Stability of casein micelles cross-linked with genipin: A physicochemical study as a function of pH

Abstract

A B S T R A C TChemical 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 2.0-7.0. The size and the charge (ζ-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 2.0-3.0 or pH 4.5-7.0. 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.

Property changes of caseinate in response to its dityrosine formation induced by horseradish peroxidase, glucose oxidase and d‐glucose

“…29 If caseins were crosslinked by TGase or genipin, they also possessed more negative zeta-potentials. 30,31 Consistent with these previously reported results, both CLCN-I and CLCN-II would have larger particle sizes and more negative zeta-potentials in aqueous medium. As a result of a higher cross-linking extent or higher relative dityrosine content, CLCN-I had more protein polymers than CLCN-II, and therefore showed more property changes.…”

The surface properties of milk fat globules govern their interactions with the caseins: Role of homogenization and pH probed by AFM force spectroscopy

“…similar to that of the casein micelles alone (-15.6 ± 0.9 mV; Table 1). Therefore, the increase in negativity of the homogenized MFG was due to the adsorption of milk proteins, especially the negatively-charged casein micelles [33]. The size distributions and ζ-potential values of native or homogenized MFG after washing did not significantly differ to those of MFG in native or homogenized milk samples (Table 1).…”

Physical Stability and Interfacial Properties of Oil in Water Emulsion Stabilized with Pea Protein and Fish Skin Gelatin

“…where (η) is the viscosity of the solvent, (μ) the electrophoretic mobility, (ε) the dielectric constant of the medium and [f (κR H )], the Henry's function. (κ) is the thickness of the double electric layer or Debye length and R H is the particle radius [30].…”