Ultrasound assisted coextraction to obtain new olive oil preparations with ‘Cornicabra’ olives and thyme

Abstract: Flavoring virgin olive oils is a new trend in consumer preferences and different enrichment techniques are used. Co-extraction of olives with a flavoring agent can be a strategy to prevent oxidation and to obtain healthier foods. This technique allows the selection of olive type (e.g., cultivar and ripening stage), the ingredient(s) with the greatest flavoring and/or bioactive potential, as well as the extraction conditions. In the present study Thymus mastichina L. (TM), an Iberian endemism, and lemon thyme (Thymus x citriodorus) (TL) were used for flavoring Cornicabra cultivar oils by co-extraction. Thyme was added to the olives either during crushing or malaxation. Moreover, ultrasound (US) was applied before malaxation for 10 min. Quality criteria parameters, total phenols, fatty acid composition, chlorophyll pigments, phenolic profile and oxidative stability were assayed in the oils. Subsequently, the effect of storage (22-23 °C) on chemical and sensory characteristics of the oils was studied.

The obtained results showed an important sensorial improvement of all olive oil preparations obtained by co-processing, with notes of thyme (TM and TL) and lemon (TL). The phenolic profile of Cornicabra oils did not change with co-processing with ultrasound application. TM enrichment showed an improvement of several new phenolic compounds, while with TL less new phenols were observed. In the trials with TL, the extraction of chlorophyll pigments increased, particularly in crushing co-processing. The main fatty acids were within the following ranges (%): oleic acid (68.2-69.4), palmitic acid (9.5-10.2), linoleic acid (15.0-15.9) and stearic acid (2.8-2.9). After eight months storage, all the oils showed significant decrease in total phenols, especially the trials with TL co-extraction. Moreover, the trials with TM/US (in the mill or malaxation) showed less phenol decrease.

Funding: This work was funded by the research unit LEAF (UIDB/04129/2020) from Fundação para a Ciência e a Tecnologia, I.P., Portugal.