Application of a simplified calorimetric assay for the evaluation of extra virgin olive oil quality

Abstract

Thermal properties of eighteen monovarietal extra virgin olive oils from the Apulia region in Italy were evaluated by means of a modulated adiabatic scanning calorimeter (MASC) and related to their chemical composition (free acidity, UV absorbance, fatty acid composition, polyphenol and o-diphenol content, oxidation status). MASC was used to study oil sample phase transitions in a temperature scanning mode by using a tailor-made time–temperature protocol. Crystallization kinetics and transition enthalpies were found to be significantly correlated to single free fatty acids (palmitic, oleic and linoleic acids) and to unsaturated/saturated fatty acid ratio. The overall crystallization curves were significantly delayed and occurred over longer time ranges as a function of higher peroxide index and linoleic acid content. Significant correlations were observed between melting profiles and single fatty acids, unsaturated/saturated fatty acid ratio and oleic/linoleic acid ratio. No significant correlations were observed between thermal properties and free acidity, linolenic acid, polyphenol and o-diphenol content.Compared with classical differential scanning calorimetry, MASC was simpler to use. The applied time–temperature protocol allowed the characterization of extra virgin olive oils (EVOOs) of different provenience with rapid measurements and giving rise to friendly outcome data. MASC, with its compact and portable equipment, may promote practical applications of calorimetric test along the olive oil supply chain.