Dynamics of isoelectric precipitation of casein using sulfuric acid

Authors

  • G. W. Hofland,

    Corresponding author
    1. Laboratory for Process Equipment, Delft University of Technology, Delft, The Netherlands
    Current affiliation:
    1. Laboratory for Process Equipment, Delft University of Technology, Leeghwaterstraat 44, 2628 CA Delft, The Netherlands
    • Laboratory for Process Equipment, Delft University of Technology, Leeghwaterstraat 44, 2628 CA Delft, The Netherlands
    Search for more papers by this author
  • M. R. Berkhoff,

    1. Laboratory for Process Equipment, Delft University of Technology, Delft, The Netherlands
    Search for more papers by this author
  • G. J. Witkamp,

    1. Laboratory for Process Equipment, Delft University of Technology, Delft, The Netherlands
    Search for more papers by this author
  • L. A. M. van der Wielen

    1. Kluyver Laboratory for Biotechnology, Delft University of Technology, Delft, The Netherlands
    Search for more papers by this author

Abstract

The acid precipitation of casein from skim milk is an interesting and complex operation, as it involves several mechanistic steps occurring simultaneously. Research has focused so far on the influence of static variables such as temperature and final pH on the curd properties. Here the dynamics of the process was investigated. From a characteristic times analysis it was concluded that the most important mechanistic steps in the acid precipitation of casein were acid mixing, aggregation/breakup, and transport in/out of the precipitate particles. Experiments in a fed batch setup using sulfuric acid as the precipitant showed how the precipitation influenced the pH profile and demonstrated the large influence of process variables, such as the acid addition rate, the mixing intensity, and aging time on particle-size distributions and the release of minerals from the casein.

Ancillary