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

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 (WPO_FC) and waste palm oil previously utilized to fry sausage and chips (WPO_SC) were transesterified into waste palm oil methyl ester, namely, WPOME_FC and WPOME_SC, 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, WPO_FC and WPO_SC 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 WPOME_FC and WPOME_SC, peculiar to ester, at a chemical shift ranging from 174.8 ppm to 174.9 ppm.