Reference materials for supporting sensory panel tests

OLEUM partners are working on the improvement of sensory panel tests for assessing virgin olive oil quality. One of the strategies to address this improvement is the development of reference materials that can be used for the training of panellists.

The reference materials that are currently used in virgin olive oil sensory assessment are natural virgin olive oils qualified with different defects; e.g., fusty-muddy sediment, musty-humid, winey-vinegary, frostbitten olives, rancid. However, those samples may differ in the defect intensity and secondary odours from one year to another. Furthermore, it is difficult to get a reference material with a single defect that is stable over time.

Therefore, it has been proposed to prepare reference materials resembling specific sensory defects by adding single pure molecules appropriately combined in defined concentrations to an odourless oil matrix. The aim is to reproduce odours as similar to the perception of sensory defects as possible. Such reference materials, that can be easily prepared according to a validated formulation, will protect against changes in their sensory perception over the years and will help in improving the training of panellists; shared and reproducible standards will foster a better reproducibility of the results among panels.

The OLEUM partners collected samples of defective virgin oils and identified the volatile organic compounds (VOC) of those samples. VOC markers are selected for the development of reference materials. By now, the formulation of two reference materials for rancid and winey-vinegary defects are being developed within the OLEUM project.

These two reference materials were formulated and are being sent to the six OLEUM Panels for evaluating their utility to recognise the defects, for the determination of the related thresholds and of the intensity. Their stability during storage (shelf-life) will be also evaluated. If these sensory tests will provide a positive feedback, the sensory reference materials will be fully validated and then proposed to the market.

- Ramón Aparicio-Ruiz, Diego L. García González (Instituto de la Grasa-CSIC), Sara Barbieri, Tullia Gallina Toschi (Università di Bologna-UNIBO)