Small deformation measurements of transient gels using vane rheometry
Published:19 May 2004
I. Ratcliffe, P. A. Williams, R. J. English, and J. Meadows, in Gums and Stabilisers for the Food Industry 12, ed. G. O. Phillips and P. A. Williams, The Royal Society of Chemistry, 2004, pp. 360-367.
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Measurement of a model transient gel system, i.e. pre-gelled borate cross-linked konjac glucomannan (KGM) has been facilitated by the use of a controlled stress rheometer in conjunction with a stainless steel vane geometry. Calibration of the vane was undertaken in both shear flow and oscillation and enabled reproduction of data recorded using traditional cone and plate and couette fixtures. The transient nature of the borate cross-links coupled with the sharp blades of teh vane facilitated ‘healing’ of the gel around the geometry, resulting in minimal disturbance to the gel. Alternative techniques employed to measure these gels include in-situ gelation in a parallel plate geometry. Using this method difficulties in achieving sample homogeneity imposed serious restrictions upon the range of polysaccharide and borate concentrations that could be studied, and long in-situ gelation times were unavoidable. The microstructure of borate cross-linked KGM gels has been investigated by small strain oscillation measurements using the vane and the trends in the network relaxation times with variation in both polysaccharide concentration and borate concentration established.