Property determination, FA composition and NMR characterization of palm oil, used palm oil and their methyl esters

Abstract

The search for a cost-effective, environmentally friendly and sustainable feedstock for biodiesel production has attracted attention among researchers. After frying, palm oil may become thermally degraded and unsuitable for consumption. In the current effort, neat palm oil (NPO), waste palm oil earlier utilized for frying fish and chips (WPOFC) and waste palm oil previously utilized to fry sausage and chips (WPOSC) were transesterified into waste palm oil methyl ester, namely, WPOMEFC and WPOMESC, respectively. The PO, WPOs and their ester derivatives were subjected to physicochemical properties, fatty acid (FA) compositions and1H and13C nuclear magnetic resonance (NMR) analyses. The thermal degradation, transesterification process and the foods the palm oil was used to fry affected the density, kinematic viscosity, acid value, pH, iodine value and FA profile of the samples. The outcome of the characterization reveals that the1H and13C NMR spectra of NPO, WPOFC and WPOSC show clear similarity, but NPO exhibits different intensities from that of the WPO samples. The absence of the peaks between δ 4.6 ppm and 5.0 ppm in the1H NMR spectrum signifies the complete transformation of triglycerides in the WPO samples into biodiesel. The13C NMR spectrum indicates the presence of ester carbonyl carbon (C=O) in WPOMEFC and WPOMESC, peculiar to ester, at a chemical shift ranging from 174.8 ppm to 174.9 ppm.