On the use of dielectric spectroscopy for quality control of vegetable oils

Quality control of vegetable oils is becoming more stringent, and related laws are being enforced especially for avoiding adulteration. As a result, there is a substantial need for methods of analysis that could provide real-time in-situ monitoring, especially for quality control purposes during production process. In this regard, the present paper investigates the possibility of monitoring qualitative characteristics of vegetable oils through microwave dielectric spectroscopy, which is a highly versatile investigative approach. In particular, the Cole & Cole frequency-domain dielectric parameters are known to be strongly related to the compositional characteristics of various substances. This way, starting from traditional Time Domain Reflectometry measurements performed on oils, the corresponding frequency domain information is retrieved. Successively, through a minimization routine, the Cole & Cole parameters of each considered oil are extrapolated. Results show that different dielectric characteristics can be associated with different oils. It is important to point out that the characteristics of the proposed procedure can be automated and, therefore, it may represent a promising solution for practical monitoring applications.