Peroxide value (PV)
A ferric-thiocyanate based spectrophotometric assay was used as previously reported (Shantha & Decker, 1994) for the determination of PV, with the following modifications: the assay volume was proportionally reduced to 3.0 ml, oil sample size was reduced to 10 mg, and a mixture of methanol/isopropanol (2:1 v/v) was used as the solvent to avoid using chloroform. Absorbances were measured using a PerkinElmer Lambda 35 UV/Vis spectrophotometer (Perkin Elmer, Waltham, MA, USA) at 510 nm. Ferric chloride solutions (1-15 µg Fe3+/ml) in methanol/isopropanol (2:1 v/v) were used for the standard curve. Three experimental replicates were analyzed in duplicate.