ISO 6886:2016 pdf download

ISO 6886:2016 pdf download.Animal and vegetable fats and oils — Determination of oxidative stability (accelerated oxidation test)
1 Scope
This International Standard specifies a method for the determination of the oxidative stability of fats and oils under extreme conditions that induce rapid oxidation: high temperature and high air flow. It does not allow determination of the stability of fats and oils at ambient temperatures, but it does allow a comparison of the efficacy of antioxidants added to fats and oils. The method is applicable to both virgin and refined animal and vegetable fats and oils. Milk and milk products (or fat coming from milk and milk products) are excluded from the scope of this International Standard. NOTE The presence of volatile fatty acids and volatile acidic oxidation products prevents accurate measurement.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 661, Animal and vegetable fats and oils — Preparation of test sample
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1 induction period
time between the start of the measurement and the time when the formation of oxidation products rapidly begins to increase
3.2 oxidative stability
induction period, expressed in hours, determined according to the procedure specified in this International Standard
Note 1 to entry: A temperature of 100 °C to 120 °C is usually applied for the determination of oxidative stability.
Depending on the oxidative stability of the sample under test, or when an extrapolation of regression is required,the determination may be carried out at other temperatures. The optimal induction period is between 6 h to 24 h. A temperature increase or decrease of 10 °C decreases or increases the induction period by a factor of approximately 2.
3.3 conductivity
ability of a material to conduct electric current
4 Principle
A stream of purified air is passed through the sample, which has been brought to a specified temperature. The gases released during the oxidation process, together with the air, are passed into a flask containing water that has been demineralized or distilled and contains an electrode for measuring the conductivity. The electrode is connected to a measuring and recording device. The end of the induction period is indicated when the conductivity begins to increase rapidly. This accelerated increase is caused by the accumulation of volatile fatty acids produced during oxidation.