Engineering of heat-induced milk protein particles for acid gels
Résumé
The heat-treatment of skim milk at 90◦C/10 min has long been reported to improve its acid gelation; hence its wide application in yoghurt manufacture. These changes have been attributed to the formation of heat-induced whey protein/kappa-casein complexes that interact with the casein micelles on heating, or shortly on acidification. Through this interaction, the complexes are believed to functionalize the casein micelles as to provoke their early destabilisation on acidification, to increase their bridging connectivity and to enhance their ability to engage stronger interactions on formation of the network. However, the exact nature of the colloidal attractive/repulsive interaction forces that drive gelation and are affected by the complexes is not known. In the seek for a comprehensive view of the acid gelation process in heated milk, a range of artificial protein complexes were produced, having one candidate property largely modulated. The success of the modification was assessed through the complete characterisation of the artificial complexes. The complexes were then introduced into a model milk system, and the acid gelation of these systems was studied. Examples are shown on repulsive electrostatic and attractive hydrophobic interactions