Stabilization of Oil-in-water emulsions by β-lactoglobulin-polyethylene glycol conjugates

Document Type

Article

Publication Date

2-27-2002

Abstract

The disulfide bonds of β-lactoglobulin (β-lg) were modified by oxidative sulfitolysis to generate β-lgSO3. The native protein β-lg) and the modified protein (β-lgSO3) were conjugated to activated polyethylene glycol (PEG) to generate β-lgPEG and β-lgSO3PEG; respectively. Oil-in-water (o/w) emulsions containing 1% β-lg or β-lg conjugates were prepared at pH 2.8, 5.0, and 7.0. Emulsion droplet diameters and zeta potentials were measured. For the same emulsifier, emulsion droplet diameters decreased when emulsion pH increased. Zeta potentials of emulsion droplets increased with pH for β-lg and β-lgSO3. Zeta potentials of β-lgPEG and β-lgSO3PEG approached zero, suggesting that the protein molecule was covered by PEG chains. Accelerated and 7-day storage stabilities at 21°C of the emulsions were monitored. The emulsifying activity index (EAI) of β-lgPEG was not significantly different from the EAI of βlg. The EAI of β-lg was enhanced following sulfitolysis of β-lactoglobulin. The emulsifying activity increased more when the oxidatively modified protein was conjugated to polyethylene glycol. Emulsions made with β-lgSO3PEG were more stable than emulsions made with β-1g, β-lgPEG, or β-lgSO3 under accelerated stability study and for 7 days at 21°C. The stability of o/w emulsions stabilized with β-lgSO3PEG increased because individual droplets were better protected, against protein bridging or coalescence, by the thick adsorbed protein-PEG layer.

Publication Source (Journal or Book title)

Journal of Agricultural and Food Chemistry

First Page

1207

Last Page

1212

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