Gelation characteristics of acid-hydrolyzed oat beta-glucan solutions solubilized at a range of temperatures

It has been observed that under certain conditions, acid-hydrolyzed oat (1–3)(1–4)-β-d-glucan (β-glucan) solutions will form gels. However, the optimum conditions for gelation have not been fully explored. In the current work, one of the factors involved in determining gel integrity, initial solubilization temperature, was investigated. Six percent dispersions of two samples of acid-hydrolyzed oat β-glucan of medium and low viscosity (Mw =70,000 and 40,000 g/mol, respectively), were solubilized at 60, 70, 80 and 90 °C for 3 h with constant stirring. After solubilization, the samples were cooled to 25 °C and rheological measurements in flow mode showed that the viscosity decreased with increasing solubilization temperature. Size exclusion chromatography indicated that the decrease in viscosity resulted from better dispersion of aggregates rather than depolymerization. Solutions dissolved at higher temperatures gelled more slowly at 4 °C and had a lower storage modulus after 4 and 7 days. The lower molecular weight sample gelled more quickly and had a higher storage modulus after 4 and 7 days than the higher molecular weight sample. Thus, solubilizing acid-hydrolyzed oat β-glucan solutions at higher temperatures tend to more fully disperse the gum and disrupt small aggregates which may act as nucleation sites for gel formation.