title: Complexation of sodium caseinate with gum tragacanth: Effect of various species and rheology of coacervates.
abstract: We investigated complex coacervation of sodium caseinate/Astragalus rahensis (A.r) as a function of pH with light scattering, spectrophotometry, and viscosity measurements. Interestingly, sodium caseinate/A.r displayed five structural transitions; pH 7.00 to pH ∼5.40: no interaction occurred, pH ∼5.40 to pH ∼4.80: initiation of the formation of primary soluble complexes, pH ∼4.80 to ∼4.30: formation of interpolymer complexes, pH ∼4.30 to ∼4.02: optimum coacervation and pH ∼4.02 to ∼2.50: suppression of coacervation. In addition, rheological properties of sodium caseinate/A.r coacervates were studied at various pH values. A much higher storage modulus (G') than loss modulus (G″) for all sodium caseinate/A.r coacervates suggests the formation of highly interconnected gel-like network structures with mainly elastic behaviour. Moreover, sodium caseinate/A.r coacervates at all pH values exhibited a shear thinning behaviour across the entire shear rate range investigated. Effects of different species of gum tragacanth on the interactions with sodium caseinate have been scarcely studied. Our study showed that systems containing various species (A.r, soluble fraction of A.r and Astragalus gossypinus (A.g)) had different critical pH values and particle sizes during complex coacervation, which could be due to different ratio of soluble to insoluble fractions and uronic acid content of various species.
authors.affiliation: Department of Food Science and Technology, National Nutrition and Food Technology Research Institute, Faculty of Nutrition Sciences and Food Technology, Shahid Beheshti University of Medical Sciences, 193954741 Tehran, Iran. Electronic address: sarah.ghorbani@gmail.com.
authors.forename: Sara
authors.initials: S
authors.lastname: Ghorbani Gorji
authors.affiliation: Department of Food Science and Technology, University of Natural Resources and Life Sciences, Vienna (BOKU), Muthgasse 18, Vienna A-1190, Austria. Electronic address: elham.ghorbani-gorji@boku.ac.at.
authors.forename: Elham
authors.initials: E
authors.lastname: Ghorbani Gorji
authors.affiliation: Department of Food Science and Technology, National Nutrition and Food Technology Research Institute, Faculty of Nutrition Sciences and Food Technology, Shahid Beheshti University of Medical Sciences, 193954741 Tehran, Iran. Electronic address: mohamdif@ut.ac.ir.
authors.forename: Mohammad Amin
authors.initials: MA
authors.lastname: Mohammadifar
authors.affiliation: Department of Food Science and Technology, National Nutrition and Food Technology Research Institute, Faculty of Nutrition Sciences and Food Technology, Shahid Beheshti University of Medical Sciences, 193954741 Tehran, Iran. Electronic address: zargaraan@sbmu.ac.ir.
authors.forename: Azizollaah
authors.initials: A
authors.lastname: Zargaraan
mesh_terms: D027883:Astragalus Plant / Q000737:chemistry*; D002364:Caseins / Q000737:chemistry*; D005782:Gels / Q000737:chemistry*; D006170:Gum Arabic / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D010316:Particle Size; D044367:Phase Transition; D012212:Rheology; D014574:Uronic Acids / Q000737:chemistry; D014783:Viscosity
chemical_list: D002364:Caseins; D005782:Gels; D014574:Uronic Acids; D006170:Gum Arabic
keywords: Gum tragacanth; Particle size; Protein–polysaccharide coacervate; Rheological property; Sodium caseinate