Influence of pH and Ionic Environment on Thermal Aggregation of Whey Proteins

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A solution of whey protein isolate (WPI) was heated at 1.6 °C/min from 25 to 96 °C to monitor proteinprotein aggregation by turbidity measurement. Protein aggregation showed a single transition (71 °C) at pH 5.5, two transitions (76 and 88 °C) at pH 6.0, and no transition above pH 6.5. The addition of 0.6 M NaCl induced a second transition (77 °C) at pH 5.5 and promoted protein-protein interaction above pH 6.5. The aggregation temperatures decreased to a minimum by 20 mM NaCl and 5-10 mM CaCl2-Protein-protein interaction was suppressed at 5 mM sodium phosphate and gradually recovered at increasing sodium phosphate concentrations. In conclusion, low ionic strengths of cations and low pH facilitated protein-protein association, while phosphate promoted protein aggregation only in conjunction with NaCl.

Original languageEnglish
Pages (from-to)380-384
Number of pages5
JournalJournal of Agricultural and Food Chemistry
Issue number3
StatePublished - Mar 1 1992

ASJC Scopus subject areas

  • General Chemistry
  • General Agricultural and Biological Sciences


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