Effect of different concentrations of calcium chloride and potassium chloride on egg white proteins during isoelectric precipitation of ovomucin
2009
Omana, D.A. | Wu-O, Jess
The effect of various concentrations of CaCl₂ and KCl on egg white proteins during isoelectric precipitation of ovomucin was investigated in this study. At low concentrations of CaCl₂ (<50 mM), lysozyme was the major contaminant in the precipitated ovomucin, whereas ovalbumin was the predominant one at high concentrations (greater-than-or-equal100 mM). At 50 mM CaCl₂ concentration, the concentrations of both lysozyme and ovalbumin were moderate. Ovomucin with a purity of 97.3% was prepared using a 2-step method: egg white was first precipitated in the presence of 50 mM CaCl₂ followed by a second 500 mM CaCl₂ extraction. The concentrations of other proteins in the precipitate were 1.3% of ovalbumin, 1.1% of lysozyme, and 0.4% of ovomucoid. Unlike CaCl₂-treated samples, ovotransferrin was found to be the second major contaminant in all KCl-treated precipitates. Compared with the control, adding KCl at the lowest concentration of 2.5 mM increased significantly the content of ovalbumin (from 7.6 to 68.0%) and reduced significantly the content of lysozyme (from 25.5 to 6.4%) in the precipitates; however, increasing the concentrations of KCl up to 500 mM did not affect the content of ovalbumin, but the content of lysozyme showed a general reduction trend. Although KCl was used widely in literature as the last step of ovomucin washing, our results show that KCl is not an efficient salt in purifying ovomucin.
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