Influence of Grewia polysaccharides on the stability of oil-in-water emulsions

The aqueous dispersion of the polysaccharide isolated from the inner bark of the stem of Grewia mollis exhibits a relatively high viscosity at low concentrations. Two extraction methods were adopted to isolate two different polysaccharide fractions from the plant – the native grewia polysaccharide gum (GPG) and the starch-free grewia polysaccharide (SFGP). The influence of these polysaccharides on the stability of oil – in – water emulsions was investigated at three concentrations – 0.5%, 1.0% and 1.5% w/v. The formulated emulsions were evaluated using parameters such as emulsion stability, storage stability, creaming index, heat stability, globule size and size distribution, and emulsion rheology. The results show that the GPG formulated emulsions were more stable than the SFGP emulsions at each parity level of concentration, exhibiting better emulsion/storage stability, lower creaming index and finer microstructure which were concentration dependent. The higher degree of esterification of SFGP did not result in corresponding improvement in emulsion stability over GPG-containing emulsions. GPG may be preferable to SFGP when stabilization of oil-in-water emulsions is indicated.