DSC characterization of different olive oil categories

The EC Council of Regulation (Regulation (EC) No 1513/2001) have recently redefined commercial categories of olive oil and olive-pomace oil to avoid misleading of consumers and operators and to preserve high-quality products. DSC has proven to be able to differentiate monovarietal extra virgin olive oil and good correlation between thermal properties and chemical composition has been reported. The aim of this work was to characterize different commercial olive oils by means of DSC cooling and heating thermograms. Samples of extra virgin olive oil, refined olive oil, olive oil, refined olive-pomace oil and olive-pomace oil were analyzed by means of DSC (DSC Q100, TA Instruments, New Castle, DE). All samples were cooled from 30 to -80°C at 2°C/min, held at -80°C and heated from -80 to 30°C at 2°C/min. Enthalpy (H, J/g), onset (Ton), and offset (Toff) temperatures, as well as range of transitions, were obtained. Crystallization profiles of all samples showed two well defined exothermic events, a minor one at about -15°C and a major one at about -39°C. Crystallization of pomace oils had significantly lower enthalpy that the other samples, starting at higher temperature and developing over a larger range of temperature. Heating profiles exhibited more marked differences. Two well defined endothermic events were observed at about -6 and 7°C. Lineshapes of the melting event peaking at higher temperature, were found to be different for the various olive oil categories. An additional endothermic peak at lower temperature was found in the refined olive oil, while the other oils exhibited an exothermic event which was more pronounced in pomace samples. Both refined oils displayed higher melting enthalpy and larger range of transition than their corresponding blends with virgin oil.