Heat-induced whey protein isolate fibrils: Conversion, hydrolysis, and disulphide bond formation

S.G. Bolder, A. Vasbinder, L.M.C. Sagis, E. van der Linden

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Fibril formation of individual pure whey proteins and whey protein isolate (WPI) was studied. The heat-induced conversion of WPI monomers into fibrils at pH 2 and low ionic strength increased with heating time and protein concentration. Previous studies, using a precipitation method, size-exclusion method, or proton NMR spectroscopy, reported a wide range of values for the conversion. An alternative method was developed, namely centrifugal filtration, giving a consistent picture of the conversion. The present results help to explain the disparities reported in literature. No fibrils formed upon heating pure ¿-lactalbumin or pure BSA at pH 2, whereas fibrils formed in pure ß-lactoglobulin (ß-lg) and WPI solutions. Experiments indicate that ß-lg was the only whey protein involved in fibril formation. In all whey protein samples, hydrolysis occurred during heating at pH 2, as determined by HPLC and SDS-PAGE. When WPI fibrils formed at pH 2 were stored at pH 7 or 10, disulphide bonds were formed in the samples. Keywords: Heat-induced aggregation; Whey proteins; Fibrils; Conversion; HPLC; SDS-PAGE
Original languageEnglish
Pages (from-to)846-853
JournalInternational Dairy Journal
Publication statusPublished - 2007


  • beta-lactoglobulin
  • amyloid fibrils
  • gelation

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