Estimating hydroxytyrosol-tyrosol derivatives amounts in cv. Cobrançosa olive oils based on the electronic tongue analysis of olive paste extracts

Abstract

The estimation of hydroxytyrosol-tyrosol derivatives amounts in olive oils through the analysis of olive pastes collected during malaxation is of utmost relevance due to the relationship with the oils' health claim regarding the protection of blood lipids from oxidative stress. Olive pastes were collected during the industrial extraction of cv. Cobrançosa oils (060 min; 2234 °C). Total phenolic contents of pastes' extracts were assessed (28005400 mg GAE/kg paste). Oils were laboratory-extracted from each paste and, after acid hydrolysis, the contents of hydroxytyrosol and tyrosol derivatives as their sum were determined (25135, 62120 and 68255 mg/kg oil). Olive paste extracts were analyzed with a lab-made potentiometric electronic tongue. The device enabled estimating the total phenolic contents of the pastes (internal-validation: correlation coefficient 0.86, root mean square error 392 mg GAE/kg). Moreover, the electronic tongue allowed a more satisfactory indirect estimation of the total secoiridoids derivatives amounts of the oils (internal-validation: correlation coefficient 0.91, root mean square error 25 mg/kg), based on the olive pastes' potentiometric profiles, without requiring the oils posteriori invasive/destructive analysis. Thus, the electronic tongue could be foreseen as a potential tool for anticipating the health claim fulfilment during oils industrial extraction.