The formation of electrostatic complexes between sodium caseinate and gum tragacanth (Astragalus
gossypinus, A.g) as a function of pH (7.00e2.50), the biopolymer mixing ratio and the total biopolymer
concentration was studied by spectrophotometric and light scattering measurements.
This multi-methodological approach allowed us to demonstrate the critical structure-forming pHs
associated with the formation of soluble and insoluble complexes for the sodium caseinate/A.g mixture.
The phase transition of sodium caseinate/A.g complexed/coacervated system was explained by monitoring
the absorbance profiles as a function of time.
Particle size measurements revealed a progressive decrease in the complex/aggregate size while
lowering the pH until reaching a minimum (pH 4) at which nanoparticles (70 nm) formed.
As the mixing ratio of protein to polysaccharide increased from 1:1 to 3:1, the critical pHs shifted
towards higher pH values. Conversely, for a constant mixing ratio, higher levels of total concentration
resulted in an increase in the maximum turbidity but had no meaningful effect on pHC (w5.89) and pHF1
(w4.00).