O trabalho aqui apresentado mostra que a adição da GA, um polissacarídeo neutro não gelificante, a soluções de IPSL, modifica o mecanismo de gelificação induzido termicamente das PSL, bem como as propriedades viscoelásticas dos géis, reflectindo-se consequentemente na microestrutura dos géis finais. A extensão destas alterações depende da massa molecular da GA e da razão IPSL/GA.
A presença da GA apresenta um efeito positivo na formação de géis de IPSL, a pH neutro, podendo ser, provavelmente explicado pela ocorrência de interacções segregativas entre os dois biopolímeros.
Os resultados obtidos por microscopia confocal de varrimento laser sugerem a existência de separação de fases entre a GA e o IPSL, excepto para os sistemas contendo a fracção de GA de menor massa molecular (GA 960). Regra geral, a matriz proteica forma uma fase contínua que acomoda as cadeias de polissacarídeo, as quais preenchem os espaços vazios da rede proteica. A pH 7, os géis de IPSL apresentam uma microestrutura particulada, resultante da associação de moléculas de pequeno diâmetro, e possuem espaços capilares vazios de dimensão reduzida (Tavares e Lopes da Silva, 2003). Consequentemente, o aprisionamento de cadeias de GA, com propriedades distintas, nomeadamente, quanto ao seu tamanho no interior da matriz proteica, desencadeia diferentes efeitos a nível das propriedades viscoelásticas dos géis finais.
A consequência da segregação dos biopolímeros e da concentração local de cada componente, para o comportamento reológico dos géis, consiste essencialmente, na obtenção de géis mais rígidos, e na diminuição da concentração crítica de gelificação. Contudo, a extensão destes efeitos é dependente da massa molecular e da concentração da GA aplicada nos sistemas mistos. Para a GA com massa molecular e em concentração mais elevada verifica-se que o gel final obtido possui carácter viscoso mais acentuado e extensa separação de fases, com formação de uma fase contínua rica em polissacarídeo. Provavelmente, para elevadas concentrações de GA de elevada massa molecular, o efeito será prejudicial à formação de um gel com elevada elasticidade e grau de perfeição da rede tridimensional, podendo mesmo prever-se que a gelificação seria inibida caso se conseguisse atingir valores mais elevados de polissacarídeo.
Do ponto de vista prático, estes resultados mostram que uma gama variada de propriedades (reológicas e microestruturais) pode ser obtida alterando a massa molecular do polissacarídeo inserido num sistema misto IPSL/GA, possibilitando obter diferentes texturas e microestruturas com potencial aplicação em diferentes áreas.
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