2.4. Peroxide Value

The peroxide value was measured according to the method of Wheeler [12] and DGF C-VI 6a [11] by using an automatic titration unit (Titrino plus 848, Metrohm Inula GmbH, Vienna, Austria) with electrochemical endpoint determination. In brief, 2.5 g margarine were melted at 50 °C and dissolved in 20 mL acetic acid and isooctane (3:2, v/v). A total of 200 µL of a saturated potassium iodide solution was added. The sample was stirred and 80 mL bidestilled water were added.

The titrant solution (1 mM Na₂S₂O₃) was added automatically until the equivalence point was reached. The peroxide value was then calculated automatically from the titration unit and indicated in meq O₂/kg oil. Samples were measured in quadruplets.