Navegando por Autor "Leles, Maria Inês Goncalves"
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- ItemEstudo da estabilidade térmica de óleos de peixes em atmosfera de nitrogênio(2004) Garcia, José Uires; Santos, Harlen Inácio dos; Fialho, Afonso Pereira; Tejerina-Garro, Francisco Leonardo; Antoniosi Filho, Nelson Roberto; Leles, Maria Inês GoncalvesThe fish are a rich source of omega 3 polyunsaturated fatty acids that give benefits to human health beyond basic nutrition. For this reason a lot of studies have been done focusing on the analysis of the content of the substances that compose the foods and the processing effects on foods. These studies have been spread to fishing resources. Many studies about thermal oxidative stability and the kinetic behavior of vegetal oils have been made by Thermogravimetry (TG), Differential Thermal Analysis (DTA) and Differential Scanning Calorimetry (DSC). However, the studies about the oil and fat (from animals) thermal behavior are still lacking. Therefore, on this research analysed the thermal stability of five fish species from Araguaia river (Goiás – Brazil) in a nitrogen atmosphere by TG/DTG. The results showed losses of mass between 235ºC and 490ºC and it points to an equivalence of thermogravimetric behavior between the oils of the five fish species and also between the fish oils and some vegetal oils, such as, araticum, Brazilian wine-palm and palm oils.
- ItemMultiresponse optimization of an extraction procedure of carnosol and rosmarinic and carnosic acids from rosemary(2016) Oliveira, Gerlon de Almeida Ribeiro; Oliveira, Anselmo Elcana de; Conceição, Edemilson Cardoso da; Leles, Maria Inês GoncalvesA green solvent-based optimization for rosmarinic acid (RA), carnosol (COH), and carnosic acid (CA) extraction, the three main antioxidants from rosemary, was performed. The conventional solid-liquid extraction was optimized using a central composite design (CCD) followed by the desirability approach. In the CCD analysis the quantitative effects of extraction time (4.8–55.2 min), liquid-to-solid ratio (4.6–21.4 mL g-¹ ), and ethanol content (44.8–95.2% v/v) were determined for the extracted amount of antioxidants, their concentrations in the extract, and the extraction yield. Samples were analyzed by HPLC and the antioxidants were identified by comparison with pure standard retention times and UV spectra. The desirability function that simultaneously maximizes the antioxidants extraction and their concentrations in the final product was validated. The extraction using a hydroalcoholic solution 70% v/v, at low liquid-to-solid ratio (5 mL g-¹), and after 55-min yielded an antioxidant recovery rate of 89.8%, and a final product 4.75 times richer in the main antioxidants than the raw material.
- ItemNb2O5 supported catalysts for cross-coupling reactions(2020) Souza, Guilherme Botelho Meireles de; Ribeiro, Thiago Soares Silva; Mourão, Lucas Clementino; Pereira, Mariana Bisinotto; Leles, Maria Inês Goncalves; Liao, Luciano Morais; Oliveira, Guilherme Roberto de; Alonso, Christian GonçalvesPalladium and nickel supported on Nb2O5 were synthesized via wet impregnation method and tested for the Suzuki-Miyaura reaction. The catalysts were characterized by X-ray fluorescence, textural analysis, scanning and transmission electron microscopy, thermogravimetry/differential thermal analysis and X-ray diffraction. Palladium catalyst resulted in high isolated yields (91%). Satisfactory yields (48%) were achieved employing the nickel catalyst. Hot filtration experiments were performed to evaluate the reaction heterogeneity. The catalysts were submitted to consecutive reactions runs to assess recyclability. Deactivation was attributed to catalyst loss by filtration between cycles, minor leaching of the active phase and poisoning by inorganic species.
- ItemSíntese, caracterização e estudo termoanalítico do ftalato, isoftalato e tereftalato de cobalto(2015-12) Carmo, João Paulo Santos do; Leles, Maria Inês Goncalves; Ionashiro, Elias Yuki