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.
