Egg Foams
NAME________________
PERIOD________
Read the following information then answer the questions at the end.
A foam is formed when air is beaten into egg whites. The egg white surrounds the air bubble in the foam. Egg
whites foams are used in puffy omelets, soufflés, meringues, angel cakes, and in other foods. These foods use
the egg foam as a leavening agent. The air in the egg white foams will expand when it is heated and causes the
batter or omelet to increase in volume until the heat coagulates the egg protein which surrounds the air bubble.
This will give a light, porous structure to the product. Low temperatures delay coagulation of the egg white so
that it can stretch with the expanding air and increase in volume. Egg yolk and whole egg will also form foams,
but the volume is much less than the foam of beaten egg whites.
Several things can affect the amount of air that can be beaten into egg whites: (1) egg whites at room
temperature beat more quickly than those at refrigerator temperatures and give a larger volume. So after
separating the whites from the yolks, allow the whites to stand at room temperature for about 30 minutes
before beating so they will reach their fullest volume; (2) fat from any source interferes with the whipping of
egg whites. Fat from the yolk, milk, or a greasy bowl or beaters will reduce the air which egg whites can retain.
So break and separate eggs one at a time, making sure that no yolks get into the whites; (3) a bowl with a small
rounded bottom and sides that slope out to a wider top permits eggs to beat to a better volume. The beater
should fit the bottom of the bowl and the size of the bowl should suit the amount of egg white.
For the best leavening action, the egg white should form a stable foam. A stable foam is one in which little
liquid separates on standing. Some factors which influence the stability of the foam are: (1) cream of tartar
added to egg white makes a more stable foam, although some recipes call for lemon juice or vinegar: (2) thick
whites form more stable foams than thin whites; (3) sugar increases stability but delays foam formation so that
more beating will be required. It is usually best to beat the egg white to a soft-peak stage and then to add the
sugar gradually.
The stiffness to which egg white is beaten is very important. After a little beating, the egg white looks frothy
with large air bubbles on the surface. As beating is continued, the air cells become smaller, the foam becomes
stiffer and is white in appearance. The egg whites are suitable for folding into mixtures when the peak will just
bend over as the beater is slowly lifted out of the foam. This is soft-peak stage is also used for the beating of
soft meringues which are to be spread on various kinds of cream pies. When beating egg whites, they are
classified in three stages according to the peaks the form when the beater is lifted: soft, firm, and stiff peaks.
Additional beating will cause the peak to stand up straight as the beater is lifted forming firm to stiff
peaks. A stiff foam is difficult to fold into other ingredients. Hard meringues are beaten to stiff-peak stage.
Overbeaten egg whites take on a dry appearance, and will eventually collapse and break into pieces, and are not
useful in food preparation.
Hard and soft meringues are egg white foam to which sugar is added. When sugar is beaten into egg whites, it
dissolves into water that is carried along the strands of protein. This is why you add sugar very slowly to give it
a chance to go into solution. If all the sugar doesn’t dissolve, tiny droplets of sugar syrup will form on the
surface of the finished product. The syrup is referred to as “weeping”.
Soft meringues are used as toppings for pies and as ingredients in fruit whips and other desserts. The foam
for hard meringues is beaten to the stiff-peak stage and contains twice as much sugar as the soft meringues.
Hard meringues may be shaped into meringue shells or cookies and baked at a low temperature – (250 degrees).
Meringue shells filled with ice cream and fruit are a very special treat. The most critical factor in making
meringue is humidity. Because of its high sugar content, meringue can absorb moisture from the air and become
limp and sticky. For best results, make meringue on a bright, dry day.
Eggs are susceptible to salmonella contamination that can cause food borne illness. Thorough cooking eliminates
the direct threat (avoid raw eggs). The threat of cross-contamination remains if people handle contaminated
eggs and then touch other foods or items in the kitchen, thus spreading the bacteria.
Salmonella will not grow significantly at a temperature below 4 degrees C and is killed at 60 degrees C.
1. How is egg foam formed?
2. List at least three foods that use egg foam.
3. Egg foams are used as a _________ agent. When the air in the egg foam is heated it _________ which
increases the volume of the food.
4. List three things that affect the amount of air that you can beat into egg whites.
5. List three things that influence the stability of the egg foam.
6. How is sugar added to egg whites when making egg foams?
7. List three ways to prevent salmonella contamination.
Match the word with the letter of the correct description:
_____Leavening Agent
_____Salmonella
_____Meringue
_____Soft Peak
_____Cross-Contamination
_____Stiff Peak
_____Weeping
A. A bacteria that can cause food borne illness
B. A beaten egg white foam that stands up straight when the beaters are lifted.
C. A beaten egg white foam that bends over when the beaters are lifted.
D. The movement of chemicals or microorganisms from one place to another.
E. If sugar is not dissolved into the egg white liquid, tiny droplets of sugar syrup form on the surface.
F. A mixture of sugar and stiffly beaten egg whites.
G. A substance that causes a baked good to rise by introducing gas that expands when heated.