title: Heat-induced aggregation of whey proteins in aqueous solutions below their isoelectric point.
abstract: Processing beverages containing high concentrations of globular proteins represents a technological challenge due to their instability during heating caused by protein aggregation and gelation. Aggregation of whey protein mixtures was investigated in aqueous model systems at pH 3.5, 4.0, and 4.5 at heating conditions resembling conventional industrial treatment (90 °C for 30 s). The extent of aggregation progressively decreased moving away from the pI. Protein aggregates became smaller and had a more open structure compared to higher pH values. Significant loss of protein dispersibility occurred at pH 4.0 and 4.5 above the denaturation T of whey protein (∼70 °C), at which aggregation was caused by intermolecular hydrophobic interactions. Accessible thiol groups were detected in the heat-treated systems, with a higher intensity at higher pH and increasing extent of aggregation. Intermolecular -S-S- bonding played only a minor role in the aggregation at all conditions studied.
authors.affiliation: Nutricia Research, Uppsalalaan 12, 3584 CT Utrecht, The Netherlands.
authors.forename: Leonardo
authors.initials: L
authors.lastname: Cornacchia
authors.forename: Cécile
authors.initials: C
authors.lastname: Forquenot de la Fortelle
authors.forename: Paul
authors.initials: P
authors.lastname: Venema
mesh_terms: D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D007526:Isoelectric Point; D008894:Milk Proteins / Q000737:chemistry*; D066329:Protein Aggregates; D000067816:Whey Proteins
chemical_list: D008894:Milk Proteins; D066329:Protein Aggregates; D000067816:Whey Proteins
keywords: aggregation; surface hydrophobicity; thiol reactivity; whey protein