Detection and consequences: Rancidity is assessed by sensory evaluation and by chemical indices such as peroxide value and anisidine value. Nutritional quality and safety can decline as fats oxidize, and some oxidation products may have toxicological concerns at high exposure, though typical consumer exposures are low in ordinary diets.

Prevention and management: To delay rancidity, fats are stored in cool, dark, airtight conditions, away from light and heat. Antioxidants such as tocopherols (vitamin E) and synthetic stabilizers (e.g., BHT, BHA) are used in some products. Proper packaging with low oxygen transmission, refrigeration for high-fat foods, and minimizing exposure to metals can extend shelf life.