Influence of temperature on the rheological behavior of jaboticaba pulp

The steady state and dynamic rheological behavior of jaboticaba pulp was studied at different temperatures (5, 25, 45, 65 and 85 T). Flow curves were obtained from 0 to 300 s(-1) and the data were fitted to different models. The Herschel-Bulkley model showed the best fit (R-2 > 0.98) to the experimental data. Increasing the temperature caused a decrease in the consistency index (k) and a slight increase in the flow index (n). Oscillatory rheological measurements were taken in the viscoelastic region to obtain mechanical spectra. The storage modulus (G') of samples stored at 5 degrees C was much higher than that recorded at other temperatures, indicating more intense particle interactions at this temperature, which contributed to strengthen the elastic network. At 45 degrees C, the jaboticaba pulp showed a distinct behavior, possibly indicating the beginning of gelation of the pulp's natural pectin.27489089

Effect of process variables on the osmotic dehydration of star-fruit slices

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)The objective of this work was to study the effect of blanching and the influence of temperature, solution concentration, and the initial fruit:solution ratio on the osmotic dehydration of star-fruit slices. For blanching, different concentrations of citric and ascorbic acids were studied. The samples immersed in 0.75% citric acid presented little variation in color in relation to the fresh star-fruit. Osmotic dehydration was carried out in an incubator with orbital shaking, controlled temperature, and constant shaking at 120 rpm. The influence of process variables was studied in trials defined by a complete 2(3) central composite design. In general, water loss and solids gain were positively influenced by temperature and by solution concentration. Nevertheless, lower temperatures reduced water loss throughout the osmotic dehydration process. An increase in the amount of dehydrating solution (initial fruit:solution ratio) slightly influenced the evaluated responses. The process carried out at 50 degrees C with a solution concentration of 50% resulted in a product with lower solids gain and greater water loss. Under these conditions, blanching minimized the effect of the osmotic treatment on star-fruit browning, and therefore the blanched fruits showed little variation in color in relation to the fresh fruit.322357365SAE (Servico de Apoio ao Estudante - UNICAMP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Effect of particle size on rheological properties of jaboticaba pulp

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Particle size (PS) influence on theological properties of jaboticaba pulp was evaluated, and the effect of a narrower particle size distribution (PSD) when compared to the whole pulp was observed. Particles separated from fresh pulp were wet sieved and reconstituted to serum at the same fraction as whole pulp. SEM analysis and oscillatory measurements of reconstituted samples showed that PS exerted a strong influence on rheological-structural behavior. Increasing PS from 64 up to 550 mu m promoted a rise of rheological properties of reconstituted pulps, being that the viscosity increased linearly from 0.06 to 0.40 Pa s. However, pulps with larger particles showed an abrupt decay of the steady state properties because of the sedimentation promoted by the instability of the internal network due to shear. The conditions of low deformation assays did not disturb the system stability, allowing the determination of the limit of linearity of all samples. The comparison of theological behavior between whole pulp and reconstituted samples with similar mean diameters showed that the broader PSD of the initial pulp led to a less viscous and structured suspension, indicating that not only PS, but mainly the PSD influences the rheological behavior of suspensions. (C) 2008 Elsevier Ltd. All rights reserved.914566570Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Influence of Dispersing Media and Particle Characteristics on Rheological Behavior of Noncolloidal Suspensions

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)The effect of viscosity (high and low) and molecular characteristics (polar and nonpolar) of continuous matrix on the flow behavior of noncolloidal suspensions were evaluated using particles with different size and shape. The increase in solids volume fraction exerted higher influence for larger cellulose fibers and less viscous matrices, due to larger particle-particle interaction. Evaluation of matrix polarity allowed the assessment of particle-solvent interactions, indicating that higher swelling of particles dispersed in polar matrices led to more complex and viscous suspensions. Besides particle characteristics, suspending matrix properties influenced the rheological behavior of noncolloidal suspensions, despite of the prevailing hydrodynamics effects.3341699437446Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)CNPq [140463/2005-4, 301869/2006-5

kappa-Carrageenan-sodium caseinate microgel production by atomization: Critical analysis of the experimental procedure

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)The influence of atomization process to produce kappa-carrageenan and kappa-carrageenan/sodium caseinate microgels was studied experimentally (aspect ratio and particle size distribution) and theoretically (dimensionless parameters). Moreover, rheological behavior of microgel suspensions was evaluated to examine their potential application in food products. Experimental results demonstrated that the size of microgels was influenced by feed flow rate, compressed air flow rate and composition of solutions, while their shape depended on the viscosity and surface tension of biopolymer solutions. Regarding the dimensionless numbers, higher values of Reynolds number of liquid layer (Rex(lambda l)) and Weber number (We(l)) led to smaller particles, while the decrease of Ohnesorge number (Oh) was related to lower sphericity of microgels. Rheological behavior of suspensions depended on not only the morphology and size of microgels, but also their composition. Incompatibility between kappa-carrageenan and sodium caseinate in mixed microgels led to suspensions with more complex rheological behavior at determined biopolymer concentrations. (C) 2010 Elsevier Ltd. All rights reserved.1041123133Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAPESP [2007/58017-5]CNPq [301869/2006-5

Rheology of mixed pectin solutions

The effects of sucrose (S) and pectin (P) concentrations and the ratio between two distinct pectins (R) on the rheological behavior of diluted pectin systems were evaluated simultaneously using the surface response methodology. The systems were composed of a mixture of two high methoxy pectins with different degree of methyl esterification values (HM1/HM2) and of a mixture of a high-methoxy with an amidated low-methoxy pectin (HM1/LMA). For the HM1/HM2 systems, the multivariate analysis showed that the sucrose and pectin concentrations exerted statistically significant (p < 0.05) linear effects on the consistency index k and viscosity, the influence of pectin being about five times higher than that of sucrose. The pectin concentration and the ratio between the different pectins were shown to be significant with respect to the rheological parameters of the HM1/LMA systems. Evaluating the influence of the ratio between the different pectins, a synergistic effect on the structure reinforcement was observed when mixing HM1 and LMA in similar proportions, indicating the importance of the presence of hydrophobic interactions between methyl ester groups in addition to the stronger hydrogen bonding in junction zone stabilization. In general, the conditions in which hydrogen bonds were favored in relation to hydrophobic interactions led to systems with higher pseudoplasticity.3110010

The effect of addition of calcium and processing temperature on the quality of guava in syrup

The effect of process temperature and calcium concentration in the cooking syrup of guava in syrup were studied. A central composite rotatable design (CCRD) was used to optimize the quality indices of the final product, such as texture and colour. All of the processed guava quality parameters were compared with those of the fresh fruit and of a commercial sample to evaluate the effects of processing on the final product quality. Increase in the process temperature promoted changes in the final product colour, the fruit becoming darker. On the contrary, higher calcium concentrations in the cooking syrup produced lighter samples, with colour parameters closer to those of the fresh fruit. In general, the addition of calcium promoted better texture and minimized the negative effects of temperature on the mechanical properties. Processed guavas had higher rupture stress and strain than fresh fruit, indicating an increase in hardness and elasticity.41441742

Development of gelled emulsions with improved oxidative and pH stability

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Olive oil emulsions were produced at high pressure homogenization (0-60 MPa), stabilized and gelled with gelatin, alginate or their mixture. Right after homogenization, these systems were evaluated according to their droplet size distribution and after gelation, uniaxial compression properties were assessed. Pure alginate emulsions showed larger mean droplet size and lower values of mechanical properties than emulsions with gelatin. Increasing homogenizing pressure led to monomodal droplets size distribution, although a weakening on gel structure was observed. For oxidative and pH stability assays, emulsions with smaller droplet sizes and polydispersity were chosen (40 MPa). Results of oxidative stability showed lower amount of primary and secondary oxidation products within the 30-day storage for the gelled emulsions as compared to a control sample (non-gelled). Considering the pH stability assays, results indicated that gelatin emulsions were not stable to any incubation condition at 37 degrees C. Alginate emulsions, on the other hand, showed to be relatively stable at the pH conditions evaluated, although a visible separated oil layer was observed at neutral pH. Generally, alginate-gelatin mixed emulsions showed enhanced oxidation and pH stability as compared to systems produced with only one biopolymer. Such improved stability of mixed gelled systems was associated to the emulsifying properties of gelatin with the high pH resistance of alginate as a delivery system. (c) 2012 Elsevier Ltd. All rights reserved.341184192Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAPESP [2009/51456-9, 2009/54137-1]CNPq [304611/2009-3

Effect of processing parameters on some physicochemical properties, sugar profile and rheological characterization of apricot sauce

In this study, effects of processing parameters including blanching temperature, time and sieve diameter on some physicochemical and rheological properties and sugar profile of apricot sauce were investigated. Eight apricot sauce samples were manufactured at different blanching temperatures (85 and 95 degrees C), blanching times (5 and 10 min) and sieve diameters (1 and 3 mm). The sauce samples were stored at + 4 degrees C for 60 days and analyses were performed at intervals of 15 days. It was observed that the processing variables and storage period affected the properties of samples significantly (p 0.97)