Evaluation of Olive Oil Quality Grade using a Portable Battery-Operated Sensor System

Olive oil quality is normally assessed by chemical analysis as well as sensory analysis to detect the presence of organoleptic defects. Two of the most important parameters that define the quality of olive oil are the free acidity and the peroxide index. These chemical parameters are usually determinated by manual titration procedures that must be carried out in a laboratory by trained personnel. In this paper, a portable sensor system to evaluate the quality grade of olive oil is presented. The system is battery operated and is characterized by small dimensions, light weight and quick measurement response. The working principle is based on the measurement of the electrical conductance of an emulsion between an hydro-alcoholic solution and the olive oil sample. Tests have been carried out on a set of 17 olive oil samples. The results have shown how for fresh olive oil samples, the olive oil free acidity can be estimated from the electrical conductance of the emulsion. In the case of oxidized olive oil, the measured electrical conductance is also function of the oxidation level and a conductance threshold can be set to discriminate extra virgin olive oils from lower quality grade oils. The proposed system can be a low-cost alternative to standard laboratory analysis to evaluate the quality grade of olive oil.