about 100 mg of oil sample was dissolved in 25 ml of 1-butanol, mixed thoroughly with 5.0 ml of TBA reagent( 200 mg TBA in 100 ml 1-BuOH ) and incubated at 95 n for 2h. after that, the reaction mixture was cooled up to room temperature under running water and absorbance was measured at 530 nm. at the same time, a reagent blank test( without TBA reagent ) was also parallely done.