Solubilization of rehydrated frozen highly concentrated micellar casein for use in liquid food applications

Y. Lu, D. J. McMahon, L. E. Metzger, A. Kommineni, A. H. Vollmer

Research output: Contribution to journalArticlepeer-review

34 Scopus citations


Highly concentrated micellar casein concentrate (HC-MCC), a potential ingredient of protein-fortified food, is a gel at cold temperature. It contains ~17 to 21% casein, with most serum proteins and lactose removed by microfiltration and diafiltration, and it is then further concentrated using vacuum evaporation. The HC-MCC can be stored frozen, and our objective was to determine the conditions needed to obtain complete solubility of thawed HC-MCC in water and to understand its gelation upon cooling. Dispersibility (ability to pass through a 250-μm mesh sieve), suspendability (percentage of protein not sedimented at 80 × g within 5. min), and solubility (percentage of protein not sedimented at 20,000 × g within 5. min) were measured at 4, 12, or 20°C after various mixing conditions. Gelation upon cooling from 50 to 5°C was monitored based on storage (G') and loss (G'') moduli. The gelled HC-MCC was also examined by transmission electron microscopy. Thawed HC-MCC was added to water to reach a protein concentration of 3% and mixed using high shear (7,500. rpm) for 1. min or low shear (800. rpm) for 30. min at 4, 12, 20, or 50°C and at pH 6.4 to 7.2. The HC-MCC completely dispersed at 50°C, or at ≤20°C followed by overnight storage at 4°C. Suspendability at 50°C was ~90% whereas mixing at ≤20°C followed by overnight storage resulted in only ~57% suspendability. Solubility followed a similar trend with ~83% at 50°C and only ~29% at ≤20°C. Mixing HC-MCC with 60. m. M trisodium citrate increased dispersibility to 99% and suspendability and solubility to 81% at 20°C. Cold-gelling temperature, defined as the temperature at which G'. =. G'' when cooling from 50 to 5°C, was positively correlated with protein level in HC-MCC. Gelation occurred at 38, 28, and 7°C with 23, 20, and 17% of protein, respectively. Gelation was reversible upon heating, although after a second cooling cycle the HC-MCC gel had lower G'. In micrographs of gelled HC-MCC, the casein micelles were observed to be within the normal size range but packed very closely together, with only ~20 to 50 nm of space between them. We proposed that cold-gelation of HC-MCC occurs when the kinetic energy of the casein micelles is sufficiently reduced to inhibit their mobility in relation to adjacent casein micelles. Understanding solubilization of rehydrated frozen HC-MCC and its rheological properties can help in designing process systems for using HC-MCC as a potential ingredient in liquid food.

Original languageEnglish (US)
Pages (from-to)5917-5930
Number of pages14
JournalJournal of Dairy Science
Issue number9
StatePublished - Sep 1 2015

Bibliographical note

Funding Information:
We thank Nabil N. Youssef (Utah State University) for suggestions on transmission electron microscope sample preparation and comments on manuscript, Silvana Martini (Utah State University) for her assistance and advice in rheological measurements, the Aggie Creamery (Utah State University, Logan) for donating of cream and its staff for help with protein measurements, and the Electron Microscopy Core Research Facility at the University of Utah (Salt Lake City) for use of the transmission electron microscope. Funding for this research was provided by the National Dairy Council (Rosemont, IL), and the Utah Agricultural Experiment Station, Utah State University, and approved as journal paper number 8767. The use of trade names in this publication does not imply endorsement by Utah State University of the products named nor criticism of similar ones not mentioned.

Publisher Copyright:
© 2015 American Dairy Science Association.


  • Micellar casein
  • Microfiltration
  • Solubility


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