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Electrospun poly(vinyl alcohol)/chitosan nanofibers had their solution and process parameters optimized using a Box-Behnken design and desirability function. Four factors (applied voltage, flow rate, distance tip-to-plate and amount of chitosan) were varied to produce electrospun mats with a low fiber diameter. An empirical model was developed for each response using response surface methodology (RSM), which revealed that flow rate had no significant influence on the assessed responses. With desirability function, the optimal conditions to produce the nanofibers were applied voltage of 13.1 kV, 30% chitosan concentration and distance tip-to-plate of 10 cm. The fiber diameter and standard deviation were 196.5 ± 28.3 nm, compared to the predicted values of 185.9 ± 26.8 nm. The desirability function allied with Box-Benhken design proved themselves important tools to predict process parameters for the development of nanofibers. The mats were crosslinked with glutaraldehyde for 24 h and 48 h and presented good water stability and enhanced mechanical properties.

Arthrospira platensis is a cyanobacterium that is of great biotechnological interest, particularly for the food industry, as it possesses a high content of proteins, pigments, lipids and carbohydrates. Cyanobacteria produce extracellular polymeric substances (EPS), which are co-products of secondary metabolism that present thickening or gelling properties. A 3-level factorial design was used to study the combined effect of different nitrate concentrations and photon flux density (PFD) values to evaluate the biomass and EPS production of A. platensis. The best result in terms of biomass production was obtained under condition 6 (2 g.L-1 NaNO3 and 600 μE.m-2.s-1) yielding a concentration of 1.292 g.L-1. However, condition 1 (0.25 g.L-1 NaNO3 and 200 μE.m-2.s-1) produced the greatest EPS yield (111 mg.g-1), followed by condition 9 (2 g.L-1 NaNO3 and 1000 μE.m-2.s-1). FTIR analyses of EPS samples indicated the presence of carboxylate and sulfate functional groups, and rheological studies of the EPS at 5 and 10 g.L-1 revealed a dilute solution behavior.

Oil-in-water emulsions of vitamin D incorporated in pecan oil were developed, using xanthan gum (XG) as a stabilizer. Fourteen formulations, composed of 2% surfactants, 5% pecan oil/vitamin D3 and 93% water were prepared in the presence of the hydrophilic Tween 20® and lipophilic Span 80® surfactants at different compositions. The hydrophilic/lipophilic balance (HLB = 10.70) of the oil phase, which led to the slowest rate of creaming and the lowest amount of creaming after 90 days, was chosen as the best composition of the nonionic surfactants. Using XG as stabilizing agent at 0.25, 0.5 and 1.0% concentrations, preliminary tests were carried out to evaluate the rheological properties and droplet size distribution of the emulsions. Their stability were also investigated after being submitted to environment stresses (centrifugation cycles, and storage at varying temperatures for 30 days). The emulsions prepared with XG at 0.5% concentration maintained their stability after five centrifugation cycles at 3000 rpm for 30 min, and after storage at 4, 25 and 40 °C, as revealed by rheological and droplet size measurements.

This study was conducted with the objective of investigating the physical and antimicrobial properties of structured zinc oxide compounds in chitosan submitted to different times of ultrasonic treatment. Zinc oxide particles were dispersed in water and coated with medium molar mass chitosan and two other sonicated samples, following a simple methodology. Before drying, the chitosan/zinc oxide water suspensions were characterized by rheological tests. Their rheological behavior depended on the period of time during which the chitosan sample was submitted to ultrasound. After drying, the microparticles were characterized by infrared spectroscopy, atomic absorption spectrophotometry and scanning electron microscopy (SEM). The microparticles were investigated as for their particle size distribution (PSD). SEM and PSD results revealed that the chitosan/zinc oxide microparticles had a multimodal dispersion. The antibacterial activity of the neat zinc oxide nanoparticles and of the microparticles was evaluated against Escherichia coli and Staphylococcus aureus. The results showed that the ZnO nanoparticles had a lower minimum bactericidal concentration (500 μm/mL against E. coli and 650 μm/mL against S. aureus) than the chitosan-coated/ZnO microparticles. The microparticles with the lowest average particle size and the highest homogeneity exhibited the highest antibacterial activity against both bacteria. This result was attributed to the additional antibacterial activity of soluble zinc ions and of the chitosan sample.

This study aimed to produce and characterize edible films and coatings from fruit and vegetable residue (FVR) flour and potato peel (P) flour. Two coating approaches (immersion and film) were studied on the quality of acerolas.Film-forming solutions (FFS) presented a viscoelastic behavior and a gelation process occurring at 70 °C. Maximum density (1.018 g cm(-3) ), viscosity (44.404 cP) and starch content were obtained for FFS based on 8% FVR flour with 4% P flour. This same film presented enhanced mechanical properties such as tensile strength and elongation at break (0.092 MPa and 36% respectively). Solubility of the films averaged 87%, demonstrating high hydrophilicity. Improved performance was obtained for film-packaged acerolas, which exhibited an increase in shelf life of 50% compared with control fruits. A lower loss of weight was observed for these samples by about 30-57% compared with control fruits, but minor modifications of pH, titratable acidity and soluble solid content occurred during storage.This study demonstrated the potential of FVR flour for edible coating and film formulation. Practical application on acerolas constituted a motivating route to evaluate and optimize this process; however, microbiological and sensory analyses are necessary to assess the material acceptability and safety.

Galactomannans obtained from Cassia javanica, Caesalpinia pulcherrima and Prosopis juliflora seeds, as well as commercial samples of locust bean gum (LBG) and guar gum (GG), were submitted to extraction and purification procedures. Viscometric measurements of their dilute aqueous solutions were performed in a Low Shear 40 rheometer in the shear rate range of 10−3 to 102 s−1. To obtain the intrinsic viscosity of these galactomannans, additional purification procedures, filtration through 0.45 μm membranes or centrifugation at 12 000 rpm for 1 h, were carried out. Intrinsic viscosities and Huggins' coefficient values were substantially different, depending on the purification method used. The results were attributed to differences in fine structure.

A galactomanana de sementes de Caesalpinia pulcherrima foi extraída em água e purificada, com rendimento de 25 %. A razão D-manose/D-galactose, M/G = 3,1, viscosidade intrínseca, [h] = 11,2 dL/g (em água a 298 K), e a massa molar viscosimétrica média, ou = 1,7 x 10(6), foram determinadas. A variação da viscosidade específica sob taxa de cisalhamento zero, hsp0, em função do parâmetro de sobreposição, C[h], mostrou dependências de hsp0 a (C[h])1,1 e de hsp0 a (C[h])4,2, nos regimes diluído e concentrado, respectivamente. A correlação entre as propriedades reológicas sob cisalhamento contínuo e dinâmico obedeceram satisfatoriamente ao princípio de Cox-Merz. The galactomannan from the seeds of Caesalpinia pulcherrima was extracted in water and obtained in 25 % yield, after purification. The D-mannose to D-galactose ratio, M/G = 3.1, the intrinsic viscosity, [h] = 11.2 dL/g (in water and 298K), and the viscosity-average molar mass, or = 1.7 x 10(6), were determined. The dependence of the specific viscosity at zero shear rate, hsp0, on the coil overlap parameter, C[h], showed slopes of 1.1 and 4.2 for the dilute and concentrated regimes, respectively. The Cox-Merz rule was followed satisfactorily by solutions submitted to steady and dynamic flows.

The galactomannan from Prosopis juliflora (PJ galactomannan) was extracted from milled seeds in water at 50 ºC. Its structural and solution properties were characterised in comparison with a commercial sample of guar gum (GG galactomannan). After partial degradation, the resulting samples were submitted to 13C-NMR spectroscopy. The mannose to galactose (M/G) ratios of PJ (M/G = 1.64) and GG (M/G = 1.85) galactomannans were estimated from the relative peak areas of the corresponding C-1 lines. Expansion of the C-4 lines revealed differences in the fine structure of the two galactomannans. The intrinsic viscosity determined for the GG sample, [eta] = 10.3 dL g-1, was slightly higher than that determined for PJ galactomannan, [eta] = 9.4 dL g-1. Dynamic experiments carried out at the same concentrations showed similar viscoelastic behaviours for the two gums. No enhancement in the storage modulus (G¢) was observed for kappa-carrageenan/PJ mixed solution in 0.1 mol L-1 KCl at 1.0 g L-1 total polymer concentration, in relation to kappa-carrageenan alone. Self-supporting gels obtained by mixing kappa-carrageenan and PJ or GG galactomannans in 0.25 mol L-1 KCl at 10 g L-1 total polymer concentration displayed similar mechanical properties. A galactomanana de Prosopis juliflora (PJ) foi obtida por extração em água, a 50 °C, a partir de sementes moídas. As suas características estruturais e as propriedades em solução foram comparadas com as de uma amostra comercial de goma guar (GG). Após degradação parcial, as amostras resultantes foram submetidas à espectroscopia de 13C RMN. As razões manose/galactose de PJ (M/G = 1,64) e de GG (M/G = 1,85) foram determinadas a partir das áreas relativas aos picos atribuídos a C-1. A expansão das linhas do C-4 revelaram diferenças na estrutura fina das duas galactomananas. A viscosidade intrínseca determinada para a amostra de GG, [eta] = 10,3 dL g-1, foi ligeiramente maior do que a determinada para a PJ, [eta] = 9,4 dL g-1. Experimentos dinâmicos realizados nas mesmas concentrações mostraram comportamentos viscoelásticos similares para as duas gomas. Nenhum aumento no módulo de armazenamento (G¢) foi observado para misturas kapa-carragenana/PJ em 0,1 mol L-1 KCl em uma concentração total de 1,0 g L-1, em relação à kapa-carragenana sozinha. Géis fortes, obtidos pela mistura de kapa-carragenana e PJ ou GG em 0,25 mol L-1 KCl em uma concentração total de 10 g L-1 apresentaram propriedades mecânicas similares.