Rapid NIR determination of alkyl esters in virgin olive oil

J. A. Cayuela

doi:10.3989/gya.1275162

Abstract

The regulation of The European Union for olive oil and olive pomace established the limit of 35 mg·kg-1 for fatty acids ethyl ester contents in extra virgin olive oils, from grinding seasons after 2016. In this work, predictive models have been established for measuring fatty acid ethyl and methyl esters and to measure the total fatty acid alkyl esters based on near infrared spectroscopy (NIRS), and used successfully for this purpose. The correlation coefficients from the external validation exercises carried out with these predictive models ranged from 0.84 to 0.91. Different classification tests using the same models for the thresholds 35 mg·kg-1 for fatty acid ethyl esters and 75 mg·kg-1 for fatty acid alkyl esters provided success percentages from 75.0% to 95.2%.

Highlights

Virgin olive oil is the natural juice of the olive, which is usually a product of good or high quality
Time domain reflectometry (Berardinelli et al, 2013) and mid infrared spectroscopy (Valli et al, 2013), the only techniques which are rapid and without sample preparation for analyzing Fatty acid alkyl esters (FAAEs) reported previously, may be suitable according to the results reported, while the cost of the required equipment may be analogous to the case of the NIR technique
The versatility of NIR spectroscopy may make this analysis of FAAEs possible for olive oil and olive mill laboratories, when they already have instrumentation to be used for other previous applications

Summary

Introduction

Virgin olive oil is the natural juice of the olive, which is usually a product of good or high quality. After separating the solid and the aqueous phase from the olive oil, a series of sieves are needed Each of these elements, specially the decanter, is difficult to keep clean (Alba, 2013) and the presence of foam is frequent. Specially the decanter, is difficult to keep clean (Alba, 2013) and the presence of foam is frequent Under these conditions, alcoholic fermentation may produce ethanol or methanol in certain quantities, which constitutes substrates for esterification, lending sensory defects to olive oil (Gómez-Coca et al, 2012). When FAAEs reach a certain concentration, they make fermentative alteration evident (Pérez-Camino et al, 2002) For this reason, a relationship between the FAAE concentration of olive oils and their sensory classification has been proposed, and a link between the presence of large quantities of FAAEs in olive oil and its fermentative sensory defects has been proven (Gómez-Coca et al, 2012). Techniques for rapid determination of FAAEs in virgin olive oil for the early detection of sensory defects would be very useful

Methods

Results

Discussion

Conclusion