SYNERGISTIC EFFECTS BETWEEN

XANTHAN GUM AND CASSIA TORA GUM

 

Galactomannans mixed with xanthan gum produce solutions that defy ordinary viscous blending laws. Because of synergistic effects [1] this mixture shows much higher viscosity and elasticity than either component alone. The synergism is a result of the interaction between the ordered region on the xanthan gum molecule and the unsubstituted "smooth" region of the galactomannan [2]. The synergism between xanthan gum and the galactomannan, carboxy methyl cassia tora gum, is profiled here.

Two parent solutions and a mixture of the two were measured. One solution contained xanthan gum (1500 ppm in distilled water) and the other contained carboxy methyl cassia tora (1500 ppm in distilled water). These solutions were mixed in equal parts. The above figures show the loss and storage moduli at 2 Hz and room temperature for the two solutions and their mixture.

The cassia tora only solution has no measurable storage modulus. When the two gums are mixed, a dilatant "bump" is seen in the loss modulus of the xanthan gum-cassia tora mixture that is not present in the component solutions. This loss modulus anomaly does not have a counterpart in the storage modulus.

[1] Kovacs, P. , Useful incompatibility of xanthan gum with galactomannans, Food Technology, 27, 26-30 (1973).
[2] Clarke, M. T., Rheological Additives, in Rheological Properties of Cosmetics and Toiletries, ed. by D. Laba (Marcel Dekker, Inc., New York) 55-152 (1993).

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