Rheological properties of selected gum solutions

Gums are integral ingredients in fluid foods used for controlling viscosity and mouthfeel. Advances in rheological instrumentations permits enhanced evaluations of the viscoelastic properties of fluids. Rheological properties of twelve gum solutions were investigated at concentrations of 0.05%, 0.1%, and 0.5%. The viscous (eta") and elastic (eta") components of the complex viscosity, eta*, elastic yield stress, and tan delta were measured as functions of oscillatory shear. Konjac exhibited the highest eta' and eta" components among all gums at 0.5% and 50 s(-1). Gum Arabic, methylcellulose and pectin, exhibited the least eta' and no eta", component under the same conditions. Konjac exhibited greatest elastic yield stress, whereas microcrystallinecellulose had the least. Modeling results showed that rheological properties of CMC were characterized by an exponential relationship, whereas riota-carrageenan and xanthan were described by a power type relationship. A substantial increase in tan delta was observed for most 0.5% gums solutions at shear rates beyond 10 s(-1), indicating a shift from a visco-elastic regime to a purely viscous one. For gums that showed substantial visco-elasticity, peak tan delta values ranged from 5.7 to 68.3. (C) 2004 Elsevier Ltd. All rights reserved.