Total phenolic content of RBO was measured according to the
method reported by Lai, Li, Lu, and Chen (2009) by using
FolineCiocalteu reagent with some modification. A 0.1 mL RBO
solution (1.0 mg/mL DMSO) was sampled into 2 mL of 0.02 mg/mL
Na2CO3 and mixed for 3 min. After adding 0.1 mL of
FolineCiocalteau reagent, the final mixture was left for 30 min
before reading the absorbance at 750 nm (UVeVIS 1700, Shimadzu,
Japan). All measurements were conducted in triplicate and the data
were expressed as mg ferulic acid equivalent (FAE) per g of the oil
(mg FAE/g oil), based on the calibration curve of ferulic acid.