The physico-chemical properties of chia seed polysaccharide and its microgel dispersion rheology

The polysaccharide gel layer surrounding hydrated chia seeds was extracted using water and isolated by ethanol precipitation. The freeze-dried sample consisted of ∼95% non-starch polysaccharides (35% w/w neutral soluble fraction and 65% w/w negatively charged insoluble fraction). The soluble polysaccharide fraction has molar mass, root-mean square radius and intrinsic viscosity of ∼5 × 105 g/mol, 39 nm and 719 mL/g, respectively. The whole polysaccharide (included soluble and insoluble fractions) when dispersed in water showed presence of irregular shape, fibrous microgel particles with an average size (D4,3) of ∼700 μm. Rheological measurements indicated a 'weak' viscoelastic gel and strong shear dependent properties even at low concentration (0.05% w/w). The viscosity of the dispersion was fairly resistant to variations in temperatures (20-80 °C), pH (4-12), ionic strengths (0.01-0.5 M NaCl) and cation types (MgCl2, CaCl2, NaCl and KCl). The swollen microgel particles dispersed in soluble polysaccharide continuous phase provided complex and potentially useful rheological properties in food systems.