2.5. Determination of FFA contents
FFA contents as oleic acid were determined by the American Oil
Chemists’ Society (AOCS) official method using phenolphthalein as
an indicator (AOCS, 1997). Sample was dissolved in ethyl alcohol
at 60 ◦C and FFAs contained in the sample were neutralized with
sodium hydroxide solution. The sample mass and the volume of
sodium hydroxide used were used to calculate the contents of FFAs.