Gelation of skim milk containing anionic exopolysaccharides and recovery of texture after shearing

This work aimed to understand the role of the negative charge of exopolysaccharides on milk gelation and on the recovery of the texture of gels after shearing. Purified and well-characterized anionic exopolysaccharides were added to skim milk prior to gelation. The kinetics of gelation and the behaviour of milk gels at large deformation and after shearing were determined using dynamic rheology. Milk gels containing exopolysaccharides having a high net negative charge, a high molecular weight and sulphate groups had a shorter time and higher pH of gelation. This early gelation was attributed to depletion interactions due to non-adsorbed molecules of exopolysaccharide onto casein close to neutral pH, which increased casein–casein interactions. As the pH decreased, attractive interactions between anionic exopolysaccharides and positively charged casein may have influenced milk gelation. The negatively charged exopolysaccharides gave stronger and more brittle milk gels with poor recovering capacity after shearing.