Stability of casein micelles cross-linked with genipin: A physicochemical study as a function of pH
Résumé
Chemical or enzymatic cross-linking of casein micelles (CMs) increases their stability against dissociating
agents. In this paper, a comparative study of stability between native CMs and CMs cross-linked with
genipin (CMs-GP) as a function of pH is described. Stability to temperature and ethanol were investigated
in the pH range 2.0e7.0. The size and the charge (z-potential) of the particles were determined by dynamic
light scattering. Native CMs precipitated below pH 5.5; CMs-GP precipitated from pH 3.5 to 4.5,
whereas no precipitation was observed at pH 2.0e3.0 or pH 4.5e7.0. The isoelectric point of CMs-GP was
determined to be pH 3.7. Highest stability against heat and ethanol was observed for CMs-GP at pH 2,
where visible coagulation was determined only after 800 s at 140 C or 87.5% (v/v) of ethanol. These
results confirmed the hypothesis that cross-linking by GP increased the stability of CMs.