Particle and matrix gels of gellan gum: effects of filler particles on rheological properties of matrix gels

The effects of particle gels (PG) on rheological properties of gellan gum gels were studied as a function of PG ratio by measuring the stress–strain curves, dynamic viscoelasticity, syneresis and by the sensory evaluation. Matrix gel (MG) used in the experiments was 0.6 wt% gellan gum gel added with 5 mM CaCl2 (MG(0.6%–5 mM)) or 0.8 wt% gel added with 5 mM CaCl2 (MG(0.8%–5 mM)). MG(0.6%–5 mM) was filled with particle gels of 0.6 wt% gellan gum added with 5 mM CaCl2 (PG(0.6%–5 mM)) or with 2 mM CaCl2 (PG(0.6%–2 mM)). MG(0.8%–5 mM) was filled with PG(0.8%–5 mM) or PG(0.8%–2 mM). Breaking stress, breaking strain, breaking energy and dynamic viscoelasticity of all kinds of gels containing PG decreased with increasing PG content. The sample size dependence of breaking stress of gels containing PG was more intense than that of gels without PG. These results may indicate that particle gels act as inactive filler in the matrix gel. Storage Youngʹs modulus of MG(0.8%–5 mM) without PG increased with increasing temperature from 10 to 40°C and then decreased with further temperature increase to 60°C. The degree of variations of storage Youngʹs modulus with temperature reduced, as the PG content increased. The degree of syneresis increased with an increase in the PG content during storage for 5 h. Gels were identified as soft, brittle, rough and not elastic with an increase in the PG content by the sensory evaluation.