Interaction of food polysaccharides with ovalbumin

Differential scanning calorimetry (DSC), rheometry, UV absorption and circular dichroism (CD) measurements were used to study the interaction of two food polysaccharides, namely carboxymethyl cellulose (CMC) and the chitin derivative glutamate glucan, with the main egg white protein (ovalbumin). The study was carried out on solutions of each polysaccharide and the protein. These solutions were prepared by mixing solutions containing only one biopolymer, or by solubilising the product obtained after heating the polysaccharide-protein colyophilizate at 60 degrees C. Solutions of the ovalbumin and of the polysaccharides, which separately underwent the same procedure, were taken as the reference. Both the CD and the DSC measurements indicated that the glutamate glucan was very effective in stabilising the native conformation of the globular protein ovalbumin and in reducing its temperature-induced precipitation in the presence of Ca2+ ions. The interaction with the polysaccharide occurred at both low and high temperatures. It is proposed that in solution a soluble complex between the glutamate glucan and native ovalbumin is formed. In the solid state at 60 degrees C the glutamate glucan and the ovalbumin probably react and a three-dimensional network is formed. Rheometry indicated that at 25 degrees C the CMC-ovalbumin systems phase separate as a result of the limited thermodynamic compatibility between these two types of polymers when an excess of ovalbumin is present. DSC showed that at higher temperatures an interaction is also suspected even between these species, when an excess of CMC is present. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.