Interaction between the galactomannan from Mimosa scabrella and milk proteins

The rheological properties of mixtures of the galactomannan (G) from Mimosa scabrella Bentham and skim milk (SM), whole milk (WM) and skim milk powder (SMP), sodium caseinate (NaC) and purified casein fractions were investigated. The viscosity curves for the mixtures showed a pseudoplastic behavior, suggesting a protein–polysaccharide synergy, which was more pronounced on increase of polymer concentration. The oscillatory experiments showed a weak gel or concentrated solution behavior at 25 °C, while the properties of the galactomannan in aqueous solution showed a typical liquid-like behavior. Creep and recovery tests for the mixtures confirmed the above results. Rheological measurements of galactomannan and mixtures of it with SM in temperature cycles (10–75–10 °C) showed a maximum in G′ with G′/G″=2.8 at ≈65 °C. These phenomena can be explained by a modification of intermolecular network that became stronger with increase of thermal energy, induced by the galactomannan. However, after cooling at 25 °C, a more viscoelastic material was obtained. Moreover, the galactomannan–NaC mixture showed a synergy effect, observed also for the mixtures with casein fractions in the order β, κ and α-casein. The synergy mechanism of galactomannan and casein fractions may involve phase separation, but electrostatic and/or hydrophobic interactions cannot be discarded.