active oxygen method

A classical accelerated test for measuring how resistant a fat or oil is to oxidative rancidity. A sample is held at an elevated temperature, typically around 98 degrees Celsius, while air bubbles through it, and the analyst measures the time until oxidation products appear, detected by the peroxide value or by a sharp rise in conductivity from volatile acids. The longer this induction period, the more stable the fat. Though newer automated instruments have largely replaced the manual apparatus, the principle remains central to shelf-life prediction for frying oils, margarines, and snack foods. Formulators use the results to compare antioxidant systems, evaluate the effect of processing on stability, and set realistic best-before dates, since oxidative rancidity is the main factor limiting how long fat-rich foods stay palatable.