Linear Viscoelastic Properties of Selected Polysaccharide Gums as Function of Concentration, pH, and Temperature

Hydrocolloids have been intensively investigated due to their ability to modify the rheology of the system where they are employed. They find application as thickening and gelling agents in many food, cosmetic, and pharmaceutical preparations, due to their biocompatibility and biodegradability. The present study aims to provide an exhaustive and comprehensive viscoelastic characterization of a series of hydrocolloid formulations, as function of concentration, pH, and temperature. Glucomannan, xanthan gum, tara gum, guar gum, konjac gum, and gellan gum have been analyzed at two concentrations (0.5% w/w and 1.5% w/w), using three different pH conditions (pH 1.2, 5.5, and 6.8). Their viscoelastic properties have been monitored measuring the main rheological parameters, namely, storage modulus G' and loss modulus G'' as function of frequency, time, and temperature. The results obtained show a clear dependence of the linear viscoelastic properties of the systems on concentration and pH, while the temperature was not a critical factor. Glucomannan, xanthan gum, tara gum, and guar gum samples prepared in phosphate buffer (pH 6.8) at the final concentration of 1.5% (w/w) have been selected as the most promising systems for further investigations, exploring the possibility of combinations to improve the rheological properties. PRACTICAL APPLICATION: Glucomannan, xanthan gum, tara gum, guar gum, konjac gum, and gellan gum have been chosen among the most common thickening agents derived from plants to perform a systematic investigation of the influence of pH, concentration, and temperature on the rheological properties of their water dispersions. The data obtained may be useful for further application of these hydrogels in the nutraceutical field as thickeners, texture modifiers, emulsifiers, stabilizers, and gelling agents.