EFFECTS OF GALACTOMANNAN ADDITION ON RHEOLOGICAL, PASTING AND PHYSICAL PROPERTIES OF WATER CHESTNUT STARCH

This study investigated the effects of galactomannans (guar gum, tara gum and locust bean gum) on the rheological, pasting and physical properties of water chestnut starch. All water chestnut starch-galactomannan mixtures (0.5% w/w) had significantly higher shear-thinning fluid characteristics than the control (0% gum). Adding all of galactomannans significantly increased the values of apparent viscosity ((a,100)), consistency index (K) and yield stress (sigma(oc)) for water chestnut starch. In the dynamic rheological analysis, the dynamic moduli (G, G) and complex viscosity (*) for water chestnut starch-galactomannan mixtures were significantly greater than those for the control. The water chestnut starch-guar gum mixture in particular had significantly higher viscoelastic properties compared with the starch-tara gum or starch-locust bean gum mixtures. The incorporation of all galactomannans increased the peak viscosity and gel strength, but decreased the syneresis values of water chestnut starch. The guar mixtures seemed to be the most stable over freeze-thaw cycles. Practical ApplicationsMixed starch and gum gels are gaining popularity in the food industry. This study elucidated the effects of galactomannans (guar gum, tara gum and locust bean gum) on the rheological, pasting and physical properties of water chestnut starch. The results indicated that galactommanns can be used as a thickener for improving the rheological properties of water chestnut starch and stabilizer for reducing the syneresis of the starch during freezing-thaw cycles in the food industry. Furthermore, galactomannans can be used to enhance the physical and pasting properties of water chestnut starch-based food products.