Oxidative Stability Index (OSI)

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Price of the test:

$115 per analysis

Acceptable Matrices:

Fats and Oils

Unacceptable Matrices:

Non-fat and non-oil samples

Limit of Quantitation:

A temperature should be selected to yield results between 4 and 24 hours. It is recommended that samples running longer than 15 hours be analyzed at a higher temperature. Samples completing in less than 4 hours may have a wider variation of end point determination.

Sample Size Requirements:

Please provide a sample of at least 20g to ensure results representative of sample submitted.


Metrohm Rancimat model 743

Reportable Units:

OSI reported in hours
AOM (Active Oxygen Method) can be calculated from the OSI data

Turn Around Time:

10 Business Days

Is Rush Available?


Method Reference:

AOCS Cd 12b-92 and ISO 6886:2006(E)

Method Description:

This method determines the oxidative stability index in fats and oils. The oil sample is heated at 110°C (unless another temperature is specified), and air is bubbled through it at a flow rate between 8.28-9.72 L/H. The effluent air from the oil or fat sample is then bubbled through a vessel containing ultrapure water. The conductivity is continually measured in the adjoining test tube. The effluent air contains volatile organic acids, swept from the oxidizing oil, that increase the conductivity of the water as oxidation proceeds. Formic acid is the predominant organic acid formed. A computer monitors the conductivity of the water. The Oil Stability Index (OSI) is defined as the point of maximum change of the rate of oxidation, or mathematically of the second derivative of the conductivity with respect to time.

Information Required by Submitter:


Please specify testing temperatures other than 110°C. AOCS and ISO methods suggest 100-140C as appropriate temperatures for analysis. For best results, the temperature used should optimally yield a 4 to 24 hour induction period. A temperature increase or decrease of 10C decreases or increases the induction period by a factor of approximately 2 (reference ISO method 6886:2006 (E))