Characterisation of whey protein isolate-gum tragacanth electrostatic interactions in aqueous solutions

The main objectives of this study were to measure molecular parameters of gum tragacanth by GPC-MALLS system and investigate the complexation behaviour of whey protein isolate/gum tragacanth mixed dispersions (0.5wt% total biopolymer concentration) as a function of pH (7.00-2.00) and the biopolymer mixing ratio (r=0.1-10) using spectrophotometric, zeta potential and precipitate yield determination methods. GPC-MALLS revealed that gum tragacanth contains relatively heterogeneous particles with high weight-average and number-average (M-w=7.74x10(5)gmol(-1) and M-n=3.87x10(5)gmol(-1)) molecular mass and high dispersity index (similar to 2.04 +/- 0.3). Results of complexation displayed that as the biopolymer mixing ratio increases, the net neutrality shifts to the higher pHs. The critical values associated with the complex structure formation were found at r=2 in which the charge density of the mixture was near zero at a wide range of pH (3.0-4.0). However, the highest precipitate yield achieved in pH 3.4.