The use of DSC for analysis and characterization of olive oil

Olive oil is the main source of fats in the countries of the Mediterranean area, where its production is very widespread. In particular, extra virgin olive oil (EVOo) is highly appreciated for its natural flavour and aroma that are both retained as it is consumed crude without any refining process, as well as for its health and nutritional properties. Differential Scanning Calorimetry (DSC) is the most used thermo-analytical technique in the field of oil and fats research for the determination of solid fat content, crystallization and melting profiles, enthalpy of transitions and polymorphic forms. This technique also provides a reproducible method for the identification of the botanical origin of vegetable oils and for the assessment of their oxidative stability (auto- and thermo-oxidation). DSC exhibits some advantages upon the classical analytical methods as it is rapid, does not require sample preparation and use of solvents, thus resulting in a reduced environmental impact. However, literature data generally lack in information about DSC application to olive oil and, in particular, on the relation between chemical composition and thermal properties of this high quality vegetable oil. Recently, crystallization and melting profiles of monovarietal Spanish extra virgin olive oil samples and thermal properties were correlated with major components as triacylglycerol and fatty acid compositions, but the effect of minor components, which are largely present in this type of vegetable oil, on thermal properties was not considered in this work. Oxidative stability of EVOo under conventional heating treatments and the evaluation of the quality and genuineness of olive oil were investigated by DSC, but chemical composition of the oil was not taken into consideration in these studies. The authors have, therefore, decided to begin filling this gap carrying out a research program focused on thorough chemical characterization of olive oil and its relation to DCS thermal properties. The thermal properties considered were descriptive of the crystallization and/or melting of olive oil undergoing cooling and/or heating cycles. The complex lineshapes of the resulting thermograms were also deconvoluted into the constituent peaks. The results obtained were summarized in this paper.