Effect of ionic strength, pH and temperature on the behaviour of re-dispersed BC:CMC - A comparative study with xanthan gum

Abstract

The rheological performance of bacterial cellulose and carboxymethyl cellulose (BC:CMC) dry formulations with mass ratios of 1:1, 1:0.75 and 1:0.5 was compared with that of a commercial xanthan gum. The zero-shear viscosity and the yield stress of these hydrocolloids, at concentrations ranging from 0.001% to 0.5% (w/w), were determined by fitting the Cross and Herschel-Bulkley models to the flow curves. Only BC:CMC formulations presented a measurable yield stress, the highest value (1.54 ± 0.17 Pa) being obtained for the 1:0.5 ratio at a concentration of 0.5%. This formulation also presented the highest values of dynamic moduli, namely G′, indicating a stronger solid-like character. Contrarily to xanthan gum, BC:CMC formulations' viscosity profile in aqueous solution was not considerably affected by the pH (in the range from 2.8 to 10.4), the ionic strength (NaCl from 0 mM to 350 mM) or the temperature (6–80 °C). Food grade sunflower oil-in-water emulsions (20% oil) were prepared with 0.3% of the test hydrocolloids, with 150 mM NaCl and pH 3.5. Emulsions with BC:CMC in the ratios of 1:0.75 and 1:0.5 had smaller droplets, stronger solid-like behaviour and resisted centrifugation with little phase separation. These results confirm the high performance of the dry BC:CMC formulations in the stabilization of colloidal systems. • Dry formulations of bacterial cellulose and carboxymethyl cellulose in different mass ratios were prepared. • Higher fibre content in the formulations results in improved rheological properties. • BC:CMC's viscosity is not significantly affected by changes in pH, ionic strength or temperature. • BC:CMC may offer competitive advantages over xanthan gum in the stabilization of food emulsions.