Associative Phase Separation in Aqueous Mixtures of β-lactoglobulin and Gum Tragacanth – Whole Gum and the Soluble Fraction of the Gum

The knowledge of non-covalent interactions between proteins and polysaccharides is of the utmost importance in the development of engineered food materials, as the structure, function and stability of these composite food systems are primarily determined by macromolecular interactions. In the present study, electrostatic interactions and the subsequent associative phase separation of total gum tragacanth (TGT) and its soluble fraction, tragacanthin (T), with β-lactoglobulin (BLG) were investigated in aqueous medium as a function of pH (2.00–6.00) using spectrophotometry, light scattering and, in situ and continuous viscosity measurements. The results obtained by these complementary methods, allowed the associative phase separation process to be characterised in terms of five pH-delimited zones at which critical transitions took place. Both mixtures followed a similar trend, suggesting the occurrence of similar mechanism of complexation/ phase separation under our experimental conditions. Some small differences were however noticed. Indeed, the characteristic pH values associated with structural transitions in BLG+TGT mixtures were slightly higher and the kinetic of phase separation was faster. It was found that the assembled structures experience a progressive contraction process upon complexation. Interestingly, complexation of BLG and T at pH 4.30 led to the formation of nano-particles (d <60 nm).

کلیدواژه ها:

Gum Tragacanth ، β-lactoglobulin ، Associative Phase Separation ، Complexation