Determination of oxidative stability of oils and fats

In a new approach to evaluating the oxidative stability of oils and fats, t he consumption of oxygen by a sample confined in a reactor of adjustable te mperature is monitored with a gas-phase now injection analysis (FIA) system . Temperature-dependent data are collected in a low-oxygen-content atmosphe re. For a variety of samples, log(oxygen consumption) is linearly related t o the reciprocal of the absolute temperature (minimum linear r(2) > 0.99). This makes it possible to extrapolate the temperature-dependent data to pre dict the stability of the samples at other temperatures, e.g., typical ambi ent storage temperatures at which the direct determination of oxidative sta bility would be too slow for most samples. The proposed method is instrumen tally simple and is easily automated. The sample throughput rate is an orde r of magnitude faster relative to current alternatives; temperature-depende nt stability characterization for a sample (three temperatures, triplicate measurement at each temperature) requires less than or equal to 2 h. The re producibility of the results is excellent. For a cottonseed-oil sample stud ied over 3 days, the slope and intercept of the log(Oz consumption) vs 1/T linear plot (for all the 45 measurements made) exhibited uncertainties of 2 .1% and 2.0% for the slope and the intercept, respectively, with a linear r 2 value of 0.9929, In a high-temperature (160 degrees C) oxidation experime nt with various oils, the oxygen consumption was well-correlated (linear r( 2) 0.9692) with the concomitant decrease in iodine absorption number (IAN), In contrast, it was poorly and negatively correlated with an increase in t he peroxide value.