Polysaccharide-protein interaction: a rheological study of the gel-sol transition of a gelatin-methylcellulose-water system.

Viscoelastic parameters for mixtures of gelatin and methylcellulose were measured as a function of temperature, in order to study the gel-sol transition of the system in which biopolymers forming thermo-setting and thermo-melting gels coexist. At higher temperatures than 45 degrees C, the gel network is mainly formed by methylcellulose while at lower temperatures around 5 degrees C, it is mainly formed by gelatin. At higher temperatures than 45 degrees C, gelatin inhibits the gelation of methylcellulose. A small amount of methylcellulose helps gelatin to form a network at lower temperatures. However, excessive amounts of methylcellulose inhibit the growth of network structure. Therefore, this mixture forms a phase separated gel at higher temperatures while it is not completely phase separated at lower temperatures, probably by some interaction between non-substituted hydroxyl groups in methylcellulose with carboxylic groups in gelatin.