A new method of separating ovomucin from egg white.

Ovomucin, a key component in maintaining the viscous nature of egg white, is a glycoprotein contributing to 2-4% of the total egg albumin protein. Preparation of pure ovomucin remains a challenge due to the presence of coprecipitated proteins, mainly ovalbumin and lysozyme. The objectives of the study were to determine the effect of different salt concentrations on the extractability of ovomucin and to develop a simple method to purify ovomucin that could be adapted for further scale-up production. The protein compositions of ovomucin extracts were significantly affected by salt concentrations. The concentration of ovalbumin was increased, whereas that of lysozyme was decreased in the ovomucin extracts at increasing salt concentrations up to 500 mM; lysozyme was the major contaminant at low salt concentrations (<100 mM), whereas ovalbumin was the major contaminant at high concentrations (>or=200 mM). A 2-step method was developed for the first time to prepare ovomucin with a purity of greater than 90%. Egg white was first extracted in the presence of 100 mM NaCl at pH 6.0 to produce a precipitate containing moderate coprecipitated ovalbumin (14.6%) and lysozyme (15.9%); the contaminated proteins in the precipitate were further removed by using 500 mM NaCl. The yield of ovomucin was determined to be 400.2 mg/100 g of egg white. This 2-step method is simple, environmentally friendly, and easy for scale-up preparation.