Complex coacervates of lactotransferrin and β-lactoglobulin

Skelte G. Anema*, C de Kruif

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review


Hypothesis: Oppositely charged proteins should interact and form complex coacervates or precipitates at the correct mixing ratios and under defined pH conditions. Experiments: The cationic protein lactotransferrin (LF) was mixed with the anionic protein β-lactoglobulin (B-Lg) at a range of pH and mixing ratios. Complexation was monitored through turbidity and zeta potential measurements. Findings: Complexation between LF and B-Lg did occur and complex coacervates were formed. This behaviour for globular proteins is rare. The charge ratio's of LF:B-Lg varies with pH due to changing (de) protonation of the proteins. Nevertheless we found that the complexes have a constant stoichiometry LF:B-Lg=1:3 at all pH's, due to charge regularization. At the turbidity maximum the zeta potential of complexes is close to zero, indicating charge neutrality; this is required when the complexes form a new concentrated liquid phase, as this must be electrically neutral. Complexes were formed in pH region 5-7.3. On addition of salt (NaCl) complexation is diminished and disappears at a salt concentration of about 100mMol. The coacervate phase has a very viscous consistency. If we consider the proteins as colloidal particles then the formed complex coacervate phase may have a structure that resembles a molten salt comparable to, for example, AlCl3.

Original languageEnglish
Pages (from-to)214-220
Number of pages7
JournalJournal of Colloid and Interface Science
Publication statusPublished - 15 Sept 2014


  • Complex coacervation
  • Lactoferrin
  • Lactotransferrin
  • Molten salt structure
  • PH
  • β-Lactoglobulin


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