A novel electrochemical method for olive oil acidity determination

Olive oil is a very important product due to its nutritional value, sensory and antioxidant properties. National and international regulations define basic quality parameters (such as acidity and peroxide index) to discriminate high quality oils (extra virgin olive oil) from those of lower quality. The procedures to measure acidity and peroxide index are manual titration techniques requiring a laboratory environment and trained personnel. In this paper a novel technique, based on electrical impedance spectroscopy, is presented to be suitable for the realization of a simple, low-cost, mobile instrument allowing such measurements to be carried out everywhere and by anybody, with substantial improvements of the current quality control of oil producers of any dimension. The presented method has been validated on 39 olive oil samples, featuring different levels of acidity, peroxide index and total phenolic content. The results show that the emulsion conductance is the electrical parameter best suited to discriminate the oil acidity. Moreover, since the emulsion conductance is also affected by the oil storage conditions (i.e. peroxide index), the presented technique can also be proposed, in a second time, to evaluate product ageing.