Development of a sensor system for vegetable oil authentication

There is an increasing interest in the classification of vegetable oils as an effective means to examine authenticity and to detect possible adulteration of extra virgin olive oils with seed oils or low-quality olive oils. Classical methods such as, Gas Chromatography, High Performance Liquid Chromatography, Fourier Transform Infrared and Nuclear Magnetic Resonance, are too expensive for widespread industrial use and require samples to be analysed in dedicated laboratories thus incurring a significant time penalty. This paper demonstrates that microwave spectrometry is able to offer real-time measurement of olive oils adequate for determining product authenticity. It does this by evaluating a sensor system used to measure the dielectric properties as against the spectrophotometric characteristics of extra virgin olive oil and other common-place edible oils. In particular, the capability of the system to distinguish between these oils, even when mixed, is demonstrated. The dilution in different range of proportions of extra virgin olive oil with a refined olive oil were tested using the IDE sensor. The VNA was set to span from 10 kHz to 15 GHz. The results are compared with spectrophotometric readings set between 650 and 700 nm wavelengths of the same samples. The analysis of the results show that there is a promising matching correlation in both methods with the R² of 0.7302 and 0.9962 for microwave spectroscopy and spectrophotometer respectively. More work is needed though to fine tune the sensor so as to achieve a higher R² value and include new designs.