Attractive interactions between selected anionic exopolysaccharides and milk proteins

Interactions between bacterial exopolysaccharides (EPS) and milk proteins are believed to influence the texture of fermented milk. In this work, interactions between five anionic EPS and milk proteins have been studied using titration and centrifugation. Attractive interaction of EPS with caseins and with whey proteins (WPI) was initiated at pH 5.4 and 6.1, respectively. Under interacting conditions, the solubility of caseins was only slightly influenced by EPS whereas the solubility of WPI depended strongly on EPS added. Charge density was the main factor influencing the amount of EPS complexed onto casein molecules, while their molecular weight, chain stiffness, and charge density were all structural features influencing their binding onto WPI. The study of interactions between negatively charged EPS and milk proteins will give an insight into the modulation of the texture of fermented milk.