Moisture-induced quality changes of hen egg white proteins in a protein/water model system

Qinchun Rao, Jeancarlo R. Rocca-Smith, Ted P Labuza

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


In recent years, the intermediate-moisture foods (IMF), such as nutrition and energy bars, are a rapidly growing segment of the global food market. However, due to moisture-induced protein aggregation, commercial high protein nutrition bars generally become harder over time, thus losing product acceptability. In this study, the objectives were to investigate the moisture-induced protein aggregation in a hen egg white proteins/water dough model system (water activity (aw): 0.95) and to evaluate its molecular mechanisms and controlling factors. During storage at three different temperatures (23, 35, and 45 °C) for 70 days, four selected physicochemical changes of the dough system were analyzed: the aw, the color (L* value), the fluorescent Maillard compounds (fluorescence intensity (FI) value), and the remaining free amino groups. Overall, the physicochemical changes of egg white proteins in the dough system are closely related to the glass transition temperature (Tg). The effect of moisture content on both the L* and FI values occurred as a function of storage time at 45 °C due to the Maillard reaction. The change of the remaining free amino groups at different temperatures was derived from the coaction of both the Maillard reaction and enzymatic hydrolysis from molds. Additionally, through analyzing the buffer-soluble egg white proteins using gel electrophoresis, our results showed that moisture-induced aggregates were produced by two chemical reactions during storage: the disulfide interaction and the Maillard reaction. Furthermore, the effect of two processes during manufacturing, desugarization and dry-heat pasteurization, on the physicochemical changes of the egg white proteins was elucidated. In order to prevent or reduce moisture-induced protein aggregation during product storage and distribution, two potential solutions were also discussed.

Original languageEnglish (US)
Pages (from-to)10625-10633
Number of pages9
JournalJournal of agricultural and food chemistry
Issue number42
StatePublished - Oct 24 2012


  • Maillard reaction
  • disulfide interaction
  • hen egg white proteins
  • intermediate-moisture foods
  • moisture content
  • protein aggregation


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