Differential scanning calorimetric analysis of edible oils: Comparison of thermal properties and chemical composition

The thermal profiles of 17 edible oil samples from different plant origins were examined by differential scanning calorimetry (DSC). Two other confirm atory analytical techniques, namely gas-liquid chromatography (GLC) and hig h-performance liquid chromatography (HPLC), were used to determine fatty ac id (FA) and triacylglycerol (TAG) compositions. The FA and TAC compositions were used to complement the DSC data, iodine value (IV) analysis was carri ed out to measure the degree of unsaturation in these oil samples. The DSC melting and crystallization curves of the oil samples are reported. The con trasting DSC thermal curves provide a way of distinguishing among these oil samples. Generally, the oil samples with a high degree of saturation (IV < 65) showed DSC melting and crystallization profiles at higher temperature regions than the oil samples with high degree of unsaturation (IV > 65). Ea ch thermal curve was used to determine three DSC parameters, namely, onset temperature (T-o), offset temperature (T-f) and temperature range (differen ce between T-o and T-f). Reproducibility of DSC curves was evaluated based on these parameters. Satisfactory reproducibility was achieved for quantita tion of these DSC parameters. The results show that T-f of the crystallizat ion curve and T-f of the melting curve differed significantly (P < 0.01) in all oil samples. Our observations strengthen the premise that DSC is an ef ficient and accurate method for characterizing edible oils.