Promoting calorimetry for olive oil authentication

The aim of this paper is to promote calorimetry for olive oil authentication. It is our belief that the melting and freezing curves by DSC of olive oil and other edible oils could be correlated with quality, origin and storage history of the oil in a simple way, suitable for oil industry and market. Nucleation, crystallization kinetics and transition enthalpies of oil are indeed strongly dependent on molecular interactions, that is any change of oil acidic composition and minor components can be detected, as we have recently demonstrated. In particular, addition of low-cost oils to extra virgin olive oil (EVOO) and thermal and/or mechanical treatments (refinement, deodorization, filtration, etc.) of EVOO can be assessed by a first-sight analysis of the thermograms. Protocols to obtain reproducible DSC thermograms and experiments to understand the origin of the often-observed non-reproducibility, which prevented until now the use of calorimetry for oil authentication, are here described. An explanation of the melting curves even limited to the main features is a hard task owing to the polymorphism of the numerous triacylglycerols (TAG), the main component of the oil, the complexity of their mutual interactions and the effects of the minority components. To outline the level of this challenge we report: (i) the evidence that thermodynamic and kinetic processes overlap during heating of solid EVOOs and (ii) the melting curve of one pure TAG with its polymorphic transitions. (c) 2007 Elsevier B.V. All rights reserved.