A novel electrochemical method for olive oil acidity determination

• Electrical Impedance Spectroscopy has been used to estimate olive oil acidity.
• An emulsion between the oil and an hydro-alcoholic solution is created.
• The technique can discriminate extra-virgin olive oils from lower quality oils.
• The technique is validated on a set of 39 olive oil samples.
• The technique has been implemented in the form of a low-cost portable system.

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 standard procedures to measure acidity and peroxide index feature manual titration requiring laboratory environment and trained personnel.In this paper a novel technique, based on electrical impedance spectroscopy, is presented and implemented as a low-cost, mobile instrument to be used everywhere and by anybody, with substantial improvements of the current quality control of olive oil producers of any dimension.The presented method is validated on 39 olive oil samples with different levels of acidity, peroxide index and total phenolic content.The results show that the conductance of an emulsion of olive oil with a hydro-alcoholic solution is correlated with the oil acidity. Furthermore, since, for the same oil, the emulsion conductance varies with the oil storage conditions (because of increases in the peroxide index), the presented technique could also be used to evaluate product ageing.