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BY-NC-ND 3.0 license Open Access Published by De Gruyter June 2, 2014

Re-association Behavior of Casein Submicelles in Highly Alkaline Environments

  • Hang Bian and Johann Plank EMAIL logo

Abstract

The pH-dependent dissociation and re-association behavior of casein proteins in alkaline environment was studied. In dilute aqueous solutions of pH = 12 and 13, casein was found to exist in the form of submicelles which represent the fundamental structural unit of casein micelles. Morphology and dimension of the casein submicelles were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM), revealing spherical particles of ~ 10 - 30 nm in diameter. When the pH was increased to 14, unexpected re-association of casein submicelles occurred, resulting in the formation of large network aggregates at pH > 14. Furthermore, calcium phosphate was found to be the main driving force behind the re-association, as verified by comparative experiments employing Ca-depleted casein. Based on an analysis of potential interactions between the proteins, this re-association is ascribed to decreased electrostatic repulsion, strengthened hydrophobic attraction and formation of calcium phosphate linkages between casein proteins.

Graphical Abstract

 
              Re-association Behavior of Casein Submicelles in Highly Alkaline Environments

Re-association Behavior of Casein Submicelles in Highly Alkaline Environments

Received: 2012-02-03
Published Online: 2014-06-02
Published in Print: 2012-06-01

© 1946 – 2014: Verlag der Zeitschrift für Naturforschung

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

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