Percorrer por autor "Seiquer, Isabel"
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- Application of a potentiometric electronic tongue for assessing phenolic and volatile profiles of Arbequina extra virgin olive oilsPublication . Borges, Thays H.; Peres, António M.; Dias, L.G.; Seiquer, Isabel; Pereira, J.A.The capability of determining the phenolic and volatile profiles of olive oils is of major relevance since these compounds are known to greatly influence the gustatory and olfactory positive attributes of olive oils. An electronic tongue with multiple linear regression models was used to evaluate both profiles based on olive oils potentiometric data generated during a single assay. The proposed electronic tongue-chemometric procedure enabled the quantification of flavonoids, phenolic acids and phenol alcohols of Arbequina extra-virgin olive oils with a similar accuracy of UPLC-MS (0.93 ± 0.03≤R2≤0.98 ± 0.08 for the repeated K-fold cross-validation procedure). Also, it was verified that the potentiometric device should not be applied to evaluate volatile compounds in solution (0.80 ± 0.14≤R2≤0.94 ± 0.05 for the repeated K-fold cross-validation procedure), showing a lower accuracy than HS-SPME-GS-MS. The overall satisfactory results showed that electronic tongue could be used as a practical sensing instrument to generate a chemical profile of the compounds known to influence the positive sensory attributes of olive oils.
- Characterization of Arbequina virgin olive oils produced in different regions of Brazil and Spain: physicochemical properties, oxidative stability and fatty acid profilePublication . Borges, Thays H.; Pereira, J.A.; Cabrera-Vique, Carmen; Lara, Luis; Oliveira, Adelson F.; Seiquer, IsabelProduction of virgin olive oil is beginning in Brazil. This paper analyzes the characteristics of the EVOO Arbequina from Brazil in comparison with Spanish Arbequina from different regions. Quality parameters, oxidative stability, pigments, colour and fatty acid profile were assessed, and relationships with geographic and climatic conditions were studied. All the samples presented good quality and met EU standards for extra-virgin olive oil, but there were significant differences between regions and countries for many of the parameters evaluated. Major differences between Brazilian and Spanish samples were observed for free acidity and colour of the oils, as well as minor variations in the fatty acid profile. The colour differences were related to rainfall, whereas the fatty acid content was strongly influenced by altitude and temperature. These results highlight the fact that geographic area and environmental factors influence the characteristics of Arbequina oil and play an important role in newly introduced cultivars.
- Comparative analysis of minor bioactive constituents (CoQ10, tocopherols and phenolic compounds) in Arbequina extra virgin olive oils from Brazil and SpainPublication . Borges, Thays H.; López, Luis Carlos; Pereira, J.A.; Cabrera-Vique, Carmen; Seiquer, IsabelThere is currently an emerging production of olive oil in Brazil but it is still poorly characterized. In this study, we performed a comparative analysis of minor bioactive constituents (CoQ 10 tocopherols and phenolic compounds) in extra virgin olive oil from different regions of Brazil and Spain, of Arbequina cultivar. Significant variations (P < 0.05) in the concentration of the compounds analyzed were observed among oils from the different growing areas, not only between Spanish and Brazilian samples but also within zones of the same country. All the oils analyzed showed a high content of CoQ 10 , which ranged from 48 to 85 mg/L. The α − tocopherol was the major isomer quantified and three main groups of phenolic compounds were identified: flavonoids (apigenin, luteolin), phenolic acids (naringenin, p-coumaric acid, vanillic acid) and phenolic alcohols (hydroxytyrosol). Climatic and geographic factors of the production zones greatly influenced the minor fraction composition; positive relationships between altitude and the level of CoQ 10 , tocopherols and phenolic compounds of the oils were observed, whereas a negative correlation with rainfalls was found. Chemometric analyses demonstrated that oils were differentiated by the chemical composition and origin area and that polyphenols (particularly hydroxytyrosol) held the major weight in the oil classification.
- Study of the antioxidant potential of Arbequina extra virgin olive oils from Brazil and Spain applying combined models of simulated digestion and cell culture markersPublication . Borges, Thays H.; Pereira, J.A.; Cabrera-Vique, Carmen; Seiquer, IsabelA physiological approach to assessing the antioxidant potential of Arbequina EVOO from different zones of Brazil and Spain was performed, applying a combined model of simulated digestion and cell cultures, using the Caco-2 cell line. Our results showed an increasing of total phenolic content (TPC) and antioxidant properties promoted by the in vitro digestion. Preincubating Caco-2 cells with bioaccessible fractions of oils counteracted the cytotoxic effect promoted by an oxidising agent (t-BOOH), preserving cell viability and reducing the generation of reactive oxygen species (ROS). The protective effect on ROS production was associated with the antioxidant activity (DPPH assay), but no relation with the TPC of the digested samples was found. Differences in the parameters evaluated were observed among the samples, which were related to climatic characteristics of the production zones. It was concluded that transformations during the digestive process are important for establishing the antioxidant potential of the oils.
- Use of response surface methodology (RSM) for the identification of the best extraction conditions for headspace solid-phase micro extraction (HS-SPME) of the volatile profile of cv. Arbequina extra-virgin olive oilPublication . Borges, Thays H.; Ramalhosa, Elsa; Seiquer, Isabel; Pereira, J.A.The effect of the experimental conditions on assessing the global volatile profile of extra virgin olive oils (EVOO) by headspace solid-phase microextraction/gas chromatography-mass spectrometry (HS-SPME/GC–MS) is studied to obtain maximization of the total peak areas of the compounds. Response Surface Methodology (RSM) is applied to Arbequina EVOO, and the influence of oil quantity, extraction time, and extraction temperature on the total area and extraction of the major desirable compounds is analyzed. The experimental data are adequately fitted into second-order polynomial models with non-significant lack of fit (p>0.05) and coefficients of determination (R2 and R2-adjusted) higher than 0.88 and 0.78, respectively. A strong similarity is found between the predicted and experimental values. Furthermore, the surface plots show that the extraction of the volatile compounds is favored with increasing extraction temperature, time, and oil quantity. The extraction conditions to obtain the maximum response of “green” volatile compounds from Arbequina olive oil by HS-SPME placed in 50 mL vials are 4.6 g of oil, 43 min, and 59 ºC. Practical Applications: The findings of the present work show that specific conditions of HS-SPME/GC–MS affect the extraction of volatile compounds from cv. Arbequina olive oil and establish the optimum extraction parameters to more efficiently determine the global profile of this fraction, taking into account the organoleptic characteristics of the cultivar. The results also contribute to the knowledge of the volatile profile of the monovarietal olive oil cv. Arbequina, which is one of most cultivated and consumed types of olive oil worldwide.