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- Author or Editor: L. Santos x
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Abstract
This study attempted to optimize pectin extraction from queen pineapple (Qp) peels using microwave-assisted method. A three-factor factorial experimental design was employed to test the interaction of moisture content of pineapple peel, pH of the citric acid solution and extraction time. The three-way interaction among the factors has a significant effect on pectin recovery. Two-way interaction between moisture content and pH level, as well as pH level and extraction time caused significant difference in the pectin recovery. Pectin recovery increases with lower moisture content while longer extraction time does not significantly increase pectin recovery. The optimum combination of the parameters is 12% moisture content, pH level 2 of the citric acid solution, and extraction duration of 2 min, which yielded 1.01 ± 0.01% pectin recovery. This is lower than the results from previous studies on pineapple with 3.88–13.06% pectin recovery using acid extraction method. Hence further optimization is recommended.
Sunflower biodiesel
Use of P-DSC in the evaluation of antioxidant efficiency
Abstract
The higher is the degree of unsaturation in ester chain of a biodiesel, the smaller is its oxidation stability. Sunflower biodiesel obtained by the ethyl route possesses a high amount of unsaturated fatty acids, mainly oleic acid (C18:1) and linoleic acid (C18:2), thus being more prone to the oxidation process. In Brazil, with the purpose of meeting the specifications of the Brazilian National Agency of Petroleum, Natural Gas and Biofuels (ANP), antioxidant additives, from synthetic and natural origins, have been added to the biofuel. Antioxidants are an alternative to prevent the oxidative deterioration of the fatty acid derivatives, as they are substances able to reduce the oxidation rate. In this study, the oxidative stability of sunflower biodiesel, obtained by the ethyl route and additivated with different concentrations of the antioxidants butylated hydroxytoluene (BHT) and t-butylhydroquinone (TBHQ), was evaluated by means of Pressure differential scanning calorimetry (P-DSC) and the Accelerated oxidative stability test (Rancimat, Method EN 14112). The results obtained by the two techniques showed the same oxidation tendency. Thus, P-DSC can be used as an alternative to determine the oxidative stability of biodiesel. The antioxidant TBHQ, added to biodiesel at the concentrations of 2000 and 2500 mg kg−1, raised the oxidation induction time to a value higher than 6 h, the limit established by the Resolution ANP number 7/2008, thus being the best alternative among the studied antioxidants.
Abstract
The use of biodegradable natural polymers has increased due to the over-solid packaging waste. In this study, a chemical modification of the casein molecule was performed by Maillard reaction, and the modified polymer was evaluated by polyacrylamide gel electrophoresis (PAGE), thermogravimetry/derivative thermogravimetry (TG/DTG), FT-IR, and 1H-NMR spectroscopy. Subsequently, films based on the modified casein were obtained and characterized by mechanical analysis, water vapor transmission, and erosion behavior. The PAGE results suggested an increase of molecular mass of the modified polymer, and FT-IR spectroscopy data indicated inclusion of C–OH groups into this molecule. The TG/DTG curves of modified casein presented a different thermal decomposition profile compared to the individual compounds. Mechanical tests showed that the chemical modification of the casein molecules provided higher elongation rates (45.5%) to the films, suggesting higher plasticity, than the original molecules (13.4%). The modified casein films presented higher permeability (0.505 ± 0.006 μg/h mm3) than the original polymer (0.387 ± 0.006 μg/h mm3) films at 90% relative humidity (RH). In pH 1.2, modified casein films presented higher erosion rates (32.690 ± 0.692%) than casein films (19.910 ± 2.083%) after 8 h, suggesting an increased sensibility for erosion of the modified casein films in acid environment. In water (pH 7.0), the films erosion profiles were similar. Those findings indicate that the modification of molecule by Maillard reaction provided films more plastic, hydrophilic, and sensitive to erosion in acid environment, suggesting that a new polymer with changed properties was founded.
Abstract
Gypsum is a dihydrated calcium sulfate, with the composition of CaSO4⋅2H2O, with large application interest in ceramic industry, odontology, sulfuric acid production, cement, paints, etc. During calcination, a phase transformation is observed associated to the loss of water, leading to the formation of gypsum or anhydrite, which may present different phases. The identification of the phases is not so easy since their infrared spectra and their X-ray diffraction patterns are quite similar. Thus, in this work, temperature modulated differential scanning calorimetry (TMDSC) was used to identify the different gypsum phases, which can be recognized by their different profiles.
Abstract
Magnesium and zinc ferrites have been prepared by the polymeric precursor method. The organic material decomposition was studied by thermogravimetry (TG) and differential thermal analysis (DTA). The variation of crystalline phases and particle morphology with calcination temperature were investigated using X-ray diffraction (XRD) and scanning electronic microscopy (SEM), respectively. The colors of the ferrites were evaluated using colorimetry. Magnesium ferrite crystallizes above 800°C, presenting a yellow- orange color with a reflectance peak at the 600–650 nm range, while zinc ferrite crystallizes at 600°C, with a reflectance peak between 650–700 nm, corresponding to the red-brick color.
Abstract
This work presents the characterization and the kinetic compensation effect of corn biodiesel obtained by the methanol and ethanol routes. The biodiesel was characterized by physico-chemical analyses, gas chromatography, nuclear magnetic resonance and thermal analysis. The physico-chemical properties indicated that the biodiesel samples meet the specifications of the Brazilian National Agency of Petroleum, Natural Gas and Biofuels (ANP) standards. The analyses by IR and 1H NMR spectroscopy indicated the ester formation. Gas chromatography indicated that biodiesel was obtained with an ester content above 97%. The kinetic parameters were determined with three different heating rates, and it was observed that both the methanol and ethanol biodiesel obeyed the kinetic compensation effect.
