Controlling the ratio between native-like, non-native-like, and aggregated β-lactoglobulin after heat treatment

Roy J.B.M. Delahaije, Harry Gruppen, Evelien L. Van Eijk-Van Boxtel, Leonardo Cornacchia, Peter A. Wierenga*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

16 Citations (Scopus)

Abstract

The amount of heat-denatured whey protein is typically determined by pH 4.6 precipitation. Using this method, a significant amount of nondenatured protein was reported even after long heating times. Apparently, a fraction of the unfolded protein refolds into the "native" state rather than form aggregates. This fact is known and has been explained using kinetic models. How the conditions affect the refolding and aggregation is, however, not fully understood. Therefore, this study investigates the unfolding, refolding, and aggregation process of β-lactoglobulin using circular dichroism and size-exclusion chromatography to characterize different folding variants and to quantify their content. The proteins remaining in solution at pH 4.6 were confirmed to be native-like. The nonaggregated fraction contains proteins with a native-like and two types of non-native-like conformations. The nonaggregated fraction increased with decreasing temperature (60-90 °C) and concentration (1-50 g/L) and increasing electrostatic repulsion (pH 7-8; 0-50 mM). The native-like fraction in the nonaggregated fraction was independent of pH, ionic strength, and concentration but increased with decreasing temperature.

Original languageEnglish
Pages (from-to)4362-4370
JournalJournal of Agricultural and Food Chemistry
Volume64
Issue number21
DOIs
Publication statusPublished - 1 Jun 2016

Keywords

  • aggregation
  • concentration
  • denaturation
  • ionic strength
  • pH
  • refolding
  • structure
  • temperature
  • unfolding

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