Cv. Arbequina fruits were inoculated during one day with suspensions of Aureobasidium pullulans, Epicoccum nigrum or
both species (
104 spores/g olives), isolated from olive leaves, aiming to increase the phenolic content of the olive oils. Oils
were extracted from non-inoculated (control) and inoculated olives, being evaluated for their oxidative stability, and phenolic
composition. Compared to the control oils, those extracted from inoculated olives showed higher oxidative stability
(+ 16–29%), phenolic acids contents (up to + 37%), phenolic alcohols (up to + 101%), flavonoids (up to + 154%) and secoiridoid
derivatives (up to + 12%). These positive effects could be attributed to the hydrolytic activity of enzymes secreted by
the studied fungi on the fruit cellular membranes and extracted phenolics, increasing the extractability and, consequently,
altering the phenolic concentration. Considering the two fungi species, E. nigrum inoculation had a more significant positive
impact on the contents of tyrosol, oleuropein, and ligstroside derivatives, showing an inhibition effect regarding the
oleacein formation. Contrary, A. pullulans inoculation mainly resulted into an accentuated increase of luteolin and oleacein
contents (3 and 12-times higher compared with control oils, respectively). Overall, no enhanced positive synergetic effect
could be attributed to the inoculation with a suspension containing both fungi. The significant changes observed on the
phenolic contents, due to the fungal inoculation, allowed the successful discrimination of the four types of extracted oils
using an electronic tongue. This device acts as an artificial taste device allowing anticipating an impact at the oils’ basic
taste sensations due to the fungi inoculation.
The authors are grateful to the Foundation for Science
and Technology (FCT, Portugal) for financial support by national
funds FCT/MCTES (PIDDAC) to CIMO (UIDB/00690/2020 and U
IDP/00690/2020), CEB (UIDB/04469/2020), REQUIMTE-LAQV
(UIDB/50006/2020) units and SusTEC (LA/P/0007/2020); to Project
“GreenHealth—Digital strategies in biological assets to improve wellbeing
and promote green health” (Norte-01–0145-FEDER-000042)
and to Project AgriFood XXI (NORTE-01–0145-FEDER-000041),
funded by the European Regional Development Fund under the scope
of Norte2020 ‐ Programa Operacional Regional do Norte. Ítala M.G.
Marx acknowledges the Ph.D. grant (SFRH/BD/137283/2018) provided
by FCT. Nuno Rodrigues thanks to National funding by FCTFoundation
for Science and Technology, P.I., through the institutional
scientific employment program-contract.
