KEYWORDS: Olea europaea L. oil, Maçanilha Algarvia, Cobrançosa, Picual, storage, Thymbra capitata essential oil.
ABSTRACT: Varietal olive oils of Maçanilha Algarvia, Cobrançosa and Picual cvs. and a commercial virgin olive oil (Brand) were stored for 140 days at 60ºC in the dark after addition of Thymbra capitata essential oil to half of the samples. Storage had no effect on the fatty acid profile analyzed by gas chromatography and gas chromatography coupled to mass spectrometry. Acidity substantially increased during the first 51 days of storage. Peroxide index and p-anisidine value increased over time. --Tocopherol analyzed by high performance liquid chromatography decreased over time. There were significant differences between the olive cultivars in lipid peroxidation, with the commercial Brand showing the greatest peroxide values in non aromatised and aromatised olive oils. Generally, peroxidation was greater in aromatized olive oils, with the exceptions at days 0 and 140. The remaining parameters were not significantly different between non- and aromatized olive oils.
Olive oil, obtained from the fruit of the olive tree (Olea europaea L.), is mainly produced in countries surrounding the Mediterranean Sea (1). This region provides 97% of the total olive production of the world, primarily in Italy and Spain (2).
Olive oil quality is based on parameters that include free fatty acid concentration, peroxide value, UV specific extinction coefficients and sensory score (3,4). Commercial olive oils are separated in two groups, those obtained from the olive fruit solely by mechanical or physical means (olive virgin oil) and those that also contain refined olive oil (5).
The olive oil quality can be influenced by the cultivar, environmental and cultural conditions during fruit growing (mineral nutrition, ambient temperature, light, water availability) fruit processing for oil extraction, and olive fruit and oil sanitary condition and storage (6,7). Thus, oil quality may change over time and location (5). In addition, olive oil quality depends on market preferences and is based upon consumer perceptions of aroma, taste and colour.
Generally, olive oil is particularly resistant to storage and more suitable for cooking than other vegetable oils mainly due to the high proportion of monounsaturated fatty acids (oleic acid), low concentration of polyunsaturated fatty acids, and the existence of natural antioxidants (8). Nevertheless, factors such as oxygen, light, temperature and metals, are responsible for the deterioration of the olive oil quality during storage as a consequence of oxidative and hydrolytic degradations (9). Some essential oils extracted from aromatic plants were found to act as antioxidants, preventing and delaying oxidative processes. Thymbra capitata is an aromatic plant with carvacrol as the main component in the essential oil that demonstrated a good capacity for preventing lipid oxidation in samples with olive oil (10).
To verify olive oil characteristics, chemical and sensorial analyses can be used, including comparison of aroma compounds, oxidative stability, phenolic compounds, colour and other chemical parameters (7).
Cobrançosa is one of the most important Portuguese olive cultivars (6,7) and Maçanilha Algarvia the main cultivar...