Changing the isoelectric point of the heat-induced whey protein complexes affects the acid gelation of skim milk

Marion Morand (1) , Fanny Guyomarc'H (1) , David Legland (2) , Marie-Hélène Famelart (1)

1 STLO - Science et Technologie du Lait et de l'Oeuf
2 GMPA - Génie et Microbiologie des Procédés Alimentaires

Heat treatment of milk at 85-95 °C for several minutes increases both the pH of gelation and firmness of acid milk gels, changes usually attributed to the formation of heat-induced whey protein complexes in the milk. To investigate the role of the electrostatic properties of the heat-induced complexes on the acid destabilisation of heated milk, heat-induced whey protein complexes were modified by succinylation or methylation, giving pI values ranging from 3.8 to 5.3, while size, secondary structure, surface hydrophobicity and thiol/disulfide distribution were kept reasonably constant. These complexes were added to whey-protein-free skim milk systems and the resulting acid gelation behaviour of the milk samples was evaluated. The pH of gelation of these milk samples increased significantly as the pI of the complexes increased. This demonstrated both the importance of the complexes in the acid-induced gelation of milk and the relevance of repulsive electrostatic interactions in the acid destabilisation of milk.

Mots clés: protéine laitière;

Domaines: Sciences agricoles

Marion Morand, Fanny Guyomarc'H, David Legland, Marie-Hélène Famelart. Changing the isoelectric point of the heat-induced whey protein complexes affects the acid gelation of skim milk. International Dairy Journal, 2012, 23 (1), pp.9-17. ⟨10.1016/j.idairyj.2011.10.006⟩. ⟨hal-01189599⟩