Experimental cookery

Salt and the whipping o£ egg whites. It is traditional that a small amount of salt added to egg white is an aid in increasing foaming and stiffness. This could easily be tested but so far as the writer knows its effect on stability has not been reported. It has been found that electrolytes are necessary for heat coagulation of proteins. They may also aid coagulation by mechanical means or surface denaturation. The more likely explanation is the one previously given for protein solutions and electrolytes. The pro- tein lowers the surface tension but the addition of salt lowers it still more, thus causing a greater concentration of the protein at the air/liquid inter- face, hence a slight stiffening. The addition of salt may result in a slight salting-out effect and a stiffening of the membrane around the air bubbles. This would have the same result as in emulsions. For, by the last mecha- nism a certain amount of salt would bring about maximum stabilization 348 EGG COOKERY of the emulsion or foam, but too large a quantity would have the tendency to break the emulsion or the foam. Acids and stability of egg white foams. Barmore in his last publication states that when acid substances were added in sufficient quan- tity to adjust the egg white to pH 8 the stability of the foam was prac- tically the same for acetic and citric acids and for cream of tartar. But at pH 6 the cream of tartar produced the most stable foam. The acid sub- stances increased the stability of the foams. The addition of the acid delays the formation of the foam, i.e., if beaten for a definite time the foams containing acid are not as stiff as those con- taining no acid. This is particularly true for both acetic and citric acids. The addition of sugar to egg white foams. Adding sugar to the egg white increases the stability of the foam, for less drainage occurs when the egg is beaten to a definite stiffness. However, a longer time is required to beat the egg white, if the sugar is added before the beating is completed, but this also makes it difficult to overheat the foam. Because sugar retards denaturation of the egg white foam, it is a good practice to add sugar to the egg white as soon as beating is started when whites for angel cakes are whipped at high speed on a machine. It would also appear that less leakage might occur in meringues for pies if the sugar is added by beating it into the white as the white is beaten. Egg white is partially coagulated during beating. In whipping the egg white is finely divided, so that from the physical subdivision it is far more rigid and stiff. But the beating has brought about other changes in the egg w^hite. In speaking of the methods by which coagulation may be brought about, Ostwald states, ''When egg white is beaten to a foam, a part is regularly coagulated in the walls enclosing the air bubbles. A decrease in degree of dispersion to the point of inducing coagulation can also be brought about through centrifuging, etc. These belong to the mechanical methods of producing coagulation."