Quality and anti-adulteration control of vegetable oils through microwave dielectric spectroscopy

Quality control of vegetable oils is becoming more stringent, and strict laws are being enforced, especially for avoiding adulteration. The public bodies that are responsible for the prevention of the adulteration of foodstuffs necessitate methods of analysis that could facilitate large-scale in situ controls. Similarly, oil producers constantly strive to speed up internal quality control. As a direct consequence, there is an increasing demand for innovative methods of analysis that could guarantee real-time in situ monitoring and provide adequate accuracy. On such bases, the present work addresses the possibility of monitoring qualitative characteristics of vegetable oils through microwave dielectric spectroscopy. To this purpose, the Cole–Cole dielectric parameters of different vegetable oils are evaluated through an innovative automatable procedure that suitably combines traditional TDR measurements, SOL calibration, frequency domain processing, TL modelling and, finally, a minimization routine. The proposed procedure is carried out first on different “pure” oils and, secondly, on some oil mixtures. The obtained results confirm that different dielectric characteristics are associated with different oils, thus confirming the considerable potential of dielectric spectroscopy for quality and anti-adulteration control purposes, especially in view of practical applications.