A standardised amount of sample is placed in a sealed vessel under elevated oxygen pressure. The test may be accelerated using elevated temperatures. The start of the fat oxidation process is characterised by a distinct increase in the rate of consumption, caused by the generation of hydroperoxides, manifesting as a visible drop in oxygen pressure. See figure 1. By following the oxygen pressure over time, the sample induction period (IP) is determined. This sample specific IP can be regarded as an indication of the oxidative stability of the sample and is indicative of the onset of oxidative rancidity. A longer IP means better antioxidant performance and therefore a more stable product. Sample B from our example has a longer IP and therefore better stability and a longer shelf life.
