P-Anisidine Value
The AOCS Official Method was used to determine p -anisidine values of oil samples (Society and Firestone, 1994). Briefly, 0.2 g of the oil sample (m) was mixed with 23 ml of iso-octane, and then its adsorption (Ab) was determined at 350 nm. Then 5 ml of this solution was added to 1 mLp -anisidine reagent (25% in glacial acetic acid). The mixture absorbance (As) was read at 350 nm after 10 min stored in the dark at 25 °C. The p -anisidine value was determined by Eq. (11).
AV= 25(1/2As – Ab)/m (11)