Analysis of single-cultivar extra virgin olive oil using cyclic voltammetry

Abstract

Extra virgin olive oils (EVOO) quality evaluation is a complex task. The development of fast, simple and low-cost electrochemical methods to assess the quality of high-valued EVOOs, namely of "single-cultivar" EVOOs, which are very appreciated by consumers, is still a challenge task. Few works can be found in the literature regarding the application of sensor devices for classifying "single-cultivar" EVOOs according to the olive cultivar, in order to guarantee their authenticity. Cimato et al. [1] used the signals recorded with an electronic nose to separate among clusters of 12 different single-cultivar EVOOs. Apetrei et al. [2] showed that combining the electrochemical signal data obtained from electronic eye, nose and tongue allowed a good predictive classification capacity according to the olive variety of three single-cultivar EVOOs, with different degree of bitterness. In this work an approach based on cyclic voltammetry (CV) is proposed to analyze 4 different single-cultivar EVOOs (1 Portuguese (pt) and 3 Spanish (es) cultivars): Cobran~osa (C-pt), Manzanilla (M-es), Frantoto (F-es) and Redondilha (R-es). For each EVOO sample, 3 extractions were performed using a solution of ethanol/water (EtCH/H 20 1:4; v:v). The CV technique has been evaluated using an Ag/AgCI double-junction reference electrode (M90-02, Orion) and two pairs of counter/working electrodes: (i) platinum (M241Pt, Radiometer) and silver (M295Ag, Radiometer) electrodes or (ii) two platinum (M241Pt and M21, Radiometer) electrodes. The resultant currents of the potentiostat-galvanostat device (PG580, Uniscan) have been acquired between -1.5 to +0.8 V (Pt/Ag) or -2 to +2V (Pt/Pt), at a potential scan rate of 100 mV /s (UiEChem v.1.34 software, Unisann Instruments Ltd) and considered for data analysis. The preliminary results, allow expecting that, the differences of shape and pOSition of the peaks from the CV, observed from one extract to another, can be used to differentiate between single-cultivar EVOOs, according to cultivar and/or geographical origin.