The Key Egg White Proteins Involved in Foam Formation and Foam Stability.

This study determined the major egg white proteins for foaming and foam stability. The natural and lysozyme-free egg whites were 2x diluted and blended with a KitchenAid blender for 5 minutes to make foams. The foams were collected, held at room temperature for 2 hr, and drained. Samples were collected 5 minutes after blending and 2 hr after foam collection. The forming and sampling processes were repeated 2 more times after putting the drain back into the residual egg white. The proteins in the samples were separated using SDS-PAGE, the proportion of each band was calculated, and the proteins in the band were identified using tandem mass spectrometry. Ovotransferrin, ovalbumin, and ovomucoid were the three main proteins for foaming. The proportions of ovomucin, ovomacroglobulin, ovalbumin-related protein Y, TENP proteins, clusterin and ovalbumin fragments, avidin, and lysozyme were either dramatically increased or newly appeared in the foams after 2 hr of holding, indicating they were the main proteins for foam stability. The contributions of ovalbumin, ovotransferrin, and ovomucoid to foam stability were smaller than their proportions in the egg white. The dried weight of the first foam from natural egg white was twice as high, but that of the ovomucin-rich fraction was half of the lysozyme-free egg white due to the formation of ovomucin-lysozyme complexes in the egg foams. It was concluded that the solubility, formation of complexes, fragmentation, and polymerization of proteins were important for foam stability.