Abstract
Olive oils have been shown to be more resistant to oxidation than other vegetable fats, mainly due to their fatty acid (FA) profile which is rich in oleic acid and to their high content of antioxidants, principally phenols and tocopherols. This has situated virgin olive oils (VOOs) among the fats of high nutritional quality. However, it is important to stress that the oil’s commercial category (olive oil, virgin olive oil, extra-virgin olive oil), the variety of the source plant, and the extraction-conservation systems all decisively influence the concentration of these antioxidants and the oil’s shelf-life. The present work studied the fatty acid (FA) and phenolic composition and the oxidative stability (OS) of eight olive varieties grown in Extremadura (Arbequina, Cornicabra, Manzanilla Cacereña, Manzanilla de Sevilla, Morisca, Pico Limón, Picual, and Verdial de Badajoz), with the olives being harvested at different locations and dates. The Cornicabra, Picual, and Manzanilla Cacereña VOOs were found to have high oleic acid contents (>77.0%), while the VOOs of Morisca and Verdial de Badajoz had high linoleic acid contents (>14.5%). Regarding the phenol content, high values were found in the Cornicabra (633 mg·kg−1) and Morisca (550 mg·kg−1) VOOs, and low values in Arbequina (200 mg·kg−1). The OS was found to depend upon both the variety and the date of harvesting. It was higher in the Cornicabra and Picual oils (>55 h), and lower in those of Verdial de Badajoz (26.3 h), Arbequina (29.8 h), and Morisca (31.5 h). In relating phenols and FAs with the OS, it was observed that, while the latter, particularly the linoleic content (R = −0.710, p < 0.001, n = 135), constitute the most influential factors, the phenolic compounds, especially o-diphenols, are equally influential when the oils’ linoleic content is ≥12.5% (R = 0.674, p < 0.001, n = 47). The results show that VOOs’ resistance to oxidation depends not only on the FA or phenolic profile, but also on the interaction of these compounds within the same matrix.
Highlights
Olive oils (OOs) form the base of the Mediterranean diet
The purpose of this study was to determine how the fatty acid (FA) composition and phenolic content of extra virgin olive oil (EVOO) influence their oxidative stability (OS) in the eight main varieties grown in Extremadura (Arbequina, Cornicabra, Manzanilla Cacereña, Manzanilla de Sevilla, Morisca, Pico Limón, Picual, and Verdial de Badajoz), with the olives harvested in different locations where these varieties are more prevalent and at different harvest dates
The phenolic compound content in the virgin olive oils (VOOs) of the main olive varieties grown in Extremadura present significant differences in composition and concentration between those varieties (Table 1)
Summary
Olive oils (OOs) form the base of the Mediterranean diet. There are different commercial categories of OOs according to their quality: extra virgin olive oil (EVOO), obtained by purely physical means and with the physicochemical and sensorial parameters characteristic of healthy fruit; virgin olive oil (VOO), obtained by purely physical means but whose physicochemical and/or sensorial parameters are not those of completely healthy fruit; and olive oil, a mix of lampante olive oil that has been refined (by a chemical process to remove any negative attributes) with some proportion of VOO or EVOO. The global consumption of OOs has increased by more than 30% over the last 25 years thanks to two key aspects: their nutritional properties [1] and their sensorial properties. Their nutritional properties are provided by their fatty acid (FA) profile and high monounsaturated/saturated fatty acid ratio (MUFA/SFA), and by their antioxidant content, that of phenols which intervene in the prevention of disease [2,3]. The FA and phenol contents provide OOs with greater stability against rancidity and oxidative processes [4]. Light, temperature, metals, pigments, and the polyunsaturated fatty acid (PUFA) composition are factors that can influence autoxidation in different ways, as can the presence of antioxidants (both qualitatively and quantitatively)
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