Development of methods for determining free fatty acid contents in red colored oils

Buah merah oil and red palm oil are red colored and unrefined edible oils. Because of this color characteristic, measuring acid value by titration method can be uncertain and subjective, so more accurate and objective methods are needed. Gas chromatography-flame ionization detector (GC-FID) and high-performance liquid chromatography-evaporative light scattering detector (HPLC-ELSD) methods were developed to determine acid value in 3 buah merah oils and 1 red palm oil by measuring free fatty acid contents. The acid value was high in the order of titration > GC-FID > HPLC-ELSD in all samples. GC-FID method showed accurate and reliable results, whereas HPLC-ELSD showed rough data partly due to the non-linear standard curve and high limit of detection. Difference in acid value between titration method and GC-FID might be due to unrefined components that reacted with KOH titration solution. GC-FID can be used measuring free fatty acid contents in red colored oils. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10068-021-00964-2.