Kinetic aspects of casein micelle cross-linking by transglutaminase at different volume fractions

Norbert Raak, Milena Corredig

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Milk protein concentrates (MPC) are widespread food ingredients, due to their high protein-to-solids ratio, nutritional value, and technological properties, which can be tailored to various end uses. Interest has been given to modifying such ingredients through enzymatic cross-linking by microbial transglutaminase. However, no systematic studies on the cross-linking kinetics of casein micelles at different concentration factors are currently available, although the enzyme might act in a considerably different fashion at decreased inter-particle distances. In this study, cross-linking of casein micelles was studied in a 4x MPC obtained by ultrafiltration, and compared to that of the original skim milk. The cross-linking kinetics were evaluated by following the degree of casein polymerisation using size exclusion chromatography. The extent of polymerisation for both skim milk and 4x MPC could be scaled to a master curve by normalising the incubation time to concentration factor and enzyme level, indicating similar cross-linking kinetics. Likewise, the cross-linking of individual casein types followed the same trend regardless of treatment. However, the casein micelle size increased with cross-linking at 4x but decreased at 1x concentration, suggesting enhanced cross-linking on the surface of the casein micelles in MPC suspensions. These results are relevant for the design of novel milk protein ingredients.

Original languageEnglish
Article number107603
JournalFood Hydrocolloids
Number of pages8
Publication statusPublished - Jul 2022


  • Casein micelle
  • Cross-linking
  • Membrane filtration
  • Milk protein concentrate
  • Reaction kinetics
  • Transglutaminase


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