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Abstract
The chemical characteristics, phenolic content and antioxidant activity of olive oils flavored with garlic, lemon, oregano, hot pepper, and rosemary were evaluated during 9 months of storage. At the end of the storage period, the unflavored and the garlic-flavored oils maintained their chemical parameters within the limits fixed for extra-virgin olive oils. After 9 months of storage, a noticeable decrease in phenolic content was observed in all the oils. The highest (35.0 ± 3.9 mg/kg oil) and the lowest (6.3 ± 0.4 mg/kg) phenolic contents were detected in the unflavored and garlic-flavored oils, respectively. Compounds such as 3,4-DHPEA-EDA (3,4-dihydroxyphenylethyl 4-formyl3-formylmethyl-4-hexenoate, the dialdehydic form of decarboxymethyl elenolic acid linked to hydroxytyrosol) and p-HPEA-EDA (dialdehydic form of the decarboxymethyl elenolic acid linked to tyrosol) were the most abundant in both unflavored and lemon-flavored oils up till 6 months of storage. At the end of the storage period, increases in 3,4-DHPEA (hydroxytyrosol) and p-HPEA (tyrosol) were measured in almost all the oils. During storage, the antioxidant activity coefficients of the phenolic extracts, calculated according to the ß-carotene bleaching assay, significantly decreased and, after 9 months, were in a decreasing order: rosemary (51.3 ± 4.2), hot pepper, lemon, orégano, unflavored, and garlic (8.5 ± 0.7).
Keywords Antioxidant activity * ß-Carotene assay * Flavoring * Olive oil * Phenolic compounds * Quality indices * Storage
Introduction
Olive oil is widely used in the Mediterranean cuisine and is appreciated for its delicious taste and aroma, as well as for its nutritional benefits [1,2] primarily related to its balanced fatty acid composition and the presence of considerable amounts of natural antioxidants [3].
A "flavored olive oil" can be defined as an olive oil (generally extra-virgin) processed with vegetables, herbs, spices or fruits in order to improve its sensory characteristics [4]. It is possible to choose among oils flavored with vegetables (garlic, onion, pepper, chilli, sun dried tomatoes), herbs (rosemary, orégano, basil, sage, thyme, fennel, juniper, estragon), spices (clove, nutmeg, ginger), mushrooms (truffles), fruits (lemon, orange, mandarin, apple, banana), nuts (almond, hazelnut, pine nuts) and aromas (for example, oils aromatized with vanilla are used to season shellfish, poultry and salads with vegetables, fruit and shellfish).
Aromatic plants and fruits have been used throughout the ages in many fields, from food...