Flow Properties of Selected Food Gums

Abstract

The flow properties of aqueous solutions of the food gums furcellaran, guar and xanthan were studied. The study was conducted with a concentric cylinder viscometer over the approximate shear rate range of 50 to 700 s-1, and the temperature range of 25 to 45°C. The ranges of concentrations (w/w, %) employed for the gums were: furcellaran, 0.5 to 1.6%; guar, 0.5 to 2.0%; and xanthan, 0.5 to 1.2%. Time-dependent shear thinning (thixotropic) behavior was noted in the case of furcellaran solutions (0.8 and 1.2%), and shear thinning (pseudoplastic) behavior alone with xanthan and guar solutions. The power law model τ = kγn and the general Casson flow model τA-τ0A = kγA,A<1 were employed to describe the flow behavior. For furcellaran solutions, both the power law and the Casson models were satisfactory for describing the flow behavior. For xanthan and guar gum solutions, the power law model described the flow model over a wide but not the entire range of shear rates, while the general Casson model was satisfactory for the lower concentration solutions. Except at low concentrations* the effect of temperature on the apparent viscosity (at 100 and 500 s-1) was found to be small for all the gums.