Characterising the physical state and textural stability of sugar gum pastes

Water sorption and textural properties of four sugar gum pastes were investigated to characterise their physical state and textural stability when exposed to adverse %RH and/or temperature conditions. Dynamic vapour sorption (25 °C) and dynamic dewpoint isotherm (25 and 40 °C) methods showed that all gum pastes exhibit predominantly Type III sorption behaviour due to the presence of large amounts of crystalline sugars. Gum paste deliquescence points (RHo) were influenced by sugar type, with the commercial materials (containing sucrose and glucose) exhibiting lower RHo values than the lab-made materials (containing sucrose); and by storage temperature, with lower RHo values at 40 °C compared to 25 °C. Changes in textural properties (hardness, distance to break, and structural integrity), signifying decreased gum paste stability, occurred concomitantly with the initial stages of increased water sorption, driven mainly by RHo differences among the gum paste materials.