title: Controlling the Ratio between Native-Like, Non-Native-Like, and Aggregated β-Lactoglobulin after Heat Treatment.
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.
authors.affiliation: Laboratory of Food Chemistry, Wageningen University , Bornse Weilanden 9, 6708 WG Wageningen, The Netherlands.
authors.forename: Roy J B M
authors.initials: RJ
authors.lastname: Delahaije
authors.affiliation: Laboratory of Food Chemistry, Wageningen University , Bornse Weilanden 9, 6708 WG Wageningen, The Netherlands.
authors.forename: Harry
authors.initials: H
authors.lastname: Gruppen
authors.affiliation: Nutricia Research , Uppsalalaan 12, 3584 CT Utrecht, The Netherlands.
authors.forename: Evelien L
authors.initials: EL
authors.lastname: van Eijk van Boxtel
authors.affiliation: Nutricia Research , Uppsalalaan 12, 3584 CT Utrecht, The Netherlands.
authors.forename: Leonardo
authors.initials: L
authors.lastname: Cornacchia
authors.affiliation: Laboratory of Food Chemistry, Wageningen University , Bornse Weilanden 9, 6708 WG Wageningen, The Netherlands.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Wierenga
mesh_terms: D002942:Circular Dichroism; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007782:Lactoglobulins / Q000737:chemistry*; D009994:Osmolar Concentration; D066329:Protein Aggregates; D011489:Protein Denaturation; D017510:Protein Folding
chemical_list: D007782:Lactoglobulins; D066329:Protein Aggregates
keywords: aggregation; concentration; denaturation; ionic strength; pH; refolding; structure; temperature; unfolding