There are several types of omelets. They are designated in various ways as plain, French, and foamy omelets. Some have a white sauce or tapioca basis. In others, bread crumbs are used to absorb a part of the moisture. The type of omelet that has the egg yolk folded into the beaten white is sometimes called a foamy omelet. This is the type that requires the most skill in making and is the one mentioned here.

Method of mixing foamy omelet. The yolk is beaten until foamy and then folded into the stiffly beaten egg white. The cooked omelet should be light, tender, and foamy, and it should not collapse or fall after cooking, though some shrinkage usually occurs. Whether the product obtained fulfils these conditions depends to a great extent upon the amount of beating of the egg white, the mixing of the egg white and the yolk, and a proper cooking temperature. The egg whites for omelets need to be whipped nearly or quite stiff enough to stay in an inverted bowl. Unless they are sufficiently stiff there is a tendency for the liquid to drain to the bottom of the bowl or cooking pan. After the yolks are mixed with the whites this tendency is increased. Sometimes the liquid portion does collect in the bottom of the cooking pan and coagulates there while cooking, forming a thick compact layer. This is due to insufficient beating of the whites, or insufficient mixing of the yolk with the white, so that the yolk is not sufficiently blended through the white to be held up by the framework or physical structure of the whipped white, or it may be due to standing too long after mixing before cooking is started. The pan into which the omelet is poured should be hot enough to start coagulation of the egg, but not hot enough to form a hard crust. However, over-mixing and rough handling cause loss of too large a portion of the air incorporated into the egg white. Over-beating of the egg white before the yolk is added results in loss of extensibility, and the volume of the omelet does not increase as much as it should during baking. It is also drier and sometimes powdery. But with omelets it seems better to err a little on the side of over-beating rather than under-beating.

Formation of ferrous sulfide in omelets. The green color develops on the bottom of the omelet only when some of the egg has separated and drained to the bottom. It is due to the formation of hydrogen sulfide from the white and its combination with iron of the yolk. It may be prevented by sufficient beating of the egg white, by thoroughly blending the yolk and white, or by starting cooking promptly. The color may develop in omelets cooked on top of the stove, or in those cooked in Pyrex, but occurs more often in baked ones, for the baking requires a longer time.

Effect of addition of a liquid to a foamy omelet. A tablespoon of water for each egg is usually added to the white or to the yolk. If to the white of the egg, it may be added before the white is beaten or after it is beaten enough to become frothy but not stiff. The volume of the beaten white with the addition of the liquid is usually greater than an egg white without the added liquid. Sometimes other factors due to size of the egg, its deterioration in quality, or other causes affect its beating qualities and a poor volume is attained. It has already been stated that increasing alkalinity tends to prevent coagulation. Thus very old eggs may not beat as well as fresher ones. The hydration of the white increases the tenderness of the omelet as well as its elasticity. The white being more elastic, a larger volume is obtained during cooking. If too much water is added to the egg a point is reached at which the white becomes too tender and too many cells break when the air expands during cooking. Evidently the addition of water to egg white retards coagulation by beating, for a longer time is required to beat the white to a definite stage than when no liquid is added. This retardation of coagulation may be due to the lessened concentration of the egg white.

Kind of liquid in omelets. The liquid added to foamy omelets may be water, vegetable juice, tomato juice, or a mixture of one-third lemon juice and two-thirds water. If a tablespoon of milk is added to an egg white it will not form a foam. If added to the beaten white the volume is quickly reduced and the foam is destroyed. Dizmang and Sunderlin investigated the effect of milk on the whipping quality of egg white. Their results are given in Table 42, and indicate that the fat of the milk is responsible lor breaking the foam. But the size of the fat globules is also important, smaller particles having less effect.

Table 42 The Effect of Milk on Whipping Quality of Egg Whites

(Dizmang and Sunderlin)

Substance added to egg white

Largest number of drops added to one egg white, permitting formation of foam stiff enough to stay in an inverted bowl

Cream (20% fat)........................

1-2

Whole milk............................

2-3

Sterilized whole milk....................

8

Reconstituted powdered whole milk.......

50-70

Cream (20% fat) homogenized, 3000 lbs. . .

70

Evaporated milk........................

50-350

Separated milk.........................

400-446

Whole milk, homogenized, 2500 lbs........

400-450

Whole milk homogenized at 3000 lbs......

1000

Reconstituted powdered separated milk. . . .

1600

The addition of 1 teaspoon of lemon juice and 2 teaspoons of water to an egg white brings the reaction to about pH 4.8, the isoelectric point of the egg albumin. It may be higher or lower, depending on the original pH and perhaps the size of the egg. The addition of a tablespoon of tomato juice to an egg white does not lower the pH to 4.8. The addition of tomato juice and the lemon juice results in a more tender omelet, and one of greater volume, if the conditions of mixing have been standardized, if the liquid is added after the egg white is partially beaten, and if beaten to the same degree of stiffness. Tomato juice requires longer for whipping than the water, and the mixture of lemon juice and water requires still longer than the tomato juice. The addition of the acid tomato and of the lemon lessens the alkalinity of the egg white. Bogue has reported that the foaming properties of gelatin are greatest at the isoelectric point. If the foaming properties of egg white are also greater at the isoelectric point, a greater volume might be expected at pH 4.8. This greater volume is usually obtained, with the addition of tomato or lemon juice, but a longer whipping time is required. Tomato and lemon both contain citric acid. The greater tenderness with the use of tomato juice and lemon juice probably results from a peptizing effect of the citrate ion on the egg protein. If lemon juice is merely added to egg white without whipping it, coagulation of the egg white is produced, but with beating the lemon juice is thoroughly mixed with the egg white. A better volume is usually obtained if the egg white is beaten until frothy before the lemon juice or tomato juice is added.

Temperature for cooking omelets. Omelets are usually cooked above heat, but baking them in the oven is an easy method to secure uniform temperatures for class work. A temperature of 160° to 165°C. is a good one to use. If the temperature is too low the omelet tends to separate while cooking, the liquid portion collecting in the bottom of the cooking utensil and forming a solid mass with the foamy part on top. Too high a temperature for cooking leaves the inside of the omelet too moist unless the outer portion is over-cooked and thus toughened. In cooking over the heat the omelet needs to be covered. The omelet can be placed under the broiler to brown the top quickly.