Rheology and microstructure of galactomannan–xanthan gum systems at different pH values

摘要

pH is a significant parameter influencing the performance of biopolymer solution fluids. The rheological properties, structural strength, viscoelastic properties of xanthan gum-galactomannan solutions were largely depended on the pH values. The present research aims to determine the effect of pH on galactomannan-xanthan gum blends. For the sample solutions, an apparent viscosity-increasing effect was explicitly observed over the pH range from 2.0 to 6.0, and the consistency coefficient values gradually decreased at pH 2.0. TheG ' values of the samples which contained the same ratio of hydrocolloid with different pH values were 1.03, 3.43, 13.98 Pa and G '' values were 1.15, 1.29, and 2.99 Pa, respectively. Optimization results represented that the best galactomannan type is tara gum prepared at pH 2.0, tara gum and LBG at pH 4.0. For the solutions prepared at pH 6.0, the optimum results were obtained with the LBG compared with the three studied galactomannan-xanthan gum solution. By optical microscopy, the particle morphology of solutions was different from each other at optimum concentrations and pH. These findings indicate that conditions for providing certain viscoelastic attributes of xanthan-galactomannan dispersions for the purpose of particular applications by careful control of pH. Practical Applications Xanthan gum and galactomannan combinations found many applications in various food products such as ready-to-use dessert soups and salad dressing. There was a research gap to find the optimum xanthan gum and galactomannan combinations along with different pH. The present study investigated the effect of pH on steady and dynamic rheological properties of xanthan gum-galactomannan mixtures. Optimization study was conducted and compared with different pH. Obtained results of current study highlighted the importance of determining the pH for food formulation because they can be used to alter the rheology of food matrices and to get a deeper knowledge on the effects of the pH on the morphology of the system. The present study makes several noteworthy contributions to the rheological characteristics of galactomannan containing food products. These findings indicate that conditions for providing certain viscoelastic attributes of xanthan-galactomannan dispersions for the purpose of particular applications by careful control of pH.