Rancidity

Rancidity refers to the deterioration of fats and oils that leads to off odors, flavors, and reduced quality in foods. It can occur in edible fats and oils, fat-containing dairy products, and processed foods. The two main forms are oxidative rancidity, caused by reaction with oxygen, and hydrolytic rancidity, caused by the cleavage of triglycerides.

Oxidative rancidity involves initiation by heat, light, metals, or impurities, followed by a free radical chain reaction. Primary products are lipid hydroperoxides, which can break down into secondary compounds such as aldehydes, ketones, and alcohols that produce characteristic rancid or cardboard-like flavors. Unsaturated fatty acids, especially polyunsaturated ones, are more susceptible to this process. Antioxidants and proper storage can slow oxidation.

Hydrolytic rancidity results from enzymatic or moisture-driven hydrolysis of triglycerides, releasing free fatty acids. This form often contributes sour, soapy, or rancid flavors and is common in dairy products and fats stored under unfavorable conditions.

Detection and prevention are central to managing rancidity. Sensory evaluation remains a primary method for quality control, complemented by chemical assays such as peroxide value, anisidine value, TBARS, and acid value. Prevention strategies include using antioxidants (natural or synthetic), minimizing exposure to heat, light, and metals, and employing protective packaging and inert atmosphere storage. Temperature control, airtight packaging, and dark storage help extend shelf life and maintain flavor stability.

In summary, rancidity is a common spoilage pathway for fats and oils, affecting flavor and safety perceptions. Understanding its mechanisms informs processing, storage, and quality control practices in the food industry.