The Rancimat test is a simple, quick and efficient way to screen the effectiveness of antioxidants used in liquid fats and oils.
The method is an accelerated oxidation test in which the oil or fat to be tested is run at elevated temperatures whilst exposing the sample to air accelerating the oxidation process of the oil. This results in autoxidation in a few hours, instead of weeks or months. Metabolites produced from the oxidation of the oil in the reaction vessel are driven off into a measuring vessel which measures change in conductivity. It is the point at which there is a sudden change in conductivity that indicates the point at which there is the formation of volatile carboxylic acids and oxidation has occurred.
Test conditions and apparatus
Testing is performed typically on a standard Metrohm Rancimat. The temperature of the test is maintained at 100 °C and the air flow at 15l/h.
Typical Results
The results obtained are provided in a way that comparisons between different antioxidants can be made at equivalent rates of addition. An induction period (time taken before oxidation is induced) is measured as the time between starting the test to the point at which the conductivity in the measuring cell changes rapidly. The relative performance of the antioxidants are measured against the control. The control is given a protection factor of 1 based on its induction period and the antioxidants are then compared in terms of protection factor against control.