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

•Isolated chia seed polysaccharide consisted of insoluble and soluble fractions.•Higher proportion of insoluble (65%) to soluble (35%) polysaccharide fractions.•Insoluble fraction consists of fibrous, swollen gel particles (D4,3 ∼700μm).•Rheological tests showed ‘weak gel’ properties and strong pseudoplasticity.•Gel dispersion rheology was relatively insensitive to salt, pH and temperature. 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 ∼5×105g/mol, 39nm and 719mL/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 ∼700μm. 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 (0.01–0.5M 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.