Cold ultrafiltered or microfiltered milk retentates: A systematic comparison of the effects of compositional differences on their gelation functionality

Ozgenur Coskun*, Lars Wiking, Milena Corredig

*Corresponding author for this work

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaperJournal articleResearchpeer-review


The colloidal stability of casein micelles suspensions prepared using ultrafiltration (UF) and microfiltration (MF) was studied by testing acid- and rennet-induced destabilization. Skim milk and 4× (based on volume reduction) concentrates were obtained by processing under similar conditions, at temperatures below 10°C. Concentrates were subjected to different levels of diafiltration (DF), resulting in samples with comparable casein volume fractions but different amounts of proteins and ions in the serum phase. The novelty of the work is the systematic comparison of MF and UF concentrates of similar history. More specifically, concentrates similar in ionic composition but with or without serum proteins were compared, to evaluate whether whey proteins and β-casein depletion from the micelles will play a role in the processing properties, or whether these are affected solely by the ionic balance. Microfiltered micelles' apparent diameter decreased by about 50 nm during the specific hydrolysis of κ-casein by chymosin, whereas those in skim milk control showed a decrease of about half that size. All concentrates subjected to extensive DF showed smaller hydrodynamic diameters, with reductions of ∼18 and 13 nm for MF and UF, respectively. Highly diafiltered UF retentates showed a delayed onset of rennet-induced gelation, due to low colloidal calcium, compared with other samples. Low-diafiltered samples showed weak storage modulus (∼1 Pa) after 60 min of onset of gelation. In addition, onset pH increased with diafiltration to ∼5.8 for UF and ∼6 for MF in high-diafiltered samples. These results clearly demonstrated that the functional properties of casein micelles change during membrane concentration, and this cannot be solely attributed to changes in ionic equilibrium.
Original languageEnglish
JournalJournal of Dairy Science
Pages (from-to)3123-3136
Number of pages14
Publication statusPublished - May 2023


  • casein micelles
  • gelation
  • membrane filtration
  • whey protein depletion
  • Animals
  • Food Handling/methods
  • Micelles
  • Caseins/chemistry
  • Milk/chemistry
  • Milk Proteins/analysis
  • Hydrogen-Ion Concentration

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