Exothermic events on heating of semi-dilute konjac glucomannan-water systems

Differential scanning calorimetric experiments were designed and conducted to investigate the occurrence of two intriguing exothermic events, hitherto never reported before, on programmed heating of semi-dilute (≤1.0%, w/w) aqueous konjac glucomannan (KGM) solutions to temperatures above 70 °C. These exothermic transitions, with peak temperatures of 74-80 °C and 115-132 °C, respectively, were attributed to disorder-order transitions of different kinds. The results of storage and annealing experiments suggest that these transitions were time-dependent. The ordered structures formed on heating were heat-stable, at least up to 180 °C.