Method M4C
Sensory analysis of virgin olive oil with the use of artificial reference materials
The M4C method was developed to enhance the IOC methodology for the organoleptic assessment of VOOs by the employment of novel, artificial, reproducible and stable Reference Materials (RMs), ad hoc manufactured to resemble the aroma of sensory defects, to be used for the calibration of the Sensory Panels (according to the indications listed in “Guide for the selection, training and quality control of virgin olive oil tasters-qualifications of tasters, panel leaders and trainers”). The Standard Operation Procedure (SOP) for this method was focused on the collection of feedback on the feasibility of the use of these two RMs as a support in the identification and evaluation of winey and rancid defects in VOOs, as well as on the highlighting of eventual problems and critical issues that can help to further improve the RMs.
The aims of the pre-trial for M4C were three:
i) to evaluate the representativeness of reference materials (RM1 and RM2) in terms of an assessment by the panellists of their usefulness in resembling the aroma of natural sensory defects of winey-vinegary and rancid (expressed as percentage values being possible for each assessor a binary answer useful/not useful);
ii) to calculate the perceived intensities of the winey-vinegary and rancid defects for RM1 and RM2, respectively; this determination was carried out because the definition of the intensity of each sensory RM is a fundamental information to permit its possible future use in training of assessors and panel control over time;
iii) to assess two ‘real’ virgin olive oil samples for their sensory attributes in order to use them as sensory characterized samples (training samples) in the next step of trial proper; in trial proper, these two characterized samples will be proposed to assessors to be re-analysed using in parallel the two RMs in order to establish if the provision of specific reference standards for winey and rancid can aid recognition of these attributes in samples as well as to quantify their intensities.
Ten public/private laboratories, having a trained sensory panel for olive oil analysis recognized by national/international control bodies, participated in the pre-trial. These comprised 3 from Italy, 3 from Spain, 2 from Germany, 1 from USA and 1 from Australia. The participants received two different virgin olive oil samples as well as the two RMs and were asked to analyse them following the SOP prepared by the method developers. Participants also had the opportunity to attend a knowledge transfer workshop in December 2019 in Bologna, in the course of which they asked questions and provided feedback about the application of the analytical protocol and the SOP information in particular. Participant laboratories did not report any problems or difficulties relating to the SOP, consequently, no changes were done to this document.
The high number of positive answers regarding the representativeness of the RMs suggested an agreement in the similarity with the natural aromas when these RMs were presented to diverse panels. However, considering the comments received by participant laboratories for the analysis of the RMs, as well as the results, obtained related to the median values of intensities, UNIBO and CSIC decided to select and prepare for the trial proper, mixtures of RMs to be assessed (only by olfactory) that are more diluted than those distributed during pre-trial.
The trial proper phase has been carried out in Autumn 2020.
For the Alma Mater Studiorum – University of Bologna (UNIBO): Prof. Alessandra Bendini
For the Instituto de la Grasa (CSIC): Dr. Diego Luis García González