Tridimensional molecular assembly of the major components of extra-virgin olive oils.

A number of extra-virgin olive oils were obtained by mechanical extractions from different Sicilian olive cultivars. High field NMR analyses showed, as expected, that the major components of the extra-virgin oils were triglycerides. The measurements of the proton longitudinal relaxation times (T1) revealed that triglycerides were ellipsoidal-shaped. In fact, a multi-exponential mathematical model was applied to fit all the decay data from the classical inversion recovery experiments, thereby leading to the conclusion that anisotropic relaxation mechanisms arise into the triglycerides. Low field NMR experiments revealed two different components of the longitudinal relaxation times. The shortest T1 value was attributed to an intra-molecular spin diffusion, whereas the longest T1 was assigned to inter-molecular spin diffusion mechanisms. According to such hypothesis, it has been concluded that triglycerides in extra-virgin olive oils are assembled in contiguous supramolecular blocks. The present study showed for the first time that the combined use of different NMR techniques can be very helpful for obtaining information on the conformational assessment of natural systems such as extra-virgin oils. This is an important research issue in order to evaluate structure-activity properties of food materials which are recognised to have very relevant nutritional implications.