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- Bioactive compounds of portuguese virgin olive oils discriminate cultivar and ripening stagePublication . Peres, Maria de Fátima; Martins, Luísa; Mourato, Miguel; Vitorino, Conceição; Dias, Suzana FerreiraThe presence of different bioactive compounds in virgin olive oil affects its nutritional, oxidative and sensorial properties. Phenolic compounds are olive endogenous bioactive compounds highly susceptible to degradation. Olive endogenous oxidoreductases, mainly polyphenol oxidases (PPO) and peroxidases (POD), may play an important role on the profile of bioactive compounds in olive oil by promoting oxidation of phenolic compounds. The aim of this study was to evaluate if changes on PPO and POD activities in olive fruits from two Portuguese cultivars (Olea europaea, cv ‘Cobrançosa’ and cv ‘Galega Vulgar’) are related with the composition of their olive oils, especially phenolic compounds. Pattern recognition techniques [principal component analysis (PCA), cluster analysis(CA), and discriminant analysis (DA)] were used for multivariate data analysis. Olive oils characterized by their FA composition were grouped by cultivar. When olive oils were characterized by their phenolic composition, green pigments, and enzymatic activities in fruits, they could be discriminated by olive ripening stage. Along ripening, PPO activity was only detected in the fruit mesocarp of both cultivars and POD activity was mainly detected in the seeds. The POD activity, as well as vanillin and gamma-tocopherol contents in olive oil increased with the ripening index. Conversely, higher PPO activity in fruits at early ripening stages together with higher levels of total phenols, green pigments, betatocopherol, hydroxytyrosol and p-coumaric acid in olive oils were observed. The ripening stage of fruits showed to be a key factor on the amount and profile of bioactive compounds of olive oil.
- Influence of enzymes and technology on virgin olive oil compositionPublication . Peres, Maria de Fátima; Martins, Luísa; Dias, Suzana FerreiraThis work aims at presenting the state-of-the-art about the influence of the activity of olive endogenous enzymes, as well as of the application of adjuvants in olive oil technology, discussing their influence on the composition of virgin olive oil, especially in phenols and volatile compounds.
- Co-processed olive oils with Thymus mastichina L.: New product optimizationPublication . Peres, Maria de Fátima; Roldão, Marta; Mourato, Miguel; Martins, Luísa; Dias, Suzana FerreiraOlive co-processing consists of the addition of ingredients either in the mill or in the malaxator. This technique allows selecting the type of olives, the ingredients with the greatest flavoring and bioactive potential, and the technological extraction conditions. A new product—a gourmet flavored oil—was developed by co-processing olives with Thymus mastichina L. The trials were performed using overripe fruits with low aroma potential (cv. ‘Galega Vulgar’; ripening index 6.4). Experimental conditions were dictated by a central composite rotatable design (CCRD) as a function of thyme (0.4−4.6%, w/w) and water (8.3−19.7%, w/w) contents used in malaxation. A flavored oil was also obtained by adding 2.5% thyme during milling, followed by 14% water addition in the malaxator (central point conditions of CCRD). The chemical characterization of the raw materials, as well as the analysis of the flavored and unflavored oils, were performed (chemical quality criteria, sensory analysis, major fatty acid composition, and phenolic compounds). Considering chemical quality criteria, the flavored oils have the characteristics of “Virgin Olive Oil” (VOO), but they cannot have this classification due to legislation issues. Flavored oils obtained under optimized co-processing conditions (thyme concentrations > 3.5−4.0% and water contents varying from 14 to 18%) presented higher phenolic contents and biologic value than the non-flavored VOO. In flavored oils, thyme flavor was detected with high intensity, while the defect of “wet wood”, perceived in VOO, was not detected. The flavored oil, obtained by T. mastichina addition in the mill, showed higher oxidative stability (19.03 h) than the VOO and the co-processed oil with thyme addition in the malaxator (14.07 h), even after six-month storage in the dark (16.6 vs. 10.3 h).
- Changes in virgin olive oil antioxidants, polyphenol oxidase and peroxidase activities during fruit ripeningPublication . Peres, Maria de Fátima; Martins, Luísa; Mourato, Miguel; Dias, Suzana FerreiraOne of the current challenges in olive oil quality is to assure that olive antioxidante compounds are preserved in order to maintain their role on oxidative degradation protection. (...)