Study On Effects Of Xanthan Gum And Guar Gum On Wheat Starch Properties

The following essay had been studied the impact of xanthan gum(XG)and guar gum(GG)of different concentrations for wheat starch(WG)on the pasting property,rheological property,retrogradation and freeze-thaw stability.The result of experiment was shown as follows:After adding the xanthan gum and guar gum,both of the gelatinization's initial temperatures and gelatinization's peak temperatures dropped for wheat starch,while the peak viscosity increased.The xanthan gum had no obvious impact on the final viscosity of the wheat starch,while the guar gum increased its Final Viscosity.As the viscosity of colloid rose,The WS/XG blends and WS/GG blends' amylose dissolution quantity,swelling capacity and iodine-binding capacity increased.The guar gum could more substantially improve the dissolution quantity of amylase than the xanthan gum.The adding of xanthan gum and guar gum could substantially suppress the rebirth of wheat starch,largely improving the transparency of the wheat starch in the long time storage.The effect of guar gum was better than the xanthan gum to inhibit rebirth of starch.However,when colloid concentration reached 3%,the effect had no significant change.The result of the steady state rheology showed that both the wheat starch and its blend system belonged to pseudoplasticity flow and that xanthan gum and guar gum increased the apparent viscosity(?a,100)and the consistency coefficient(K)of the wheat starch paste,decreasing the fluid index(n)of wheat starch.The blend system had a higher pseudoplasticity and liquidity,on which the guar gum had a better effect than the xanthan gum.The fact that both two colloids could decrease the activation energy of wheat starch could explain that the adding of these two hydrocolloids could decrease the sensitivity to the temperature of wheat starch paste.The dynamic rheology showed that the xanthan gum and guar gum changed the parameter of the wheat starch dynamic rheology and decreased the storage modulus(G')and loss modulus(G'')of the wheat starch.But both the loss angle and tangent value(tan?)of the blend system were larger than that of the wheat starch,and the integrative viscosity of blend system increased too.The water syneresis rate of the wheat starch was enhanced with increasing freeze-thaw cycle number,and xanthan gum and guar gum added could significantly decrease the water syneresis rate,besides inhibiting wheat starch aging during the freeze-thaw process.Additionally,the improvements in freeze-thaw stability were more significant with increasing hydrocolloid concentrations.After five wheat starch freeze-thaw cycles,a large number of holes were formed in the starch gum matrix,and some discontinuous silk-and fiber-like structures were formed,with a thin substrate.With the addition of hydrocolloids,the apparent structure of wheat starch changed: the number of holes decreased,the starch substrate was thickened,and a sheet-like network structure was formed.