Página 1 dos resultados de 1152 itens digitais encontrados em 0.004 segundos

Insulin encapsulation in reinforced alginate microspheres prepared by internal gelation

Silva, Catarina M.; Ribeiro, António J.; Ferreira, Domingos; Veiga, Francisco
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
ENG
Relevância na Pesquisa
36.98%
Insulin-loaded alginate microspheres prepared by emulsification/internal gelation were reinforced by blending with polyanionic additive polymers and/or chitosan-coating in order to increase the protection of insulin at simulated gastric pH and obtain a sustained release at simulated intestinal pH. Polyanionic additive polymers blended with alginate were cellulose acetate phtalate (CAP), Eudragit® L100 (EL100), sodium carboxymethylcellulose (CMC), polyphosphate (PP), dextran sulfate (DS) and cellulose sulfate (CS). Chitosan-coating was applied by using a one-stage procedure. The influence of additive polymers and chitosan-coating on the size distribution of microspheres, encapsulation efficiency and release profile of insulin in simulated gastrointestinal pH conditions was studied. The mean diameter of blended microspheres ranged from 65 to 106 [mu]m and encapsulation efficiency of insulin varied from 14 to 100%, reaching a maximum value when CS and DS were incorporated in the alginate matrix. Insulin release, at pH 1.2, was almost prevented by the incorporation of PP, DS and CS. When uncoated microspheres were transferred to pH 6.8, a fast dissolution occurred, independently of the additive polymer blended with alginate, and insulin was completely released. Increasing the additive polymer concentration in the alginate matrix and/or chitosan-coating the blended alginate microspheres did not promote a sustained release of insulin from microspheres at pH 6.8.; http://www.sciencedirect.com/science/article/B6T25-4K96S9W-1/1/bb451711b57f87e0d07aa047f0788cd5

Alginate microspheres prepared by internal gelation: Development and effect on insulin stability

Silva, Catarina M.; Ribeiro, António J.; Figueiredo, Isabel Vitória; Gonçalves, Alexandra Rocha; Veiga, Francisco
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
ENG
Relevância na Pesquisa
37.14%
Recombinant human insulin was encapsulated within alginate microspheres by the emulsification/internal gelation technique with the objective of preserving protein stability during encapsulation procedure. The influence of process and formulation parameters was evaluated on the morphology and encapsulation efficiency of insulin. The in vitro release of insulin from microspheres was studied under simulated gastrointestinal conditions and the in vivo activity of protein after processing was assessed by subcutaneous administration of extracted insulin from microspheres to streptozotocin-induced diabetic rats. Microspheres mean diameter, ranging from 21 to 287 [mu]m, decreased with the internal phase ratio, emulsifier concentration, mixer rotational speed and increased with alginate concentration. Insulin encapsulation efficiency, near 75%, was not affected by emulsifier concentration, mixer rotational speed and zinc/insulin hexamer molar ratio but decreased either by increasing internal phase ratio and calcium/alginate mass ratio or by decreasing acid/calcium molar ratio and alginate concentration. A high insulin release, above 75%, was obtained at pH 1.2 and under simulated intestinal pH a complete dissolution of microspheres occurred. Extracted insulin from microspheres decreased hyperglycemia of diabetic rats proving to be bioactive and showing that encapsulation in alginate microspheres using the emulsification/internal gelation is an appropriate method for protein encapsulation.; http://www.sciencedirect.com/science/article/B6T7W-4J4B994-3/1/737714c13ec0b481ae55c4c1c319f3e1

Chitosan-reinforced alginate microspheres obtained through the emulsification/internal gelation technique

Ribeiro, António J.; Silva, Catarina; Ferreira, Domingos; Veiga, Francisco
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
ENG
Relevância na Pesquisa
36.98%
Alginate microspheres prepared by emulsification/internal gelation were chosen as carriers for a model protein, hemoglobin (Hb). Reinforced chitosan-coated microspheres were obtained by an uninterrupted method, in order to simplify the coating process, minimize protein losses during production and to avoid Hb escape under acidic conditions. Microspheres recovery was evaluated as well as its morphology by determination of Hb encapsulation efficiency and microscopic observation, respectively. The formation of chitosan membrane made of it interaction with alginate was assessed by DSC (differential scanning calorimetry) and FT-IR (Fourier-transform infrared spectrometry) studies. Spherical uncoated microspheres with a mean diameter of 20 [mu]m and encapsulation efficiency above 89% were obtained. Coated microspheres provided similar encapsulation efficiency but a higher mean diameter was obtained due to microspheres clumping during the coating step. Protein loss occurred mainly during emulsification rather than recovery. FT-IR and DSC together indicated electrostatic interactions between alginate carboxylate and chitosan ammonium groups as the main forces for complex formation.; http://www.sciencedirect.com/science/article/B6T25-4FM5CXS-1/1/2db2be842f728a0541def21ac050a44e

Microencapsulation of hemoglobin in chitosan-coated alginate microspheres prepared by emulsification/internal gelation

Silva, Catarina; Ribeiro, António; Figueiredo, Margarida; Ferreira, Domingos; Veiga, Francisco
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.14%
Chitosan-coated alginate microspheres prepared by emulsification/internal gelation were chosen as carriers for a model protein, hemoglobin (Hb), owing to nontoxicity of the polymers and mild conditions of the method. The influence of process variables related to the emulsification step and microsphere recovering and formulation variables, such as alginate gelation and chitosan coating, on the size distribution and encapsulation efficiency was studied. The effect of microsphere coating as well its drying procedure on the Hb release profile was also evaluated. Chitosan coating was applied by either a continuous microencapsulation procedure or a 2-stage coating process. Microspheres with a mean diameter of less than 30 µm and an encapsulation efficiency above 90% were obtained. Calcium alginate cross-linking was optimized by using an acid/CaCO3 molar ratio of 2.5, and microsphere-recovery with acetate buffer led to higher encapsulation efficiency. Hb release in gastric fluid was minimal for air-dried microspheres. Coating effect revealed a total release of 27% for 2-stage coated wet microspheres, while other formulations showed an Hb release above 50%. Lyophilized microspheres behaved similar to wet microspheres, although a higher total protein release was obtained with 2-stage coating. At pH 6.8...

Influence of gelation time on the morphological and physico-chemical properties of the sol-gel entrapped lipase

PINHEIRO, Rubiane C.; SOARES, Cleide M. F.; SANTOS, Onelia A. A. dos; CASTRO, Heizir F. de; MORAES, Flavio F. de; ZANIN, Gisella M.
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.32%
Different gelation times (4, 18, 24 and 48 h) were used for the preparation of silica sol-gel supports and encapsulated Candida rugosa lipase using tetraethoxysilane (TEOS) as precursor. The hydrophobic matrices and immobilized lipases produced were characterized with regard to pore volume and size by nitrogen adsorption (BJH method), weight loss upon heating (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), chemical composition (FTIR) and percentage of hydrolysis (POH%) of olive oil. These structural parameters were found to change with the gelation time, but no direct relation was found between the percentage of oil hydrolysis (POH%) and the gelation time. The best combination of high thermal stability and high POH% (99.5%) occurred for encapsulated lipase produced with 24 h gelation time. (C) 2007 Elsevier B.V. All rights reserved.

Efeitos de variáveis do processo de gelificação interna nas propriedades físicas e químicas de microesferas de alumina; Variable effects of the internal gelation process in the physical and chemical properties of alumina microspheres

Christe, Charles de Miranda
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 18/12/2012 PT
Relevância na Pesquisa
37.14%
Microesferas cerâmicas vêm sendo utilizadas em diferentes aplicações, relacionadas à área nuclear, farmacêutica, química, médica, ambiental, biotecnológica, etc. É possível a obtenção, pelo método da gelificação interna, de microesferas de diferentes materiais cerâmicos, densas ou porosas (com porosidade controlada) e com diferentes tamanhos. No entanto o grande obstáculo é a formação de trincas na secagem e/ou calcinação, que podem inviabilizar a aplicação das mesmas. Este trabalho tem como objetivo a produção de microesferas a base de alumina (Al2O3) pelo processo de gelificação interna, variando-se parâmetros de processamento de forma a se controlar as características físicas e químicas das mesmas, como tamanho, porosidade, superfície específica, etc., além de características específicas que viabilizem a aplicação das mesmas no preenchimento de colunas de eluição de geradores de 99Mo-99mTc. Foi desenvolvida uma metodologia simples e eficiente de tratamento de lavagem das microesferas, que possibilita a extração de uma porção significativa da fase orgânica presente antes da secagem e calcinação; desta forma elimina-se praticamente todas as trincas que surgiriam durante a secagem, e principalmente na etapa de calcinação. Além disso...

Electrical percolation during gelation of lithium doped siloxane-poly(oxyethylene) hybrids

Sacco, A. P.; Dahmouche, K.; Santilli, C. V.; Pulcinelli, S. H.
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica Formato: 303-309
ENG
Relevância na Pesquisa
37.24%
Gelation mechanisms of lithium-doped Siloxane-Poly(oxyethylene) (PEO) hybrids containing polymer of two different molecular weight (500 and 1900 g/mol) were investigated through the evolution of the electrical properties during the solgel transition. The results of electrical measurements, performed by in-situ complex impedance spectroscopy, were correlated with the coordination and the dynamical properties of the lithium ions during the process as shown by Li-7 NMR measurements. For both hybrids sols, a decrease of the conductivity is observed at the initial gelation stage, due to the existence of an inverted percolation process consisting of the progressive separation of solvent molecules containing conducting species in isolated islands during the solid network formation. An increase of conductivity occurs at more advanced stages of gelation and aging, attributed to the increasing connectivity between PEO chains promoted by the formation of crosslinks of siloxane particles at their extremities, favoring hopping motions of lithium ions along the chains.

Effect of electrolyte on the gelation and aggregation of SnO2 colloidal suspensions

Hiratsuka, Renato Satoshi; Santilli, Celso Valentim; Silva, Dileize Valeriano; Pulcinelli, Sandra Helena
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 67-73
ENG
Relevância na Pesquisa
37.24%
Electrolytes may modify the physical-chemical characteristics of colloidal particle interfaces in suspension, which can favour gel or aggregate formation. The influence of NH4Cl loading on the aggregation and gelation of SnO2 colloidal suspensions was investigated using measurements of rheology, turbidity and infrared spectra. A rapid aggregate growth for samples with Cl- > 20 mM was observed. With increasing age, gelation was observed due to formation of interaggregate bonds. For concentration of Cl- between 20 and 9 mM, the aggregation process was slower allowing the formation of gel with a network which was not destroyed as the gel was submitted to a small rate of shear. As aging continues, the condensation reaction between OH groups gave rise to the formation of Sn-O bonds, irrespective of the electrolyte loading. © 1992 Elsevier Science Publishers B.V. All rights reserved.

Effect of lithium doping on the evolution of rheological and structural properties during gelation of siloxane-poly(oxypropylene) nanocomposites

Sarmento, V. H. V.; Dahmouche, K.; Pulcinelli, S. H.; Santilli, C. V.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 3962-3972
ENG
Relevância na Pesquisa
37.42%
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); The influence of lithium doping on the evolution of viscoelastic properties and structure during the gelation of siloxane-poly(oxypropylene) (PPO) nanocomposites has been studied. For several [O]/[Li] ratios (O being the oxygen of the ether-type), dynamic Rheological measurements allowed us to follow the evolution of storage and loss moduli, complex viscosity and phase angle during gelation of Li+-doped hybrid sols. All samples exhibit a Newtonian viscous character in the initial step of the process and are progressively transformed into viscoelastic gels. The evolution of the rheological properties of these systems allowed us to determine the aggregation mechanisms of silicon species present in hybrid sols, which lead to sol-gel transformation: mass fractal growth and nearly linear growth at the beginning of gelation, and percolation at the final stage of the process. The influence of doping on the aggregation mechanisms depends on the polymer molecular weight: while for hybrids containing long polymer chains (Mw = 4000 g mol-1) gelation occurs in the initial stages through diffusion-limited monomer-cluster aggregation (DLMCA) for all doping levels...

Gelificação a frio de proteinas do soro do leite : efeito da taxa de acidificação, pH final e adição de polissacarideos.; Cold set gelation of whey proteins : acidification rate, final pH and polysaccharide addition effects.

Angelo Luiz Fazani Cavallieri
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 10/04/2007 PT
Relevância na Pesquisa
37.24%
A gelificação a frio de soluções de isolado protéico de soro (WPI) foi realizada pela adição de diferentes quantidades de glucona-?-lactona (GDL) a soluções de WPI desnaturadas termicamente (80ºC/30 minutos). Foram analisados sistemas protéicos puros (WPI na concentração de 7% p/p) e mistos, após a adição de xantana ou guar (concentração WPI 5% fixa e de polissacarídeos, 0,1, 0,3 e 0,5% p/p). Estes sistemas exibiram diferentes taxas de acidificação e valores de pH final em torno do ponto isoelétrico das principais frações protéicas do soro (5,2 a 3,9). Nos sistemas protéicos puros foi possível distinguir dois estágios de desenvolvimento estrutural: 1-início da formação da rede até o ponto de gel, em que as propriedades reológicas não foram influenciadas pela taxa de acidificação, e 2- subseqüente desenvolvimento estrutural com a redução do pH devido a fortalecimento de ligações e rearranjos estruturais. O processo lento de acidificação levou a géis mais estruturados no pH final de 5,2 enquanto que a acidificação rápida produziu géis mais frágeis (pH 4,2), que mostraram rearranjo estrutural após a obtenção do pH final. No pH de equilíbrio em torno do pI, a capacidade de retenção de água foi menor...

Produção de microparticulas por gelificação ionica para alimentação de larvas de peixe : estudos em sistema-modelo com incluão de microparticulas lipidicas ou emulsão lipidica e testes in vivo.; Production of microparticles by ionic gelation for fish larvae feeding : studies in model-system with inclusion of lipids microparticles or emulsion and assays in vivo.

Renata Mukai Correa
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 08/07/2008 PT
Relevância na Pesquisa
37.14%
Este estudo teve como objetivo produzir micropartículas por gelificação iônica contendo, como recheios, constituintes nutricionalmente importantes para a alimentação de larvas de peixes. Na primeira parte deste estudo, foram desenvolvidos sistemas modelos compostos por micropartículas obtidas por gelificação iônica utilizando os polissacarídeos pectina e a mistura ternária: pectina/gelana/alginato e íons cálcio para formação das matrizes. Como conteúdo, foram incorporados compostos hidrofílicos (glicose e isolado protéico de soro de leite) na forma de micropartícula ou emulsão lipídica, utilizando uma mistura lipídica (gordura de peixe/ácido esteárico) contendo surfactantes (monoestearato de sorbitana+triesterato de sorbitana). Esses sistemas foram caracterizados em relação à eficiência de encapsulação, eficiência de inclusão, hidratação, tamanho médio e sua distribuição, morfologia e composição centesimal. Os sistemas preparados na forma de emulsão lipídica apresentaram uma distribuição mais homogênea do conteúdo das micropartículas e liberação de proteínas significativamente menor (p<0,05) do que os sistemas contendo micropartículas lipídicas, sendo os compostos por pectina/gelana/alginato...

Partículas de alginato e pectina produzidas por gelificação iônica e recobertas com proteínas; Alginate and pectin particles produced by ionic gelation and coated with proteins

Fernando Tello Célis
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 28/03/2014 PT
Relevância na Pesquisa
37.24%
A encapsulação permite a formação de estruturas que apresentam propriedades como a proteção e liberação controlada do material encapsulado. As características do material encapsulado determinam a escolha do material de parede da matriz encapsulante e da técnica de encapsulação. Proteínas e polissacarídeos têm sido investigados para a formação destas matrizes. Diferentes técnicas produzem partículas com diferentes propriedades. A associação de técnicas de encapsulação permite a obtenção de matrizes com melhores propriedades tecnológicas. A gelificação iônica é uma técnica de encapsulação branda, simples e rápida onde polissacarídeos aniônicos interagem com íons divalentes como o Ca2+ para a encapsulação de diversos tipos de compostos incluindo lipídicos. Neste estudo, pectina e alginato foram utilizados para produção de partículas por gelificação iônica. Na primeira parte do estudo, partículas produzidas por gelificação iônica com alginato ou pectina foram revestidas com proteínas da clara de ovo, de soro do leite e da mistura (1:1) das referidas proteínas utilizando-se diferentes concentrações de proteínas em solução a pH 4,0. Partículas de alginato aumentaram de tamanho após revestimento proteico enquanto partículas de pectina diminuíram de tamanho. Aumento da concentração desta na solução produziu aumento na quantidade de proteína adsorvida e de matéria seca nas partículas. Para o maior nível de adsorção proteica...

Developing scaffolds for tissue engineering using the Ca2+-induced cold gelation by an experimental design approach

Ribeiro, Artur J.; Gomes, Andreia; Paulo, Artur Cavaco
Fonte: Wiley Publicador: Wiley
Tipo: Artigo de Revista Científica
Publicado em //2012 ENG
Relevância na Pesquisa
37.14%
The Ca2+-induced cold gelation technique was found suitable to prepare highly porous biodegradable scaffolds based on bovine serum albumin (BSA) and alpha-casein from bovine milk for tissue engineering. A 23 full factorial design was used to study the influence and impact of each factor on the several responses of the scaffolds. In vitro degradation (ID), swelling ratio (SR), porosity (PO), and pore size (PS) as well cytotoxicity (CT) were evaluated and shown to be dependent on the pH of sample preparation and on the amount of BSA and casein present, making these scaffolds tunable structures. Under optimized working conditions (4.19% of BSA, 0.69% of Casein, pH 7.07), the ID attained was 37.97%, the SR observed was 11.87, the PO was 82.11%, the PS measured was 180.63 μm at surface, and 175.91 μm at fracture, whereas maximum cell viability was 84% in comparison to controls. Moreover, the scaffold supported cell adhesion and proliferation. These results, consistent with the prediction by the experimental design approach, support the use of this methodology to develop tunable scaffolds for tissue engineering using the Ca2+-induced cold gelation.

Association of riboflavin in whey protein hydrogels produced through application of moderate electric field and cold induced gelation

Pereira, Ricardo; Altinok, Emir; Rodrigues, Rui M.; Ramos, Óscar L.; Malcata, F. X.; Ferrari, Giovanna; Teixeira, J. A.; Vicente, A. A.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em 15/10/2014 ENG
Relevância na Pesquisa
37.37%
Protein hydrogels are one of the most convenient and widely used matrix in food applications. Recently, cold gelation ability of whey protein isolate (WPI) is taking interest in protection and delivery of value-added bioactive compounds through micro and nano-association techniques. This study aims to combine an electro-heating treatment at moderate electric fields (MEF) together with cold gelation ability of whey proteins in order to reduce size of protein aggregates at nano-scale and improve association efficiency of riboflavin. Divalent iron cation assisted cold gelation of electro-heated WPI and effects of MEF on the produced hydrogels were reported and encouraged during this experimental research. Particle size was characterized, through dynamic light scattering. While spectrofluorimetric analyses were performed in order to examine the effects of MEF and cold induced gelation on the association of riboflavin within WPI hydrogel network structure. Under MEF application smaller sized particles were produced and riboflavin association efficiencies ranged from 40 to 60%. Results also show that MEF treatment allowed producing WPI nano-hydrogels with associated riboflavin less susceptible to light oxidation. This novel approach that combines electro-heating treatment together with cold gelation can be used to design and develop entirely biodegradable whey protein-based gels as potential devices for controlled release of riboflavin. MEF can be used to improve or create novel applications not only in food and bioprocessing industries...

Kinetics and thermal behaviour of the structure formation process in HMP/sucrose gelation

Silva, J. A. Lopes da; Gonçalves, M. P.; Rao, M. A.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //1995 ENG
Relevância na Pesquisa
37.37%
The concentration and temperature dependence of the gelation kinetics of high-methoxyl pectin (HMP; 60% sucrose, pH 3) was investigated using measurements of small-amplitude oscillatory shear. The rate of gelation close to the gel point can be described as a second-order rate process using the kinetic model of Ross-Murphy (Carbohydr. Polym. 1991, 14, 281) and a critical exponent close to that predicted by the percolation approach. The modulus after a long ageing time showed a power concentration dependence with an exponent around 3.1, higher than the classical square of concentration dependence, which was probably either due to the non-equilibrium state of the HMP gels even after long ageing times, or due to the proximity of the concentration range studied to the critical gelling concentration. The gelation rate of HMP/sucrose systems is strongly dependent on the temperature. An Arrhenius relationship was applied to describe this dependence. Two different processes are proposed to explain the discontinuity observed, each one having rates with different temperature dependence. The applicable kinetics at longer times are quite different, with a lower dependence on polymer concentration and ageing temperature. A non-isothermal kinetic model was used to describe the gelation process of the HMP/sucrose system during cooling.

Effect of composition of commercial whey protein preparations upon gelation at various pH values

Ramos, O. L.; Pereira, J. O.; Silva, S. I.; Amorim, M. M.; Fernandes, J. C.; Lopes da Silva, J. A.; Pintado, M. E.; Malcata, F. X.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.24%
The major goal of this research effort was to comprehensively characterize various whey protein products available in the market — including one whey protein isolate (WPI) and three whey protein concentrates (two forms of WPC 80, and WPC 50), with regard to the effects of specific components (e.g. lecithin and minerals) and concentration of β-lactoglobulin (β-Lg) and α-lactalbumin upon thermal and gelation properties at various pH values (using micro differential scanning calorimetry, μDSC, and oscillatory rheometry). At pH values far from the isoelectric point of whey proteins, denaturation and aggregation appeared as one single endothermic peak in the corresponding μDSC heating thermograms, for WPI and both WPC 80; however, they appeared as separate transitions at pH 5. Acidic conditions increased the temperature of occurrence of the dominant endothermic transition associated to β-Lg, thus increasing the thermal stability of WPI, WPC 80A and WPC 80B. Gelation took place at the lowest temperature when pH was set at 5. WPI, WPC 80A and WPC 80B exhibited the highest G′ values at pH 5 — whereas WPI led to stronger gels than WPC, irrespective of pH. In the case of WPC 50, gelation did not occur at all.

Effect of gelation temperature on the properties of skim milk gels made from plant coagulants and chymosin

Esteves, Cristina L. C.; Lucey, John A.; Hyslop, Douglas B.; Pires, Euclides M. V.
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
ENG
Relevância na Pesquisa
37.45%
Reconstituted skim milk was gelled at 25-40°C with the plant-origin coagulants from Cynara cardunculus L. or Cynara humilis L. or with fermentation-produced chymosin. Gel formation and ageing were monitored by low amplitude oscillatory rheology and confocal scanning laser microscopy. Arrhenius plots for the rate of milk gelation were also determined. Plant coagulants had shorter gelation time (tg) at 25°C, 35°C and 40°C, and higher initial rate of increase in G' values at all temperatures tested. The firmest gels at long ageing times were produced by chymosin at 30°C and 32°C. At a gelation temperature of 25°C, the differences in rheological and microstructural characteristics between plant coagulants and chymosin were considerable; plant coagulants had shorter tg and higher G' values. For the lowest gelation temperatures, plant coagulants had smaller activation energy values for gelation. Most of the gelation results were similar between plant coagulants, but some differences were found in the values of tg, the rate of increase in G' and loss tangent parameter. The characteristics of gels produced with plant coagulants were influenced less by the changes in temperature compared with chymosin-produced gels, which may be an important consideration in using plant-origin coagulants in the production of cheeses with a wider range of gelation temperatures.; http://www.sciencedirect.com/science/article/B6T7C-493HNG1-1/1/35f20b14e49b2922b16639bac3576d19

Autoensamblaje del caseinomacropéptido (CMP) y su impacto en la gelificación y espumado; Casinmacropeptide (CMP) self-assembly and its impact on gelation and foam

Farías, María Edith
Fonte: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires Publicador: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires
Tipo: info:eu-repo/semantics/doctoralThesis; tesis doctoral; info:eu-repo/semantics/publishedVersion Formato: application/pdf
Publicado em //2012 SPA
Relevância na Pesquisa
37.14%
El objetivo de este trabajo fue estudiar mediante dispersión dinámica de luz (DLS) el autoensamblaje del caseinomacropéptido (CMP) en relación al pH, tipo de ácido y presencia de sales y su impacto en la gelificación y el espumado. A pH 7,0, las soluciones de CMP son estables con el tiempo y no gelifican aún bajo calentamiento. La forma predominante del CMP en estas condiciones es la monomérica. A pH < 4,5 ya sea a temperatura ambiente o por calentamiento, el CMP genera en el tiempo una estructura ordenada gelificada de características viscoelásticas, baja dureza y cohesividad. Dicha estructura es reversible a un cambio ulterior de pH pero no a la forma monomérica original. Se propuso un modelo de autoensamblaje y gelificación del CMP. El autoensamblaje del CMP y su gelificación están modulados por diferentes condiciones del medio: pH, temperatura, tipo de ácido y presencia de sales. El tipo de ácido y la presencia de sales impactan en la asociación del CMP por vía hidrofóbica, la cual constituye la primera etapa del autoensamblaje, conduciendo a dímeros (HCl), tetrámeros (ácido cítrico, ácido láctico, NaCl, CaCl2) o hexámeros (ácido acético). Estas formas asociadas del CMP son las que posteriormente interactúan a pH < 4...

Ultrasonic propagation and thermal changes during milk gelation processes

Elvira Segura, Luis; Resa López, Pablo Ismael; Montero de Espinosa Freijo, Francisco
Fonte: Sociedad Española de Acústica Publicador: Sociedad Española de Acústica
Tipo: Comunicación de congreso Formato: 193755 bytes; application/pdf
ENG
Relevância na Pesquisa
37.24%
6 pages, 6 figures.-- PACS nr.: 43.35.Bf, 43.35.Zc.-- Communication presented at: Forum Acusticum Sevilla 2002 (Sevilla, Spain, 16-20 Sep 2002), comprising: 3rd European Congress on Acoustics; XXXIII Spanish Congress on Acoustics (TecniAcústica 2002); European and Japanese Symposium on Acoustics; 3rd Iberian Congress on Acoustics.-- Special issue of the journal Revista de Acústica, Vol. XXXIII, year 2002.; An ultrasonic measurement technique for gelation monitoring of dairy products is presented in this work. An ultrasonic pulse is emitted and received after travelling through the milk during two different processes: rennet coagulation and yoghurt formation. Changes of the ultrasonic propagation parameters containing information about the milk gelation process are reported. The temperature changes during gelation were also measured and its influence over the ultrasonic propagation was evaluated. This non-invasive and real-time measurement technique appears as an interesting method for quality control in the dairy industry.; Peer reviewed

Porometry Studies of the Polysulfone Membranes on Addition of Poly(ethylene Glycol) in Gelation Bath During Preparation

Yogesh,S. Javiya; Gupta,S.; Singh,K.; Bhattacharya,A.
Fonte: Sociedad Química de México A.C. Publicador: Sociedad Química de México A.C.
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2008 EN
Relevância na Pesquisa
37.32%
Polysulfone membranes are prepared through phase separation technique, introduced by Loeb-Sourirajan. The viscous polymer solution (in dimethyl formamide) is first spread into the thin film, and then immersed in gelation medium (water). The influence of polymeric additive, (poly(ethylene glycol) (PEG)) in the formation of the pores during phase separation in gelation bath (i.e. from the polymer poor phase, which appears at the phase separation) is explored. The effects of different molecular weight (Mw) of PEG in the gelation bath regarding the differential filter flows of nitrogen as well as their concentration are reflected from the porometry studies. The pore distribution is shifted as the molecular weight of PEG used in the gelation bath. The bubble point and mean flow pore diameters vary with the concentration as well as their molecular weight of PEG.