Techniques for detecting adulteration in palm kernel oil
Near infra-red spectroscopy (NIR) is a rapid technique to detect adulteration of crude palm kernel oil (CPKO) by palm oil products and by-products if the level of adulteration is more than 10%. Below this, the technique can detect scavenger, alcohol bottom, ester bottom or soap stock contamination. Determination of solid fat content (SFC) by pulsed nuclear magnetic resonance (PNMR) can be a general technique for detecting adulteration by CPO, refined bleached deodorized (RBD) palm oil, palm olein, RBD stearin, palm residue, scavenger, soap stock, alcohol botom and ester bottom in CPKO at 1% to 10%.
Gas chromatography (GC), by measuring the fatty acid composition (FAC), can detect adulteration by CPO, RBDPO, palm olein, RBD stearin, palm residue, scavenger and ester bottom, but is not suitable for soap stock and alcohol bottom. High performance liquid chromatography (HPLC), by measuring the triglycerides content, is not a satisfactory technique for determining adulteration in CPKO. Physical techniques, such as the cloud point, refractive index and slip melting point, and saponification value are also not suitable. GC and PNMR can detect as low as 0.3% adulteration in CPKO.
However, due to the large national natural variation of FAC and SFC in CPKO, the limits of determination for nine adulterants were only 4.0% to 7.0% by GC and 3.0% to 9.0% by PNMR. One approach to lower the limit of determination is to reduce the natural variation of FAC and SFC of CPKO by assessing adulteration in individual oleochemical plant. With this approach, the limit of determination can be lowered to <, 2.0% by both GC and PNMR.