Q. Effect of addition of ingredients on egg foam stability?
The addition of other ingredients also influences stability. Sometimes salt is added to an egg white foam for flavour, but this addition reduces stability slightly. Occasionally recipes include some added liquid in making egg white foam. This dilutes the proteins in the foam and decreases stability. If yolk happens to contaminate the white at all, as can happen during the separation of yolks and whites, stability of the foam formed from the whites is reduced.
Not all ingredients reduce stability. In fact, the addition of sugar has a very laudatory effect on foam stability. A possible explanation is that the addition of sugar delays foam formation significantly, which means that considerably more beating is necessary to reach the proper stage of foam development. This increased beating results in foam with a finer texture and more surface area. This foam is stabilized with protein that has been partially denatured by beating.
Acidic ingredients, commonly either cream of tartar or lemon juice, are useful stabilizing agents when making egg white foams, particularly when added early in the formation of the foam. Although stability is promoted by reducing the pH of the egg white foam, formation of the foam is delayed by this addition. Again, the delay in reaching the desired end point in whipping the foam results in increased total agitation and a finer, more stable foam. Cream of tartar is particularly effective as the acid ingredient when the pH of the white foam approaches pH 6.0, whereas, citric acid and cream of tartar are about comparable in their effect at pH 8.0.