Edgar A. Sanches

Stability of lime essential oil microparticles produced with protein-carbohydrate blends

The objective of this work was to analyze the influence of maltodextrin equivalent dextrose on the lime essential oil reconstitution, storage, release and protection properties. Four treatments were evaluated: whey protein concentrate (WPC), and blends of maltodextrin with dextrose equivalents of 5 (WM5), 10 (WM10) and 20 (WM20). The reconstitution and storage properties of the microparticles (solubility, wettability and density), water kinetics adsorption, sorption isotherms, thermogravimetric properties, controlled release and degradation kinetics of encapsulated lime essential oil were studied to measure the quality of the encapsulated materials. The results of the study indicated that the DE degree influences the characteristics of reconstitution, storage, controlled release and degradation characteristics of encapsulated bioactive compounds. The increase in dextrose equivalent improves microparticle solubility, wettability and density, mainly due to the size of the maltodextrin molecules. The adsorption kinetics and sorption isotherm curves confirmed the increase in the hygroscopicity of maltodextrins with higher degrees of polymerization. The size of the maltodextrin chains influenced the release and protection of the encapsulated lime essential oil. Finally, the maltodextrin polymerization degree can be considered a parameter that will influence the physicochemical properties of microencapsulated food.

Electrosynthesis and optical characterization of poly(p-phenylene), polypyrrole and poly(p-phenylene)-polypyrrole films

Poly(p-phenylene) (PPP), polypyrrole (PPY), and poly(p-phenylene-pyrrole) (PPP-PPY) films were electrochemically synthesized in acetronitrile by cyclic voltammetry. For comparison purposes, the films were characterized by cyclic voltammetry in a monomer-free solution, and their optical responses were also obtained in the UV-VIS range of energy after varying the applied potentials. The absorbance spectra of the PPP-PPY film exhibited bands typically seen in the spectra of the homopolymers, PPP and PPY films, but better defined, intense, and related to reversible color transitions. Although it was not possible to confirm by using infrared and Raman spectroscopy that a copolymer was in fact obtained, the presence of both monomers, pyrrole and biphenyl, in the polymerization medium turned easier the process of film formation, yielding darker, more uniform, and rougher films as it was verified by photographic images and AFM (atomic force microscopy) images.

Polypyrrole@α-Al2O3 and polypyrrole@CeO2 core-shell hybrid nanocomposites:

PPy@α-Al2O3 and PPy@CeO2 nanocomposites were synthesized free of acids by in situ polymerization and characterized by X-ray diffraction, scanning electron microscopy, differential scanning calorimetry and DC electrical conductivity measurements. X-ray diffraction pattern of Polypyrrole revealed a semi crystalline structure. The Le Bail method was performed using the X-ray diffraction pattern of polypyrrole and allowed the proposition of the unit cell parameters (P21/c, a = 9.0173 Å, b = 7.1641 Å, c = 6.4184 Å, α = 90°, β = 117.7°, γ = 90°), which is composed by a dimeric molecule disposed along the [001] direction. A cauliflower-like morphology was observed in polypyrrole, which consists of incomplete spheres forming nanoparticle clusters. Core-shell morphology was verified in the nanocomposites consisting of a thin layer of polymer reinforcement disposed over the metal oxides matrices. Differential scanning calorimetry measurements allowed verifying the hydrophobic behavior of the inorganic phase, promoting the repulsion of the internal water molecules out from the polymer phase. Then the initial decomposition temperature of the nanocomposites has become smaller. The polypyrrole electrical conductivity is lower than the nanocomposites and may be related with the absence of hydration water in nanocomposites and also to the surface conductivity due to the thin polymer layer. PPy@α-Al2O3 and PPy@CeO2 nanocomposites presented DC electrical conductivity 80% higher when compared to the as-synthesized polypyrrole. Thus, the aim of this paper was to characterize structural and morphologically the pure polypyrrole as well as the PPy@α-Al2O3 and PPy@CeO2 nanocomposites and correlate these results with the DC electrical conductivity measurements.

Non-thermal combined treatments in the processing of açai (Euterpe oleracea) juice

Quality parameters of açai juice processed with ultrasound-assisted, ozone and the combined methods were analyzed in this work. Two ultrasound energy densities (350 and 700 J·mL-1) and two ozonization times (5 and 10 min with 1.5 ppm) were analyzed for pure açai juice and 8 different treatments (22 complete factorial). To evaluate the quality parameters of the juice, physical-chemical analyzes such as pH, titratable acidity, cloud value, non-enzymatic browning, rheology, antioxidant activity (DPPH and ABTS), phenolic compounds, anthocyanins, enzymatic activity (peroxidase and polyphenol oxidase) and microbial counts (mesophilic bacteria, molds and yeasts) were conducted. The treatments with ozone were better for microbial inactivation and the ultrasound for enzymatic inactivation. In general, the use of non-thermal methods can be a good alternative for the processing of açai juice.

Recovery of α-Al2O3 from Ionizing Radiation Dosimetric Sensors

Corundum, sapphire or α-Al2O3 is an important technological material in many optical and electronic applications such as solid-state lasers, optical windows and, more recently, as a radiation detector. Landauer (Glenwood, IL, USA) accumulated large number of archived and stored Luxel™ dosemeters composed of Al2O3:C, which were subjected to a recovery process. Due to the importance of this advanced crystalline material in OSL dosimetry, a recovery process was developed based on the dosemeters calcination and Al2O3:C has been reused in manufacturing of new dosemeters. This paper does not aim to optimize the recovery process, but provides an opportunity to study the involved process parameters and to recover this valuable crystalline material from used dosemeters. To the best of our knowledge no other recovery process involving this dosimetric material was described in scientific literature. Fourier Transform Infrared Spectrometry (FTIR), Thermogravimetry/Differential Thermoanalysis (TG/DTA), Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), Optically Stimulated Luminescence (OSL) and Rietveld Refinement were used to characterize the recovered material and to check for the stability of its structural and dosimetric properties.