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- Aromatized olive oils: Influence of flavouring in quality, composition, stability, antioxidants, and antiradical potentialPublication . Sousa, Anabela; Casal, Susana; Malheiro, Ricardo; Lamas, Hugo; Bento, Albino; Pereira, J.A.In the present work different flavourings (garlic, hot chili peppers, laurel, oregano and pepper) commonly used in Mediterranean cuisine were added to olive oils from Cv. Cobrançosa. Flavouring influence in olive oils quality, fatty acids profile, tocopherols and tocotrienols composition, antiradical activity, total phenols content and oxidative stability were evaluated. Garlic addition induced an increase in free acidity values (from 0.6 to 0.8%), but the remaining quality indices weren't negatively affected. Fatty acids profile changed but values remained under the limits of extra-virgin olive oils. Olive oils were nutritionally enriched due to the increase in vitamin E, mainly in oils flavoured with hot chili pepper (198.6 mg/kg). Antioxidant properties were influenced as well. Total phenols content decreased in all flavoured olive oils (control with 345.7 mg CAE/kg; oregano 293.8 mg CAE/kg) but the capability to counteract oxidation was generally improved (control with 9.4 h and oregano with 10.4 h). The addition of flavouring influenced quality, composition and olive oils characteristics being possible to separate them according to the flavouring used by applying chemometrics.
- Olive oil stability under deep-frying conditionsPublication . Casal, Susana; Malheiro, Ricardo; Sendas, A.; Oliveira, Beatriz; Pereira, J.A.The suitability of different commercial olive oil categories for domestic frying was investigated. Oil samples were taken every 3 h of frying and evaluated for free acidity, peroxide and p-anisidine values, specific extinction coefficients, oxidative stability, fatty acids, vitamin E, b-carotene and total phenols, until the total polar compounds achieved the maximum legal value (25%). All olive oils were fried during more time than the commercial vegetable oil blend taken for comparison (from 24 to 27 h, against 15 h). The extra-virgin Protected Designation of Origin (PDO) olive oil was characterized by reduced levels of oxidation and hydrolysis, and superior amounts of minor antioxidant compounds. The ‘‘olive oil” commercial category behaves similarly, but ‘‘Cobrançosa” olive oils performance was slightly worse, and clearly different between years, highlighting the importance of blending different cultivars. The vegetable oil, despite containing significantly higher amounts of vitamin E, was highly susceptible to oxidation under frying conditions when compared to all olive oils. The results also show that the chemical composition of olive oils, particularly the amount of natural antioxidants, are important parameters in their predictive behavior along the frying process, but mostly that olive oil is clearly resistant to frying conditions, independently to the commercial category chosen.
- Effect of cultivar on sensory characteristics, chemical composition, and nutritional value of stoned green table olivesPublication . Malheiro, Ricardo; Casal, Susana; Sousa, Anabela; Pinho, P. Guedes de; Peres, António M.; Dias, L.G.; Bento, Albino; Pereira, J.A.The effect of olive cultivar on sensory characteristics, chemical composition, and nutritional value of traditional stoned green table olives “alcaparras” was studied. The most representative cultivars from Trás-os-Montes region, Portugal (Cv. Cobrançosa, Madural, Negrinha de Freixo, Santulhana, and Verdeal Transmontana) were studied. The results showed that, regardless the cultivar, water was the main constituent with values greater than 70%, followed by fat that varied between 12.5% and 20.1%. Carbohydrates amount was greater in Cv. Madural (9.2%) and those produced from Cv. Cobrançosa had higher level of nitrogenous compounds, with 1.4%. Ashes contents of table olives varied from 1.6% to 1.9%, without significant differences among cultivars. Moreover, 100 g of “alcaparras” provided an energetic value between 154 and 212 kcal for Cv. Madural and Verdeal Transmontana, respectively. Oleic acid was the main fatty acid detected (higher than 66.9%), followed by palmitic acid (10.8–13.3%) and linoleic acid (2.7–10.3%). A linear discriminant model was established based on the “alcaparras” table olives fatty acids profile. Three fatty acids (C16:0, C18:0, and C18:3) and total saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids contents allowed distinguishing between the five olive cultivars studied, with overall sensitivity and specificity of 100%. The total content of vitamin E of the table olives varied from 3.5 and 6.0 mg/kg (for Cv. Santulhana and Negrinha de Freixo, respectively), being α-tocopherol the most abundant. The consumer’s panel showed higher preference for the table olives of Cv. Verdeal Transmontana and Negrinha de Freixo, while Cv. Madural was negatively characterized in all the descriptors evaluated. Keywords Olea europaea L. . Stoned table olives.
- Chemometrics as a tool to discriminate geographical origin of Cyperus esculentus L. based on chemical compositionPublication . Lopéz-Cortés, Isabel; Salazar-García, Domingo C.; Malheiro, Ricardo; Guardiola, Vicente; Pereira, J.A.tIn the present study the chemical composition of Cyperus esculentus L. (tiger nut) from four distinctgeographical origin (Spain, Egypt, Nigeria, and South Africa) was assessed to observe the possible effect ofthe cultivation site in the fatty acids profile, sterols composition, and squalene and -tocopherol content.It was verified that the individual fatty acids as well as the different fatty acids fractions were severelyaffected by the geographical origin. Tiger nut oils were predominantly monounsaturated with lowerprevalence of saturated fatty acids, and with capability to provide appreciable amounts of essential fattyacids. The sterols fraction was affected as well, but in lower extent. -sitosterol was the most abundantsterol found, reaching nearly 60% of the total sterols found in tiger nut oils, with significant differencesamong geographical origins.The fatty acids data, together with the sterols and -tocopherol and squalene data were capable toseparate tiger nut samples according to their chemical composition and geographical origin when a prin-cipal component analysis was applied. The fatty acids profile could be applied as a possible geographicalauthenticity marker.
- Chemical characterization of “Alcaparras” stoned table olives from Northeast PortugalPublication . Sousa, Anabela; Casal, Susana; Bento, Albino; Malheiro, Ricardo; Oliveira, Beatriz; Pereira, J.A.Commercial stoned table olives named "alcaparras" from Trás-os-Montes (Portugal) were chemically characterized. During three consecutive years (2004-2006) 30 samples (10 per year) were examined for their nutritional value (moisture, crude protein, total fat, ash, carbohydrates, and energy), with a detailed report of the fatty acids and tocopherols composition. Water was the major constituent (72.5 ± 5.5%), followed by fat (14.6 ± 5.1%). The average amount of protein and ash were 1.1% and 3.4%, respectively, reporting unusual ash values for table olives, related to the technological process. One hundred grams of fresh stoned table olives presented an average energetic value of 156 kcal, lower than most table olives. The lipids are rich in oleic acid (average of 77.7 ± 2.0%), followed by palmitic acid and linoleic acid. Samples showed an average of total tocopherols of 1.2 mg/100 g of fresh weight, being α-tocopherol the most abundant. Table olives are important sources of MUFA, as olive oil, recognized as a preventive factor in diseases in which free radicals are implicated, complemented by the amounts of vitamin E, with both antioxidant and vitamin action.
- Influence of strawberry tree (Arbutus unedo L.) fruit ripening stage on chemical composition and antioxidant activityPublication . Oliveira, Ivo; Baptista, Paula; Malheiro, Ricardo; Casal, Susana; Bento, Albino; Pereira, J.A.Arbutus unedo is a widespread shrub with economic importance, derived from the use of its berries in the production of alcoholic beverages and in folk medicine. This work intends to evaluate for the first time the effect of fruit ripening stage on antioxidant activity, total phenolic content, fatty acid profile and tocopherol composition. Ripe fruits shown higher extraction yield (45.04±2.23%) when compared to other fruit ripening stages. By contrast, total phenol contents were higher in the unripe and intermediate stage of ripeness (108 and 111 mg GAES/g dry fruit, respectively, against 60 mg/g dry fruit when ripe). Ripe and intermediate fruits shown the lower EC50 values on the DPPH radicals (0.25±0.02 mg/mL) and reducing power assay (1.09± 0.05 mg/mL), respectively. A significant correlation was established between antioxidant activity and fruits ripening stage. Fatty acid profiles were very similar between the ripening stages, being alfa-linolenic, linoleic and oleic, the three major ones. Polyunsaturated fatty acids (PUFA) represent as much as 60% of the total fatty acids, with a highly favorable omega 3/omega 6 ratio. From the analysis of the vitamin E vitamers, the most important was γ-tocotrienol, with a clear reduction in the total free vitamin E content with ripening. These results highlight that the fruits of intermediate ripeness can be regarded important sources of biologically active compounds with a fatty acid profile rich in omega-3 PUFA, properly supplemented with high vitamin E amounts.