Sorption of Water Vapor, Hydration, and Viscosity of Carboxymethylhydroxypropyl Guar, Diutan, and Xanthan Gums, and Their Molecular Association with and without Salts (NaCl, CaCl₂, HCOOK, CH₃COONa, (NH₄)₂SO₄ and MgSO₄) in Aqueous Solution

Abstract

Gums are routinely used in food industry, pharmacy and oil recovery process. In these uses, the hydrocolloids very often encounter interactions with salts at moderate to high temperature. Since they are normally employed in the form of solution and gel, their viscous or fluidity properties need detailed investigation. In the present work, properties such as water vapor adsorption of finely powdered carboxymethylhydroxypropyl derivatized guar (CMHPG) as well as xanthan (Xn) and diutan (Dn) gums, their hydration in solution, their viscosity behaviors, and salt effects on fluidity have been studied. The concentration domains for the existence of free and associated molecules in the studied solutions have been assessed from the viscosity results. The gums have been found to bind a fair amount of water from the vapor phase with them. In solution, they can interact and arrest a large amount of water in their folded configuration. Intrinsic viscosities of the gums in aqueous medium declined in the presence of salts. The activation energies for their viscous flow were moderate and comparable, and were dependent on their concentrations. From the power law relation and viscosity master curve behavior mostly two critical association states of the macromolecular dispersions were envisaged.

Rheological properties and thickening mechanism of aqueous diutan gum solution: Effects of temperature and salts

“…Diutan gum is a natural high molecular weight microbial polysaccharide, secreted by the bacterium Sphingomonas sp. It is an anionic biopolymer and consists of a repeat unit with ␤-1,3-d-glucopyranosyl, ␤-1,4-d-glucuronopyranosyl, ␤-1,4-d-glucopyranosyl, and ␣-1,4-l-rhamnopyranosyl, and a twosaccharide L-rhamnopyranosyl side-chain attached to the (1 → 4) linked glucopyranosyl residue (Banerjee et al, 2009;Mohammed & Denis, 2008). Diutan gum acts as a thickening, suspending, binding, emulsifying, and stabilizing agent.…”

Intrinsic viscosity and rheological properties of natural and substituted guar gums in seawater

“…The [Á] in deionized water can be determined by measuring the viscosity of solutions at low concentrations and extrapolating to an infinite dilution solution, according to the Huggins equation, which was used to obtain the [Á] of CMHPG in pure water with good correlations [6].…”

“…The intrinsic viscosity [Á] in seawater can be determined by Eq. (2) known as Higiro et al's equation, which has been found to determine the [Á] of aqueous gums solutions in the presence of salt with good correlations [6].…”

“…Due to the strong electrolyte nature of the applied conditions, the effects of salt on the rheological properties of guar gum have been studied since the 2000s [5][6][7][8][9]. For natural guar gum, a higher apparent viscosity is observed when adding a NaCl/CaCl 2 mixture to a guar gum solution because the shielding of ionic charges formed by salt ions is disrupted, the main chains may be free to expand and hence the viscosity may increase.…”

“…According to the literature, monovalent and bivalent cations produce a screening effect that reduces the segmental repulsions to yield a relatively compact configuration and hence a reduction in the intrinsic viscosity [Á] of CMHPG, and the effect of bivalent cations has been reported to be greater [6]. Hence, the rheological properties of guar gum and its derivatives are worth further investigation for applications in industry.…”