Effect of pH on flow behavior of milk protein–soluble fraction of Iranian native gums (Persian or tragacanth) complexes

Charged polysaccharides can link to negatively charged proteins via electrostatic interaction which prevent aggregation and precipitation of proteins at isoelectric pH. However, attachment of proteins and polysaccharides either may lead to formation of soluble complexes or cause coacervation. Therefore, in the present study, the appropriate ratios of milk proteins–soluble fraction of Iranian native gums to formation of soluble complexes over a wide range of pH (2–6) were investigated. Besides, the effect of pH variation (2, 3, 4, 5 and 6) on the rheological properties of complexes was studied. Based on our results, the appropriate ratio of soluble complex formation for sodium caseinate–soluble fraction of Persian gum, sodium caseinate–soluble fraction of tragacanth, whey protein isolate–soluble fraction of Persian gum, and whey protein isolate–soluble fraction of tragacanth were 0.4:0.6, 0.4:0.6, 0.4:2 and 0.4:1%, respectively. Furthermore, it was observed that whole samples exhibited shear thinning behavior (except the samples contained Persian gum at pH 2 and 3). Moreover, appropriate rheological model for milk proteins–soluble fraction of tragacanth was Power law, independent of pH and gum concentration; whereas, pH and the concentration of gum affected the flow behavior of soluble fraction of milk protein–Persian gum complexes

کلیدواژه ها:

Gum tragacanth ، Persian gum ، Rheology ، Protein–polysaccharide complex