Effect of sucrose on the phase and flow behaviour of polysaccharide/protein aqueous two-phase systems

The phase and flow behaviour of two model polysaccharide/protein aqueous two-phase systems (atps) locust bean gum (LBG)/sodium-caseinate (NaCas) and guar gum (GG)/NaCas - have been investigated in the presence of varying amounts of sucrose. The phase behaviour of these atps was found to be affected by the concentration of sugar in the system. An increase in the miscibility of these mixtures was initially induced by addition of sugar in concentrations up to 15 wt%, but further increase had the opposite effect, thus increasing the incompatibility between the polysaccharide and protein macromolecules. The rheological behaviour of these atps was found to relate to their microstructure under quiescent conditions. Depending on the phase sense in the quiescent atps the occurrence of a shear-induced phase inversion event was observed; phase inversion occurred only in those atps where the more viscous polysaccharide-rich phase was included. Addition of sugar in concentrations up to 20 wt% did not seem to affect the occurrence of phase inversion, but further increase in the sugar concentration was found to suppress this phenomenon. (c) 2009 Elsevier Ltd. All rights reserved.