Complex formation between Tragacanth gum and beta-lactoglobulin in aqueous solution

Proteins and polysaccharides are common ingredients in food products. In many food formulations, proteins and polysaccharides (two major biopolymers) are used simultaneously. Understanding their interactions can help controlling physical properties and stability of formulated foods. Interactions between β-lactoglobulin (BLG) and tragacanth gum (TG) were studied in aqueous solutions at pH ranging from 3.5 to 5.5 and at different biopolymers concentrations. BLG and TG solutions were prepared in distilled water under gentle stirring at 20°C. Different biopolymers concentrations were mixed and pH value were adjusted by HCl. Absorbance of the mixtures were measured at 650 nm using UV-Visible spectrophotometer. The measured absorbances were plotted against pH. In this study, pHC, pHφ, and pHopt were identified and measured for different biopolymers concentrations. Phase separation observed during experiments is an associative phase separation. Complex sizes increased between pHC and pHφ because of soluble complexes formation and then a decrease in complex sizes was observed and this decrease was due to neutralization of initiate complexes and solubilization of biopolymers complexes. This wide range of complex formation helps product developer to use tragacanth gum in a large range of formulations.