Heat Stability of Aggregated Particles of Casein Micelles and κ‐Carrageenan

Aggregated particles of casein micelles and κ‐carrageenan were produced as a dried milk ingredient, then reconstituted and subjected to a heat treatment of 70 °C for 10 min. The reconstituted aggregates were found to be unstable when heated. Light scattering results showed that the aggregates dissociated partially into casein micelles. It was hypothesized that the removal of ions during ultrafiltration before spray‐drying to produce the powdered ingredient significantly decreased stability upon reconstitution and heat treatment. When ions, either from whey permeate or calcium addition, were added to reconstituted aggregates, stability was greatly enhanced and the aggregates remained intact when subjected to heat. The effect of heat treatment on aggregates freshly produced with skim milk powder and κ‐carrageenan was also studied. These aggregates were found to be stable during heating due to the unchanged ionic environment. Therefore, incorporation of powdered aggregates of casein micelles and κ‐carrageenan into products would require the addition of whey permeate or calcium after reconstitution for stability during subsequent heating. Practical Application: Casein micelles and κ‐carrageenan readily form aggregates when cooled together in solution with shearing. These aggregates have the potential to add functionality to skim milk powder; however, they have to be stable to subsequent applications. This research demonstrates that careful control of ionic balance is required to dry the aggregates, reconstitute them, and heat the reconstituted solution to pasteurization temperatures, but when controlled the intact aggregates can be maintained.