The Rheological Characteristics And Application Of Xanthan Gum And Its Hydrocolloids Mixtures

Xanthan gum is an extracellular polymer produced mainly by the bacterium Xanthomonas campestris.Traditionally it plays an important role in food industrial applications as thickener and emulsion stabilizer.In this paper,xanthan gum's rheological properties and the characteristics of mixtures with other hydrocolloids,and their applications in sponge cake and lactic acid bacteria beverage were studied.The research provided theoretical guidance for the applications of xanthan gum in bakery products and milk beverage.First of all,the rheological behavior,synergistic properties and intermolecular interaction microstructure of xanthan gum and hydrocolloids mixtures were investigated.The results showed that xanthan gum solutions had obvious characteristic of shear thinning.And the xanthan gum solution had higher storage modulus(G')than loss modulus(G").The xanthan gum was mixed with carboxymethyl cellulose sodium(CMC),sodium alginate and guar gum at different ratios.The rheological properties of mixed hydrocolloids solutions were changed after they combined.For xanthan/CMC and xanthan/sodium alginate mixtures,the apparent viscosity of solutions increased with the increasing concentration of xanthan.The apparent viscosity of xanthan/guar mixture solutions were changed sharply due to different mixing ratios.Meanwhile all of the solutions showed typical pseudoplasticity and viscoelasticity of mixed gums were higher than the component gum.For transparent xanthan/guar mixture solution with a ratio of 5/5.its storage modulus(G')and loss modulus(G”)increased significantly,showing a strong synergistic interactions on viscosity and elasticity.The microstructures of transparent xanthan gum and guar gum were tangled and disordered according to SEM images.As for their mixture,the surface of molecular chain structure was flaky and layered regularly.Thus the combined gums formed significant gel network microstructure well,which was consistent with rheological characteristics exhibited.Secondly,based on the rheological properties of transparent xanthan gum and sodium alginate,the study applied them in sponge cake to improve the physical properties,textural and sensory characteristics.The effect of two gums in sponge cake were evaluated by response surface methodology(RSM).According to the significant regression models(p ?0.05),xanthan significantly increased moisture content and sensory acceptability.Sodium alginate had positive effects on specific volume,springiness(p ? 0.05).Hence both gums improved the baking quality of sponge cakes(p ? 0.05),and augmented the potential for using them in cake.Based on RSM optimization,a balance between amounts of transparent xanthan(0.307%)and sodium alginate(0.248%)led to make products with desired physical properties and acceptable sensory quality.Finally,the effects of xanthan,CMC and guar on physical properties and sensory quality of lactic acid bacteria beverage were studied by RSM.The results showed that optimal mixed gums(transparent xanthan 0.153%,guar 0.057%,CMC 0.154%)improved the centrifugal sedimentation rate to 90?95%and kept apparent viscosity at 290?300 cP.The gums not only improved the stability of products,but also increased the persistence of beverage flavor release,provided soft taste.Thus gums improved the quality of the beverage,which provided potential choice for developing better stabilizer in milk beverage.