Abstract
Chemical modification of casein micelles by succinylation was investigated in order to assess the role of electrostatic charges in both acid and rennet coagulation, as well as to find a relationship between the chemical modification applied and the ability of milk proteins to coagulate. Succinylation of milk resulted in a delay of gelation and in a decrease in the final firmness of a rennet gel. The resistance of casein micelles to aggregation could be explained by the increase in electrostatic repulsion induced by the introduction of additional negative charges to the proteins. Results showed that the changes in the rheological properties upon rennet coagulation could be related to the microstructural differences observed between the succinylated and the reference milk: so changing the balance of protein charges upon decreasing the pHi increased the coagulation time of acid gels, but might also considerably alter the formation of hydrophobic interactions between succinylated casein micelles during the aggregation phenomena in rennet milk gels.