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. 2022 Jan 21;11(2):204.
doi: 10.3390/antiox11020204.

Enrichment of Refined Olive Oils with Phenolic Extracts of Olive Leaf and Exhausted Olive Pomace

Alfonso M Vidal  1 , Manuel Moya  1   2 , Sonia Alcalá  1 , Inmaculada Romero  1   2 , Francisco Espínola  1   2
Affiliations

Enrichment of Refined Olive Oils with Phenolic Extracts of Olive Leaf and Exhausted Olive Pomace

Alfonso M Vidal et al. Antioxidants (Basel). .

Abstract

Refined olive oils (ROOs) are commonly enriched with synthetic antioxidants. Antioxidant extracts obtained from natural products can be used to improve the stability of these oils. In this study, ROOs were enriched through the addition of phenolic extracts from olive leaves (OLs) and exhausted olive pomace (EOP). In addition to replacing synthetic antioxidants with natural ones, this results in the valorization of these olive-derived biomasses. The most suitable method for mixing and enriching refined oils was probe-type ultrasonication using lecithin as the emulsifier. Thereafter, the change in the content of antioxidant compounds and the antioxidant capacity of the oils at 25, 35, and 45 °C were studied over 28 and 50 days of storage. The experimental results were fitted using a pseudo-first-order kinetic model. The oxidative stability index of the ROO enriched with a 2 g/L OL extract (70 h) was higher than that of a commercial ROO (46.8 h). Moreover, the oxidative stability index of the refined olive pomace oil (ROPO) enriched with a 2 g/L EOP extract (44.1 h) was higher than that of a commercial ROPO (38.9 h). In addition, the oxidative stabilities and antioxidant capacities of the oils were significantly correlated.

Keywords: antioxidant capacity; hydroxytyrosol; kinetic analysis; oleuropein; oxidative stability; phenolic extracts; refined olive oils.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Experimental sequence of phenolic compounds extraction and oil enrichment.
Figure 2
Figure 2
Chromatograms and characterized compounds in the concentrated extract of (a) olive leaves and (b) exhausted olive pomace.
Figure 3
Figure 3
Correlation between oxidative stability index and antioxidant capacity, determined via FRAP, of oil samples: refined olive oil (ROO) and refined olive pomace oil (ROPO).
Figure 4
Figure 4
Experimental results for (a) oleuropein content and (b) antioxidant capacity—FRAP (points) and representation of the kinetic model (lines) for refined olive oil enriched with 2% olive leaves extract.
Figure 5
Figure 5
Response surface for oleuropein kinetic model as a function of temperature and time.
Figure 6
Figure 6
Experimental result (points) for (a) hydroxytyrosol and (b) antioxidant capacity (FRAP) and representation of the kinetic model (lines) for refined olive pomace oil enriched with 2% exhausted olive pomace extract.
Figure 7
Figure 7
Response surface for hydroxytyrosol kinetic model.
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