p-Anisidine value (p-AV)
The AOCS standard method (Cd
18-90) was used to measurep -AV (AOCS, 2011). First, ap -anisidine solution was prepared by dissolvingp -anisidine (25 g) in
acetic acid (100 ml). Oil samples
(about 0.5 g) were weighed into a 25 ml volumetric flask and isooctane
was added to fill the flask. The sample solution (5 ml) was transferred
into a test tube, thep -anisidine solution (1 ml) was added, and the solution was
briefly vortexed. After 10 min, the absorbance was measured in a quartz
cuvette with the same spectrometer used for PV at 350 nm. Isooctane (5
ml) and p -anisidine solution (1 ml) added in a test tube was used
as a blank. When p -AV was over the measurement limit, the
concentration of the sample was reduced to half and the value was
measured again. p -AV of three experimental replicates were
determined.