Mixed Polysaccharide Gels Formed between Xanthan Gum and Glucomannan

Abstract

The ability of polysaccharides to enhance viscosity and to form gels has led to their widespread use in food products. Often synergistic combinations of polysaccharides are employed in order to manipulate rheological characteristics and, in addition, to provide effective savings in production costs. Common examples of polysaccharide blends used include kappa-carrageenan-galactomannan, xanthan-galactomannan and alginate-pectin. The origin of the synergy in these polysaccharide mixtures has been the subject of extensive research studies over the last twenty years or so and still gives rise to considerable controversy ^1,2. Cairns et al ³ have identified four different types of gel structure that might arise in binary mixtures of polysaccharides and these are illustrated in figure 1. In structure a) only one of the polysaccharides contributes to the gel network and the second polymer is simply entrapped within the matrix. In structure b) both polysaccharides form independent penetrating networks. Structure c) arises if polymer demixing occurs prior to gelation giving a phase separated network and structure d) is termed a coupled network and arises when sections of the two polysaccharides associate.