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 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. (C) 2014 Elsevier Ltd. All rights reserved.