Egg cookery

The yolk is well-centered in the albumen and is
surrounded by the vitelline membrane, which is
colorless.
The germinal disc, where fertilization takes place, is
attached to the yolk. On opposite sides of the yolk are
two, twisted, whitish cord-like objects known as
chalazae.
Their function is to support the yolk in the center of the
albumen.
Chalazae may vary in size and density, but do not affect
either cooking performance or nutritional value.
A large portion of the albumen is thick. Surrounding the
albumen are two shell membranes and the shell itself.
The shell contains several thousand pores that permit
the egg to "breathe."

An average-sized egg weighs approximately 57 grams (about 2
ounces). Of this weight, the shell constitutes 11 percent; the
white, 58 percent; and the yolk, 31 percent. Normally, these
proportions do not vary appreciably for small or large eggs.
The percentage composition of the edible portions is:
Percent water protein fat ash
Whole egg 74 13 11 1
White 88 11 .. ..
Yolk 48 17 33 1

A: Evaluation of egg quality:
Commercial evaluation
Evaluation for Research process
B: changes in egg quality during storage

 1. Commercial Evaluation:
 Eggs are sold commercially according to weight and grade, factors that are independent of
each other.
 The weight of eggs for the purpose of size classification is expressed in ounces per dozen: a
minimum of 15 for pewee, 18 for small, 21 for medium, 24 for large, 27 for extra large, and 30
for jumbo eggs.
 The quality of an egg is determined by evaluating a number of factors. The final score given to
an egg can be no higher than the lowest score given to the egg for any one quality factor.
 Interior quality is evaluated commercially by candling, where the condition of the egg is judged
as it is held up to a light in a dark room and rotated. The candling light reveals the condition
of the shell, the size of the air cell, and the size, distinctness, color, and mobility of the yolk.

2. Evaluation for Research Purposes:
 Several evaluation methods depend on measurement of the
height of the thick white, which can be measured with a
commercially available micrometer attached to a tripod or with
the probe of a vernier caliper.
 The Haugh unit, which indicates the relationship of the height
of the thick white to the weight of the egg, is the most widely
used measure of albumen quality.
 For experimental work it may be desirable to determine the
relative proportions of thick, thin, and adhering albumen. The
eggs are cracked and allowed to drain for 30 sec, after which
the albumen adhering to the shell can be removed.

B. Changes in Egg Quality during Storage:
Temperature:
As soon as the egg is laid, changes begin to take place that lower its quality and
eventually cause spoilage. These changes can be retarded by proper handling,
but they cannot be prevented entirely. During aging, the size of the air cell in-
creases, the yolk enlarges and its membrane weakens, the egg white becomes
thinner, the egg becomes more alkaline, and the odor and flavor of the egg
deteriorate. All of the changes are influenced by temperature. As temperature of
storage increases, the rate of quality loss also increases. Thus, cold storage (—
1.1 -0°C and relatively high humidity) sometimes is used to maintain quality for
long periods of time. For general storage, temperatures of less than 10°C are
Recommended.
Size:
The increase in size of the air cell during storage is commercially important
because it affects the appearance of eggs in candling. The air cell formed after
the egg is laid continues to enlarge as water evaporates from the egg during
storage. Moisture loss is retarded by storing the eggs at a relative humidity of
75-80%

pH:
The pH of the egg white rises with the loss of carbon dioxide from the egg
from about 7.9-8.1 to about 9.1-9.3 in the first 5 days of storage. Changes
in
pH influence the functional properties of egg white. In contrast, yolk pH
changes little from the 6.0 of a fresh yolk during storage.
Odors and flavors:
Some deterioration in odor and flavor occurs during storage of eggs.
Unpleasant flavors are absorbed by eggs if care is not taken to prevent
odors in storage areas. In cold storage, grade A quality can be maintained
for as long as 6 months. Storage of eggs at room temperature may cause a
decrease

FUNCTIONALITY OF EGGS AND THEIR ROLES IN
PRODUCTS:
Coagulation:
Coagulation is a term used to describe that entire process that results in a loss of solubility or a change
from a fluid to a more solid state. The term gelation, meaning the formation of a gel, also is used to
designate the loss of fluidity of egg white and yolk. The coagulation of eggs is responsible for the thickening
effect that eggs have in products such as custards. Egg white begins to thicken as the temperature reaches
62°C, and at 65°C it will not flow. At 70°C the mass is fairly firm. Yolk coagulates at a somewhat higher
temperature than white. It begins to thicken at 65°C and loses its fluidity at about 70°C. Coagulation does
not occur instantaneously but gradually over a period of time. The reaction proceeds more rapidly as the
temperature of heating is increased.
Using scanning electron microscope, seen the changes that occurred in the microstructure of heated
albumen and yolk. The microstructure of albumen gels heated at various temperatures for varying periods
of time.

B. Emulsification:
Egg yolk, which is itself an emulsion, is a good emulsifying agent for
fats or oils and water. It performs this function in many foods,
including shortened cakes, salad dressing, and mayonnaise. The
emulsifying qualities of eggs often are studied in mayonnaise because
it is a relatively simple system.
In mayonnaise, particles of yolk interact at the surface of oil droplets
to form a layer that protects the emulsion by inhibiting coalescence of
the oil droplets. Participants in the layer include both low and high-
density lipoproteins.
C. Foaming:
The foaming of egg whites is important in many foods, because it
makes the products light in texture and contributes leavening. Egg
white foam is a colloidal suspension consisting of bubbles
surrounded by albumen that has undergone some denaturation at
the liquid-air interfaces. This denaturation, which is caused by the
drying and stretching during beating, makes some of the albumen
insoluble, thus stiffening and stabilizing the foam.

 Sunny side up:
An egg fried on one side only.
 Basted egg:
An egg fried on one side with hot grease spooned over the top.
 Over easy:
Eggs fried on both sides with a runny yolk.
 Over hard:
An egg fried on both sides with a hard yolk.
 Poached eggs:
Raw egg cooked in hot water or in egg poacher.
 Shirred eggs:
Raw egg baked in the oven.
 Scrambled eggs:
Egg and milk mixture cooked in a hot pan, gently move mixture as it cooks.
 Hard cooked eggs:
Whole egg cooked in SIMMERING water for twenty minutes.

 Processed eggs are marketed as refrigerated, dried, and frozen eggs and egg
products for use in the food industry and in quantity food production. Research has
led to the development of new processing techniques and the adoption of
regulations to ensure the safety of processed egg products.
 To extend shelf life eggs may be dehydrated, frozen, incorporated into egg substitute
products, or frozen as prepared products.
 A. Dehydrated Eggs:
Spray drying is the most commonly used method for drying whole eggs, egg yolks, or
egg whites. The eggs are preheated to 60°C, then sprayed into a drying chamber
through which air between 121 and 149°C is passing.
An alternative technique used for whites is pan drying. A flake like product (12-16%
moisture) results when whites are dried on pans in an air oven.
heat coagulation properties of eggs are not affected by appropriate drying and
subsequent storage. Scrambled eggs from spray-dried, foam-spray-dried, and freeze-
dried eggs did not differwith respect to tenderness

 B. Frozen Eggs
Freezing effectively preserves the quality of eggs. Whites may be frozen without
any addition, but 10% sugar or 10% salt usually is added to yolks before
freezing so that they will be free from gummy or lumpy particles when they
thaw. The increased viscosity or gelation of frozen yolks after thawing most
likely is due to aggregation of the lipoproteins of yolk to form a network capable
of entrapping large quantities of water. To minimize color changes in
scrambled eggs from frozen mixes, the pH of the whole frozen eggs may be
adjusted from 7.6 to 6.8.
 C. Egg Substitutes
Several investigators have studied the quality of products made from selected
egg substitutes. These products usually contain a high proportion of egg
albumen but contain no yolk. Fat-soluble nutrients are provided by product
fortification. "Scratch" cakes containing substitutes were lower in volume and
rated lower in flavor than those containing the whole eggs

 Development of cooked-frozen egg products that may or may not need heating
after thawing. A problem associated with the freezing of cooked eggs is that
the white becomes tough and rubbery. The problem may be solved with the
addition of a water-binding additive such as carrageenan or starch. These
ingredients are used in the production of the cooked egg roll or "long egg." A
hollow cylinder of cooked egg white is formed and then filled with yolk. The
roll then is cooked and frozen.
 Rapid freezing may help to minimize the problem by limiting damage to the
product by ice crystals. changes in formulation make possible the production
of frozen-cooked egg products that will be acceptable upon thawing and
reheating.

 Coating agent (fresh toast, fried chicken)
 Thickening agent (pudding, custard)
 Binding agent (chicken croquettes)
 Leavening agent (cakes)
 Emulsifier (mayonnaise)

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