Physical and chemical interactions in cold gelation of food proteins

A.C. Alting, H.H.J. de Jongh, R.W. Visschers, J.W.F.A. Simons

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107 Citations (Scopus)

Abstract

pH-Induced cold gelation of whey proteins is a two-step process. After protein aggregates have been prepared by heat treatment, gelation is established at ambient temperature by gradually lowering the pH. To demonstrate the importance of electrostatic interactions between aggregates during this latter process, -lactoglobulin aggregates with a decreased iso-electric point were prepared via succinylation of primary amino groups. The kinetics of pH-induced gelation was affected significantly, with the pH gelation curves shifting to lower pH after succinylation. With increasing modification, the pH of gelation decreased to about 2.5. In contrast, unmodified aggregates gel around pH 5. Increasing the iso-electric point of -lactoglobulin via methylation of carboxylic acid groups resulted in gelation at more alkaline pH values. Comparable results were obtained with whey protein isolate. At low pH disulfide cross-links between modified aggregates were not formed after gelation and the gels displayed both syneresis and spontaneous gel fracture, in this way resembling the morphology of previously characterized thiol-blocked whey protein isolate gels (Alting, et al., J. Agric. Food Chem. 2000, 48, 5001-5007). Our results clearly demonstrate the importance of the net electric charge of the aggregates during pH-induced gelation. In addition, the absence of disulfide bond formation between aggregates during low-pH gelation was demonstrated with the modified aggregates
Original languageEnglish
Pages (from-to)4682-4689
JournalJournal of Agricultural and Food Chemistry
Volume50
Issue number16
DOIs
Publication statusPublished - 2002

Keywords

  • heat-induced aggregation
  • whey-protein
  • beta-lactoglobulin
  • disulfide bonds
  • denatured whey
  • set gels
  • isolate
  • ph

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