Browsing by Author "Pedro, Luis G."
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- Mineral and volatile composition of agua-mel from PortugalPublication . Miguel, Maria Graça; AAZZA, Smail; Antunes, Maria Dulce; Faleiro, Maria Leonor; Barroso, José G.; Pedro, Luis G.; Figueiredo, A. CristinaAgua-mel (honey-water) is a typical honey-based product produced by the Portuguese beekeepers, particularly in southern Portugal. Agua-mel was characterized by mineral content and volatiles contents. Mineral content evaluation was performed based on a random sampling of 14 samples from a total of 16 samples provided by local producers. Mineral content showed that potassium predominated in agua-mel samples (1270-4105 mg/kg). The concentration of aluminium in one sample was tenfold higher (5.8 mg/kg) than in the remaining samples (0.3-0.6 mg/kg). Agua-mel volatiles were isolated by hydrodistillation and analysed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) from a subset of eight samples. Cluster analysis showed two poorly correlated clusters (S (corr) < 0.3). Cluster I only sample was dominated by trans-beta-ocimene (19 %), gamma-terpinene (15 %) and 2-furfural (9 %). Cluster II that included the remaining seven samples showed two moderately correlated subclusters (S (corr) < 0.5). The six samples with high correlation from subcluster IIa were dominated by 2-furfural (18-41 %) and benzene acetaldehyde (12-39 %). n-Nonadecane (14 %), n-heneicosane and 2-furfural (both 13 %) were the main components of subcluster IIb sample. Although the presence of some volatile compounds can help in the correlation between agua-mel and honey botanical source, the final product varies largely according to the preparation process even for the same producer, in different years. Agua-mel detailed characterization may assist in bringing added value to this typical Portuguese honey-based product.
- Stability of fried olive and sunflower oils enriched with thyrnbra capitata essential oilPublication . Miguel, Maria; Antunes, Maria Dulce; Rohaim, Abdulrahman; Figueired, Ana Cristina; Pedro, Luis G.; Barroso, Jose G.The stability of olive and sunflower oils for domestic uses after frying cow steak or only heating were evaluated in the presence or absence of the carvacrol-rich essential oil of Thymbra capitata. The treatments consisted of sunflower and olive oils either enriched with 200 mg/l of T capitata oil or without it, heating at 180 degrees C for 20 min, or frying 100 g cow steak at the same temperature and for the same period of time. In all assays, acid, peroxide, and p-anisidine values were followed over time. The fatty acid profile was estimated before heating or frying as well as at the end of the experiment. The results showed that the type of fat as well as the type of treatment (frying or heating) was determinant for the acid, peroxide, and p-anisidine values found. The presence of the essential oil also demonstrated to affect those values depending on the type of the oil as well as on the type of the treatment (frying or heating). In contrast, the fatty acid profile did not change greatly.
- Thymus camosus Boiss.: effect of harvesting period, collection site and type of plant material on essential oil compositionPublication . Miguel, Maria Graça; Duarte, João; Figueiredo, A. C.; Barroso, Jorge G.; Pedro, Luis G.The essential oils, isolated by hydrodistillation, from the flowers and the remaining aerial parts (leaves plus stems) from three populations of Thymus carnosus Boiss., collected at different harvesting periods and in three collection sites of Portugal (QL, LM and LA) were analyzed by GC and GUMS. The oil yields from the flowers collected in LA, QL and LM were six, four and one-fold higher, respectively, than the average oil yields from the remaining aerial parts. Monoterpenes were dominant in all oils (> 86%), and sesquiterpenes accounted for 1-6% of the total oils. Diterpenes, phenylpropanoids and non-terpenoid compounds were present in all oils (0.1-0.6%, trace amounts and t-0.4%, respectively). Borneol (26-31%) andcamphene (9-18%) dominated QL oils and borneol (18-23%), terpinen-4-ol (11-19%) and camphene (8-10%) were the main components of LM oils. LA oils showed high variability in the dominant components, cis-sabinene hydrate (14%), terpinen-4-ol (12%) and borneol (11%) being the main components in the flower oil. Terpinen-4-ol (18%) and borneol (18%) dominated the vegetative phase oil, whereas borneol (21%) and terpinen-4-ol (16%) dominated the aerial parts oils collected in May and July, respectively. QL oils can be classified as a borneol/camphene chemotype and one of the LA samples as borneol/cis-sabinene hydrate/terpinen-4-ol chemotype. However, all the other LM and LA samples do not fit within the previously defined chemotypes.