Influence of measurement temperature on the rheological and microstructural properties of glucomannan gels with different thermal histories

摘要

Samples of 3% glucomannan gels made with 0.6M KOH and preheated at T ht: 25°C (A), 50°C (B), 70°C (C) and 90°C (D) were studied at two measurement temperatures (T m: 50 and 70°C) and compared to T m: 25°C. Samples B and C were gels more thermo-stable at high measurement temperatures. This means that a preliminary heating at 50 and 70°C would be needed to retain their structural integrity of these gels. When the preheated gels were subjected to high deformation (puncture test), rigidity increased with increasing T m. Similarly, small deformation tests showed that at T m: 50°C and 70°C, the C sample had better gel characteristics than the others: i.e. higher elasticity and lower frequency-dependence of viscoelastic moduli. This means that there was more particle aggregation, so that when gels C were heated they would maintain a high degree of internal cohesion and connectivity. Mechanical and rheological analyses were consistent with the structures shown in SEM photographs. © 2012 Elsevier Ltd.