Nilo Sérgio Medeiros Cardozo

Interactions between soy protein from water-soluble soy extract and polysaccharides in solutions with polydextrose.

This study focuses on the investigation of the interactions between polysaccharides (carrageenan and carboxymethylcellulose--CMC) and soy proteins from the water-soluble soy extract. The influence of pH (2-7) and protein-polysaccharide ratio (5:1-40:1) on the interaction between these polyelectrolytes was investigated in aqueous solutions with 10% of polydextrose and without polydextrose. The studied systems were analyzed in terms of pH-solubility profile of protein, ζ-potential, methylene blue-polysaccharide interactions, differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and confocal laser scanning microscopy. Although the mixtures of soy extract with both carrageenan and CMC showed dependency on the pH and protein-polysaccharide ratio, they did not present the same behavior. Both polysaccharides modified the pH-solubility profile of the soy protein, shifting the pH range in which the coacervate is formed to a lower pH region with the decrease of the soy extract-polysaccharide ratio. The samples also presented detectable differences regarding to ζ-potential, DSC, FTIR and microscopy analyses. The complex formation was also detected even in a pH range where both biopolymers were net-negatively charged. The changes promoted by the presence of polydextrose were mainly detected by blue-polysaccharide interactions measures and confocal microscopy.

Membrane Separation Processes for the Beer Industry: a Review and State of the Art

Beer is one of the most consumed beverages in the world, placing the brewing sector in a strategic economic position in the food industry. Beer production has a series of physical and chemical steps that are technically intensive when the production scale is increased. Although the production techniques have been improving for hundreds of years, many breweries still employ traditional techniques. The increasing consumption of beer and the competitive market have led the industry to search for alternative technologies to produce a better beer with reduced prices. Membrane separation processes are interesting alternatives that may be utilised in several steps of beer production and may replace some traditional and time-consuming techniques. The objective of this study is to summarise and present a literature survey of the membrane separation processes that are currently applied in the beer industry and those processes that have potential for future applications. The potential of microfiltration, ultrafiltration, reverse osmosis, pervaporation, and gas separation to accomplish almost all solid–liquid–gas separations in a brewery is discussed, providing a clear outline for researchers on the main aspects and developments of the beer-membrane field.

Formulation and characterization of poloxamer 407®: thermoreversible gel containing polymeric microparticles and hyaluronic acid

The influence of the composition and preparation method on the sol-gel transition temperature (Tsol-gel) and rheological response of poloxamer-based formulations was determined. Manual and more complex mechanical stirring were found to provide similar results. In addition, a linear dependence of Tsol-gel on the poloxamer content was observed in the range of concentrations analyzed, and a Poloxamer 407® concentration of 18% was selected. The addition of hyaluronic acid did not lead to significant changes in the Tsol-gel values. In contrast, the addition of microparticles caused a reduction in Tsol-gel without a significant reduction in gel strength, and pseudoplastic characteristics were observed, indicating that a thermoreversible gel was obtained with a rheology suitable for application in the treatment of burn wounds.

Viscoelastic fluid analysis in internal and in free surface flows using the software OpenFOAM

Synthetic polymer products are of great importance in several industrial sectors, such as for production of packaging, parts of appliances, electronics, cars and food processing industries. Due to the increasing demand for this kind of material, reduction of waste and increase of quality has become a key issue in polymer industry. In this sense modeling and simulation of processing operations appears as a fundamental tool, leading to better understanding of how the rheological properties of polymers affect their processability and final product quality, and reducing time and costs related to the development of processes and products. This work presents some basic results that aims to validate a developed methodology for internal viscoelastic fluid flows, which was developed in a previous work in the OpenFOAM computational fluid dynamics package and also will be showed a extension of this methodology for analysis of free surface viscoelastic fluid flows, using the VOF methodology. A classical flow phenomena used in the rheology literature to present the concept of viscoelastic effects was simulated, i.e., the die swell experiment. The results obtained using Giesekus model showed the great potential of the developed formulation, once phenomena observed experimentally were reproduced in the simulations.

Viscoelastic Flow Simulation: Development of a Methodology of Analysis Using the Software OpenFOAM and Differential Constitutive Equations

Abstract Viscoelastic fluids are of great importance in many industrial sectors, such as in food and synthetic polymers industries. The rheological response of viscoelastic fluids is quite complex, including combination of viscous and elastic effects and highly nonlinear viscous and elastic phenomena. This work presents a new Computational Fluid Dynamics (CFD) tool for the simulation of viscoelastic fluid flows, which consists of a viscoelastic fluid module to be used with OpenFOAM CFD package. The main reasons for using OpenFOAM in the development of this tool are its characteristics with relation to flexibility to deal with complex geometries, unstructured and non orthogonal meshes, moving meshes, large variety of interpolation schemes and solvers for the linear discretized system, and the possibility of data processing parallelization. Several constitutive equations, such as Maxwell, UCM, Oldroyd-B, Giesekus, Phan-Thien-Tanner (PTT), Finitely Extensible Nonlinear Elastic (FENE-P and FENE-CR) and some derivations of Pom-Pom were implemented, in single and multimode form, and in this work the results are presented with the Giesekus model. The proposed methodology was validated by comparing its predictions with experimental and numerical data from the literature for the analysis of a planar 4:1 contraction flow.

Composition and Performance of Styrene-Isoprene-Styrene (SIS) and Styrene-Butadiene-Styrene (SBS) Hot Melt Pressure Sensitive Adhesives

Styrenic block copolymers are widely used in HMPSA formulations, with tackifier resins and oil plasticizer. Although most commercial formulations are based on SIS, mixtures of SIS and SBS are also used to reduce cost. However, the use of SBS is restricted because it generally leads to decrease in tack. In this work, pure SIS and SBS and a SIS/SBS mixture were used in formulations with aliphatic, aromatic, aliphatic hydrogenated, and aliphatic-aromatic copolymer resins, at three different oil contents, according to a 33–1 factorial design. Interaction effects among the components were evaluated, showing a strong dependence of the HMPSA final properties on the combination of resin/rubber used. It was found that a blend of aliphatic and aromatic resins is the best tackifier for SIS, while for SBS the best choice is an aromatic-aliphatic copolymer. These results were explained in terms of specific compatibility, which was correlated to the polarizability of the material.

Influence of nutritional and physicochemical variables on PHB production from raw glycerol obtained from a Colombian biodiesel plant by a wild-type Bacillus megaterium strain

Biodegradable polymers are currently viable alternatives to traditional synthetic polymers. For instance, polyhydroxybutyrate (PHB) is intracellularly produced and accumulated by Bacillus species, among others. This study reports several wild-type Bacillus strains with the ability to accumulate PHB using raw glycerol from biodiesel production as the sole carbon source. Out of 15 strains from different sources, B. megaterium B2 was selected as the most promising strain for further statistical optimization of the medium composition. Plackett-Burman and central composite designs were used to establish key variables and optimal culture conditions for PHB production using both 250-mL shake flasks and a 7.5-L bioreactor. Temperature and concentrations of glycerol and Na2HPO4 are the experimental variables with the most significant influence on PHB production by B2. After 14 hours of fermentation in shake flasks with optimized medium, B2 produced 0.43 g/L of PHB with a 34% accumulation in the cells. In contrast, under the same conditions, a maximum PHB concentration of 1.20 g/L in the bioreactor was reached at 11 hours. These values correspond to a 48% and 314% increase in PHB production compared to the initial culture conditions. These results suggest the potential of B2 as a PHB producer using raw glycerol, which is an inexpensive, abundant and readily available carbon source.

AN ALGORITHM FOR AUTOMATIC SELECTION AND ESTIMATION OF MODEL PARAMETERS

Abstract An algorithm for automatic selection and estimation of model parameters is presented. The algorithm uses a sensitivity matrix based calculation of the parameters effects on the measured outputs and of a linear-independence metric. A predictability degradation index and a parameter correlation degradation index are used as stop criteria and the method is extended to dynamic models and multiple operating points. The applicability of the developed algorithm is illustrated through a hypothetical nonlinear input-output model and through the analysis of data from an experimental isothermal batch bioreactor. The obtained results show the effectiveness of the algorithm.

Pinhão starch and coat extract as new natural cosmetic ingredients: Topical formulation stability and sensory analysis

The objective of this study was to use pinhão derivatives, starch and coat extract, as new natural ingredients to develop cosmetic formulations. Two types of formulation, gel and emulgel, and their controls were developed. The formulations were characterized by stability studies using thermal stress. The parameters analyzed were resistance to centrifugation, pH, spreadability, rheology, content of phenolic compounds and antioxidant activity. Sensory analysis was also performed to verify the acceptability of the ingredients to potential consumers. The pH was kept the same after heating/freezing cycles for all formulations, and the formulations showed stability by resistance to centrifugation. The formulations did not induce any skin irritation or cutaneous pH alteration. The pinhão starch addition improved spreadability stability and increased viscosity when compared with control formulations. The pinhão coat extract used in these formulations is a good source of phenolic compounds and antioxidant activity. Moreover, sensory analysis indicates that the emulgel formulation is the best vehicle for adding pinhão starch and pinhão coat extract.

Phase stability analysis using a modified affine arithmetic

Abstract Phase stability analysis is a crucial step in the determination of multiphase equilibrium. This analysis by the tangent plane distance (TPD) minimization is a well-known technique, as well as the difficulties in providing guarantees that the global minimum has been found. On this regard, interval methods are powerful tools since they provide such guarantees. In this work, an interval Newton method plus generalized bisection, based on a modified affine arithmetic, is used to reliably find all possible stationary points of the TPD function. Additionally, an improved convergence test is suggested as well as a special treatment for mole fraction weighted averages. Several mixtures with up to 5 components, including LLE island type ternary systems, were studied. Both activity coefficient models and cubic equations of state were considered. For all the cases tested, the proposed modified affine arithmetic method was superior to other interval-based methods.