Effect of κ-Casein Dissociation from Casein Micelles on Rennet-Induced Gelation in Reconstituted Skim Milk Powder

Abstract

　In this study, we characterized rennet-induced gelation of reconstituted skim milk powder subjected to different heating levels in terms of protein denaturation, including dissociation of κ-casein from casein micelles. The gelation behavior of skim milk powder was evaluated by observing the change in particle size via dynamic light scattering during the rennet reaction in casein micelles. Skim milk powder with a higher degree of heat denaturation was showed the rennet-induced aggregation of casein micelles was strongly inhibited. We characterized κ-casein dissociation from casein micelles, which are factors inhibiting rennet-induced gelation. In the skim milk powder with a higher degree of heat denaturation, κ-casein dissociation was significantly increased than skim milk powder with lower degree of heat denaturation. These results suggest that κ-casein dissociation reduced the formation of para-κ-casein on the micellar surfaces, which impaired casein micelle aggregation. Therefore, it is important to select skim milk powder with a low degree of κ-casein dissociation from casein micelles for cheese production. Overall, the study provides useful data on the use of skim milk powder for cheese production.