Thermal aggregation properties of whey protein glycated with various saccharides

Aggregation of whey proteins during thermal processing is a challenge to maintain the dispersibility, particularly at pH near isoelectric point and increased ionic strength. We report glycation of whey protein isolate (WPI) with lactose and maltodextrin enabled transparent dispersions after heating at 88 degrees C for 2 min, when tested at 7% w/v protein, pH 3.0-7.0 and 0-150 mM NaCl or CaCl2. Transparent dispersions corresponded to particles smaller than 14 nm based on atomic force microscopy. In comparison, WPI glycated with glucose behaved similarly to WPI control, forming turbid dispersions or gels at many conditions. Based on analytical ultracentrifugation, reducing saccharide with a smaller molecular weight was glycated at a larger number on each protein molecule, agreeing with changes in amino acid composition. Glycation lowered the isoelectric point and increased denaturation temperatures of WPI. The results suggest that repulsive steric interactions are the dominant mechanism controlling whey protein aggregation and thus transparency of dispersions. (C) 2012 Elsevier Ltd. All rights reserved.