Eggs
The most popular and widely used eggs
are of hens in India, although eggs of turkeys, guinea fowls, and ducks are
also used. The colour of egg shells and egg yolks varies with the breed of hen
and the food they eat; but this makes no difference to the food value. They are
rich in proteins and contain valuable amounts of iron and vitamin A&B. The
ideal storage temperature for eggs is 2-5 degree C.
Food value:
Eggs have been described as a “complete food”. One egg is equal to
seventy calories of energy and contains carbohydrates, fats, proteins, mineral
salts, vitamins and water.
Vitamins A, B, D, are all necessary for health and growth; iron,
phosphorus and calcium are essential for building and maintaining healthy
bodies. The average of egg shell, yolk and egg white in an egg is : 10%, 30%
and 60%. Water constituency in egg is about 73%.
Structure of an egg:
Shell:
It is the outer covering of the egg and is composed of calcium
carbonate. It may be white or brown depending upon the breed of the chicken.
The colour of the shell does not affect cooking quality, character or
nutrition.
Yolk:
This is the yellow portion of an egg. Colour of yolk varies with the
feed of the hen, but does not indicate the nutritional content.
Vitelline:
It is a clear seal that holds or surrounds the egg yolk.
Chalazae:
These are the twisted cordlike strands of the egg white. They anchor the
yolk in the centre of the egg. Prominent chalazae indicate high quality.
Shell membranes:
Two shell membranes, inner and outer membrane, surround the albumen.
They form a protective barrier against bacteria.
Air cell:
It is the pocket of air formed at the large end of the egg. Air cell
forms between the membranes. This is caused by the contraction of the content
on cooling after egg is laid. The air cell increases with the age of the egg as
there is considerable amount of moisture loss.
Thin albumen:
It is nearest to the shell. When the egg is broken there will be a clear
demarcation of the thin and thick albumen. As the egg gets older these two
albumens tend to mix into one another. This is again a test of good and fresh
egg.
Thick albumen:
It stands high and spreads less than the thin white in a high quality
egg. It is an excellent source of riboflavin and protein.
Classification:
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Basis of classification
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Source(bird)
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Farm & feed
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Grade
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Sizes
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US
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weight
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European
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Weight
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Hen
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Battery farm
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AA
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Jumbo
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73
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Extra large
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73
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Duck
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Barn laid
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A
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Extra large
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63
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Large
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63
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Types
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Turkey
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Free range
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B
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Large
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53
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Medium
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53
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Goose
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Organic
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C
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Medium
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45
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Small
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45
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Pigeon
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Vegetarian
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Small
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40
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Quail
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Omega-3
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Peewee
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35
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Guinea fowl
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Vitamin enhanced
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Source of egg:
Eggs are named after the birds that laid the eggs. Eggs can be
distinguished by size and colour of the shell. Various birds are like hen,
turkey, duck etc.
Farm and feed:
Eggs are named after the farming method employed or the feed provided to
the bird to enhance a particular nutrient in the egg.
Grade:
Eggs are named after the quality grades awarded to them based upon set
quality factors/parameters.
Sizes:
Eggs are named after their sizes, which are assigned to them based upon
their weights. The sizing is based upon per dozen of eggs, but is represented
as weight of individual egg after taking out mean weight per egg for ease.
Selection of eggs:
Physical appearance:
When purchasing eggs one should observe the physical appearance of eggs;
no cracks, no dirt, colour and size.
By looking/finding for a “bloom”, that gives it a feeling much like that
of a thin lime coating.
Candling:
This method of determining the freshness of eggs consists of placing a
piece of cardboard containing a hole, a little smaller than an egg between the
eye and a light, which may be from candle or electric light and holding the egg
in front of the light. The rays passing through the egg show the condition of
the egg, the size of its air cell, the growth of mould, or spoiling of the egg
by any ordinary means.
Shaking:
One can determine the freshness of an egg by shaking it. When the water
inside the shell evaporates, the yolk and white shrink so much that they can be
felt moving from side to side when the egg is shaken. Staler the egg, more
pronounced the movement becomes.
Floating:
A test for freshness which consists in placing the eggs in glass
containing water will be found effective. A perfectly fresh egg will sink when
it is put into the water, but if the egg is three weeks old the broad end will
rise slightly from the bottom of the glass. An egg that is three months old
will sink into the water until only a slight portion of the shell remains
exposed; whereas, if the egg is older or stale, it will rise in the water until
nearly half of it is exposed.
Storage of eggs:
Ø Eggs should be used
within a month and stored unwashed, with the pointed end down, in the cold part
of the refrigerator.
Ø Washing the egg
makes the shell permeable to smells, so strong smelling foods, such as cheese,
onion, garlic and ginger, should not be stored near the eggs.
Ø A hardboiled egg
will keep for four days if unshelled and two days if shelled.
Ø Once broken, egg
yolk will keep for 24hrs. And egg white for 6to12 hrs, in a refrigerator.
Ø Wider end of egg
should be kept up, while storing.
Ø Average temperature
for storage is 2-5degree C.
Uses of eggs :
v Binding: addition of eggs to
minced meat and mashed vegetables etc. helps to bind the mixture. As heat
coagulates, the proteins are bound into a cohesive mass.
v Coating: the egg and egg
batter help to give a coat to the food items and prevent them from
disintegrating and give them a protective coating.
v Leavening: by beating the egg
whites, foam is made up of air bubbles, surrounded by a thin elastic film of
egg white. This mixture, when added to products such as sponge cake, meringues,
etc. increases the volume and the egg white film hardens.
v Emulsifying: eggs form stable
emulsions. eggs are used as an emulsifier in mayonnaise, ice creams, cakes etc.
v Thickening: eggs help to
improve the consistency of gravies, curries, sauces and soups. Egg liaison used
in soups and sauces help to thicken and improve consistency.
v Decoration and
garnishing of dishes: slices, sieved, or quarters of boiled
eggs are used to garnish dishes such as salad, biryanis, curries etc.
v Clarifying: consommés are
clarified with egg white.
v Taste, flavour,
shine: enhances colour and sheen, enrich and enhance the flavour and taste. Egg
wash gives a shiny appearance.