Oxidation stability of oils and fats – Rancimat method

The Rancimat method, also called OSI (oxidation stability index), is an accelerated aging test. Air passes through a sample in the reaction vessel at a constant elevated temperature. Fatty acids oxidize in this process. Volatile secondary reaction products form at the end of the accelerated oxidation test. These are transported into the measuring vessel via the air stream and absorb in the measuring solution (deionized water).

The (continuously recorded) electrical conductivity of the measuring solution increases due to the absorption of the reaction products. Thus, their appearance is detected. The time until secondary reaction products are detected is called induction time. It characterizes the oxidation stability of oils and fats.

Determining the oxidation stability of fats and oils is important for quality control in the food industry. Not only can liquid samples be measured by the Rancimat analysis, but also solid foodstuffs. If possible, the oxidation stability of fats and oils in solid foodstuffs is directly measured. If the samples cannot be measured directly, this is achieved by using the isolated fat after cold extraction with petroleum ether.

Furthermore, when OSI testing with the Rancimat, the new PEG method has proven to be the most effective method aside from direct measurement. It is particularly suitable for products with difficult matrices or when time-consuming sample preparation should be avoided.

This Application Bulletin provides a detailed description about all the mentioned Rancimat test methods and its requisite sample preparation steps.

Download AB-204 (EN)