Thermal denaturation and renaturation of a fermentation broth of xanthan: rheological consequences

Viscosity Behavior of Xanthan Solutions Measured as a Function of Shear Rate

“…The discrepancy between the viscosity data measured at increasing and decreasing shear rates may be due to imperfect sample preparation. However, a viscosity behavior similar to that found in this study has been shown for solutions of xanthan 11,22) , Aureobasidium pullulans cultures 24) , etc. Thus, it is thought that this discrepancy is caused by a structure change inherent in these biological polymer solutions.…”

“…11,22) That is, when the shear rate was increased in the low-shear-rate region, the viscosity increased to a maximum value and then decreased, showing shear thinning behavior. However, the viscosity showed no specific behavior for decreasing shear rates, when the sample experienced a high shear-rate.…”

Rheology of xanthan solutions as a function of temperature, concentration and ionic strength

“…For this reason the dynamic mechanical properties of xanthan in aqueous solution have been investigated extensively (Capron, Brigand, & Muller, 1998;Cuvelier & Launay, 1986;Lee & Brant, 2002;Oviatt & Brant, 1994;Pelletier, Viebke, Meadows, & Williams, 2001;Rochefort & Middleman, 1987;Rodd, Dunstan, & Boger, 2000; Ross-Murphy, Morris, & Morris, 1983;Whitcomb & Macosko, 1978;Wyatt & Liberatore, 2009). For a given temperature the viscosity increases strongly with increasing concentration, while it decreases strongly with increasing temperature especially at low ionic strength.…”

Single Molecules and Networks of Xanthan Gum Probed by Atomic Force Microscopy

“…3a) confirms that heating causes irreversible structural changes. Rheological data recorded during repeated heatingcooling treatments of an aqueous dispersion of xanthan frequently reveal thermal hysteresis only in the first heatingcooling cycle (Oviatt and Brant, 1994;Capron et al, 1998a). It is therefore considered that the initial unheated state differs from the renatured state and that transitions between the denatured and renatured states are thermo-reversible.…”

“…Xanthan molecules are believed to be in the doublestranded helical conformation in the native state, while structural order is lost at temperatures above its conformational transition temperature (T c ) (Morris, 1998). Heat-denatured molecules renature upon cooling to a temperature below T c ; however, an aqueous dispersion of renatured xanthan may exhibit significant increases in viscosity and shear modulus relative to the dispersion prior to heating (Oviatt and Brant, 1994;Capron et al, 1998a). Sato and co-workers recently studied thermal denaturation and renaturation behavior of xanthan using a light scattering technique and revealed that at relatively high xanthan concentrations, the apparent molecular weight in the renatured state can be much larger than that in the native state due to aggregation between multiple molecules occurring during the renaturation process (Matsuda et al, 2010).…”