Peroxide Number of Edible Oils and Fats: Easy Titration

Peroxide number gives the measure of rancidity in oils, fats and margarine. The number of R-OOH is determined using Iodometric titration. The amount of liberated iodine is titrated against sodium thiosulphate and is determined using combined platinum ring electrode.

Reaction:

- Generation of hydroperoxides: R-H + O₂ → R-OOH (Reaction I)

- Generation of iodine: KI + CH₃COOH → HI + CH₃COO-K+ (Reaction II)

                                     ROOH + 2HI → ROH + H₂O + I₂ (Reaction III)

- Titration step: I₂ + 2Na₂S₂O₃ → Na₂S₄O₆ + 2 NaI (Reaction IV)This application is used to determine the peroxide number in edible oils and fats. An excess of iodide solution is added to the sample that is dissolved in nonpolar solvents. The generated iodine is back titrated with sodium thiosulfate titrant monitored by potentiometric measurement with a Platinum sensor. The inflection point of the titration curve is evaluated to determine the equivalence point (EQP).