Molecular interactions between gelatin and mucin: Phase behaviour, thermodynamics and rheological studies

This work studies the interactions, thermodynamics, phase behaviour, and rheology of mucin/gelatin binary mixtures. Addition of gelatin in mucin solutions at pH 7 leads to aggregation and phase separation, while such phenomena are not observed at lower pH values. Zeta potential measurements show that electrostatic interactions lead to the formation of soluble complexes between the mucin and gelatin at pH 3. However, steric exclusions are the prime candidates for inducing any interactions between the two macromolecular populations at pH 7. Fluorimetry shows two binding regimes for mucin/gelatin mixtures at pH 3, and one at pH 7. Delta G show higher negative value at pH 7, as compared to pH 3; this can account for the tendency of gelatin to flocculate in the presence of mucin at neutral environments but not in acidic ones. The Trouton ratio (ratio of extensional to shear viscosity) is low at pH 3, but unusually high at pH 7 due to the aggregated structures. The above highlight the molecular events leading to the flow of gelatin-based foods during oral processing.