High-protein fat-free acid milk gels: Control of protein composition and heat treatment

Skim milk supplemented with calcium caseinate (Ca-Cas) and whey protein isolate (WPI) at different ratios was preheated at 72–90 °C for 7 min and subsequently acidified for the production of set-style and stirred acid gels. Upon heat-treatment of the suspensions, the native whey protein content decreased and particle size increased with increasing temperature and WPI content. Consequently, the pH of gelation, firmness of the set gel, viscosity and particle size of the stirred gel all increased as the content in denatured whey protein increased. However, for preheating temperatures of 80 or 90 °C, the viscosity and firmness of the gels reached a plateau, although almost all whey proteins were denatured and largest particles were formed. These results open perspectives for the production of high-protein yoghurts without unusual firmness properties.