Peroxide Value by Titration


Background:  Peroxide Value is commonly used to determine the rancidity of a sample containing fat or oil subject to oxidation.


Method

Apparatus

Turn Around Time

Sample Required

Type of Test

Reportable Units

Measurement Range

AOCS AOAC 965-33 Titration

Burette

5 to 10 Business Days

Enough sample to yield 1.5 to 2.0 g of extracted fat or oil

Titration

mEq/Kg (milliequivalent/Kg) of Fat

Peroxide Value Lower Detection Limit:  0.5 mEq/Kg Fat


Analysis Description:  The fat or oil is dissolved in a chloroform-acetic acid mixture and subjected to an excess of iodide via a saturated solution of potassium iodide.  The peroxides present oxidize the iodide to iodine and the iodine is then titrated to a colorimetric endpoint using sodium thiosulfate with starch as an indicator.  The amount of iodine produced is directly proportional to the peroxide value.

In general fresh oils have a peroxide value of >10 mEq/Kg while peroxide values in the 30-40 mEq/Kg range are generally associated with a rancid taste.