Q: What causes blood spots?
A: Small spots of blood (sometimes called "meat"
spots) are occasionally found in an egg yolk. These do not
indicate fertile egg; they are caused by the rupture of a
blood vessel on the yolk surface during formation of the egg.
Most eggs with blood spots are removed during the grading
process but a few may escape detection. As an egg ages, water
moves from the albumen into the yolk, diluting the blood spot.
Thus, a visible blood spot actually indicates a fresh egg.
Such eggs are suitable for consumption. The spot can be removed
with the tip of a knife, if you wish.
Q: Why do some hard-cooked eggs have a greenish ring
around the yolk?
A: The harmless greenish ring is due to an iron and sulfur
compound which forms when eggs are overcooked or not cooled
quickly.
Egg shell and yolk color may vary, but color has nothing to
do with egg quality, flavor, nutritive value, cooking characteristics
or shell thickness.
*Shell: The color comes from pigments in
the outer layer of the shell and may range from white to deep
brown, depending on the breed of hen. Breeds with white feathers
and ear lobes lay white eggs; breeds with red feathers and
ear lobes lay brown eggs. The Rhode Island Red, New Hampshire
and Plymouth Rock are breeds that lay brown eggs. Since brown-egg
layers are slightly larger birds and require more food, brown
eggs are usually more expensive than white.
*White: Egg albumen in raw eggs is opalescent
and does not appear white until it is beaten or cooked. A
yellow or greenish cast in raw white may indicate the presence
of riboflavin. Cloudiness of the raw white is due to the presence
of carbon dioxide, which has not had time to escape through
the shell and thus indicates a very fresh egg. On very rare
occasions, a hard-cooked egg white may darken to a caramel
shade due to a high amount of iron in the cooking water or
to a carbonylamine-type reaction. Using fresh eggs and cooling
them quickly after cooking helps to prevent this darkening.
*Yolk: Yolk color depends on the diet of the hen.
If she gets plenty of yellow-orange plant pigments known as
xanthophylls, they will be deposited in the yolk. Hens fed
mashes containing yellow corn and alfalfa meal lay eggs with
medium yellow yolks, while those eating wheat or barley yield
lighter-colored yolks. A colorless diet, such as white cornmeal
produces almost colorless yolks. Natural yellow-orange substances
such as marigold petals may be added to light-colored feeds
to enhance yolk color. Artificial color additives are not
permitted.
Sometimes there is a greenish ring around hard-cooked egg
yolks. It is the result of sulfur and iron compounds in the
egg reacting at the surface of the yolk. It may occur when
eggs are overcooked or when there is a high amount of iron
in the cooking water. Although the color may be a bit unappealing,
the eggs are still wholesome and nutritious and their flavor
is unaffected. Greenish yolks can best be avoided by using
the proper cooking time and temperature and by rapidly cooling
the cooked eggs.
Occasionally several concentric green rings may be seen in
hard-cooked egg yolks. A yolk develops within the hen in rings.
Iron in the hen's feed or water as the rings are formed may
cause this coloring.
Sometimes a large batch of scrambled eggs may turn green due
to a chemical change brought on by heat and occurs when eggs
are cooked at too high a temperature, held for too long, or
both. Although not pretty, the color change is harmless. Using
stainless steel equipment and low cooking temperature, cooking
in small batches and serving as soon as possible after cooking
will help to prevent this. If it is necessary to hold scrambled
eggs for a short time before serving, it helps to avoid direct
heat. Place a pan of hot water between the pan of eggs and
the heat source.
The yolk or yellow portion makes up about 33 percent of the
liquid weight of the egg. It contains all of the fat in the
egg and a little less than half of the protein.
With the exception of riboflavin and niacin, the yolk contains
a higher proportion of the egg's vitamins than the white.
All of the egg's vitamins A, D and E are in the yolk. Egg
yolks are one of the few foods naturally containing vitamin
D.
The yolk also contains more phosphorus, manganese, iron, iodine,
copper, and calcium than the white, and it contains all of
the zinc. The yolk of a Large egg contains about 59 calories.
Double-yolked eggs are often produced by young hens whose
egg production cycles are not yet completely synchronized.
They're often produced, too, by hens who are old enough to
produce Extra Large eggs. Genetics is a factor, also. Occasionally
a hen will produce double-yolked eggs throughout her egg-laying
career. It is rare, but not unusual, for a young hen to produce
an egg with no yolk at all.
In ferlilized eggs, the yolk is the site of embryo formation.
It is the yolk which is responsible for the egg's emulsifying
properties.
How recently an egg was laid has a bearing on its freshness
but is only one of many factors. The temperature at which
it is held, the humidity and the handling all play their part.
These variables are so important that an egg one week old,
held under ideal conditions, can be fresher than an egg left
at room temperature for one day. The ideal conditions are
temperatures that don't go above 40∞F. (4∞C.)
and a relative humidity of 70 to 80 percent.
Proper handling means prompt gathering, washing and oiling
of the eggs with a few hours after laying. Most commercially
produced eggs reach supermarkets with a few days of leaving
the laying house. If the market and the buyer handle them
properly, they will still be fresh when they reach the table.
It is not true that freshness can be judged by placing an
egg in salt water. A carefully controlled brine test is sometimes
used to judge shell thickness of eggs for hatching purposes
but has no application to freshness of table eggs.
How important is "freshness?" As an egg ages, the
white becomes thinner and the yolk becomes flatter. These
changes do not have any great effect on the nutritional quality
of the egg or its functional cooking properties in recipes.
Appearance may be affected, though. When poached or fried,
the fresher the egg, the more it will hold its shape rather
than spread out in the pan. On the other hand, if you hard
cook eggs that are at least a week old, you'll find them easier
to peel after cooking and cooling than fresher eggs.
Classification determined by interior and exterior quality
and designated by letters - AA, A and B. In many egg packing
plants, the USDA provides a grading service for shell eggs.
Its official grade shield certifies that the eggs have been
graded under federal supervision according to USDA standards
and regulations. The grading service is not mandatory. Other
eggs are packed under state regulations which must meet or
exceed federal standards.
In the grading process, eggs are examined for both interior
and exterior quality and are sorted according to weight (size).
Grade quality and size are not related to one another. In
descending order of quality, grades are AA, A and B.
There is no difference in nutritive value between the different
grades.
Because production and marketing methods have become very
efficient, eggs move so rapidly from laying house to market
that you will find very little difference in quality between
Grades AA and A. Although grade B eggs are just as wholesome
to eat, they rate lower in appearance when broken out. Almost
no Grade B's find their way to the retail supermarket. Some
go to institutional egg users such as bakeries or foodservice
operations, but most go to egg breakers for use in egg products.
Grade AA
A 'Grade AA' egg will stand up tall. The yolk is firm and
the area covered by the white is small. There is a large proportion
of thick white to thin white.
Grade A
A 'Grade A' egg covers a relatively small area. The yolk is
round and upstanding. The thick white is large in proportion
to the thin white and stands fairly well around the yolk.
Eggs from hens fed rations having ingredients that were grown
without pesticides, fungicides, herbicides or commercial fertilizers.
No commercial laying hen rations ever contain hormones. Due
to higher production costs and lower volume per farm, organic
eggs are more expensive than eggs from hens fed conventional
feed. The nutrient content of eggs is not affected by whether
or not the ration is organic.
Several factors influence the size of an egg. The major factor
is the age of the hen. As the hen ages, her eggs increase
in size.
The breed of hen from which the egg comes is a second factor.
Weight of the bird is another. Pullets significantly underweight
at sexual maturity will produce small eggs.
Environmental factors that lower egg weights are heat, stress,
overcrowding and poor nutrition.
All of these variables are of great importance to the egg
producer. Even a slight shift in egg weight influences size
classification and size is one of the factors considered when
eggs are priced. Careful flock management benefits both the
hens and the producer.
Egg sizes are Jumbo, Extra Large, Large, Medium, Small and
Peewee. Medium, Large and Extra Large are the sizes most commonly
available.
Sizes are classified according to minimum net weight expressed
in ounces per dozen.
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