Egg hygiene

-Structure and composition of egg
Early stage fertile egg Late stage Fertile egg
Egg composed of a yolk at the centre, surrounded by albumen (egg
white), both of which are enclosed within the shell.
24/14/2020 Dr.Dina A.B.Awad

The eggshell
The shell is built of 8-10,000 pores, which ensures
that oxygen can penetrate and CO2 and other gases
can escape. The shell represents about 10 % of the
weight of the egg and consists mainly of calcium
carbonate and calcium phosphate. The shell
thickness and thus the strength depends on egg size,
breed, the age of the hen, and feed composition.
Consider as egg barrier.
Only the outer layer of the shell is coloured. The colour
of the shell can be white or brown – depending on the
breed.(ooporphyrin brown pigment).
Cuticle, bloom, shine
As egg shell contains many pores that consider a gateway for microbial entrance so, nature
provided the shell with a protective layer formed from proteins covered these pores but
unfortunately this layer easily removed by rough handling and washing. A colourless wax
membrane called the cuticle surrounds the outer shell. It is highly alkaline and therefore acts
bacteriostatic. (indicator freshness)
Shell pores It most present at broad end than
narrow end or sharp end

Shell membranes
Under the shell there is an outer and an inner shell membrane. The outer membrane, which is
immediately inside the shell, is the most resistant. Besides serving a a barrier role, the shell and
the shell membranes have a biological function; namely to regulate evaporation and air
circulation, but also to prevent penetration of microorganisms. It has a network of fibers
interlacing against each other ,has a bactericidal effect Consider as egg barrier
When the egg leaves the hen, it has a temperature of 41 °C.
When it is cooled, there is a contraction of the contents and air
can penetrate through the shell. In the broad end of the egg,
the outer and the inner shell membrane are split forming an
empty space called air cell is formed here. The older an egg is,
the larger the air cell, as water continuously evaporates from
the egg during storage. It is less than 3mm in newly fresh egg y
the time of storage it enlarged (indicator freshness)
Air cell
pores
pores
As the egg ages, moisture and carbon dioxide leave through the
pores of the shell, air enters to replace them and the air cell
becomes larger.

The egg white
The egg white represents approx. 60 % of the weight of the egg and consists of 88 % water and
12 % dry matter, primarily protein.
The white is divided into four alternating layers contain approximately 40 different proteins,
Although to the naked eye albumen appears homogenous, it actually is fibrous and
multilayered. :
1- outer thin layer 2- inner thick layer
3- outer thin layer 4-inner chalzerfious layer
The pale yellow-colour of the white is due to the presence of riboflavin (vitamin B2). In
completely fresh eggs there are lots of small air bubbles, which can give the egg white a dull
clody appearance. This is because of carbon dioxide that has not yet leaked out through the
shell. The older the egg, the more transparent the egg white. The white provides cushioning and
additional nutrition for the developing chick and contains less nutrition than the yolk. The
cloudy appearance comes from carbon dioxide. As the egg ages, carbon dioxide escapes, so the
albumen of older eggs is more transparent than that of fresher eggs.
CHALAZAE Opaque ropes strands of egg white, the chalazae hold the yolk in the center of
the egg. Like little anchors, they attach the yolk’s casing to the membrane lining
the eggshell. The more prominent the chalazae, the fresher the egg (indicator
freshness)
The albumen has several functions, a bactericide to prevent infection and as a template for
the deposition of the shell membranes. The white prevents external bacteria from
penetrating the yolk.

The yolk has a much lower water content than the egg white, just under 50 %. consists of approx.
2/3 fat and 1/3 protein. The fat content consists primarily of triglycerides, cholesterol, and the
phospholipid lecithin. The amount of fat and cholesterol and the composition of the fat is
influenced by the diet of the hen.
The diet of the hen determines the colour of the egg yolk. If the hen is mainly fed by yellow and
orange-pigmented food, this is the colour that is more prominent in the egg yolk. A relatively
colourless feed, gives almost colourless yolks. It is the main source of nutrient for the emryo.
Yolk rich in vit A, carotene ,vit B1,B2 and rich with phospholipid.
The egg yolk
golden or lemon-
coloured
Vitelline Membrane The clear casing that encloses the yolk. Its strength protects the yolk
from breaking(prevent its leakage). The vitelline membrane is
weakest at the germinal disc and tends to become more fragile as the
egg ages. (indicator freshness)
a slight depression on the surface of the yolk. When The egg
is fertilized, sperm enter by way of the germinal disc, travel
to the center and a chick embryo starts to form.
Germinal Disc

Physiology of Egg production
Events that occur with increasing photoperiod:
• Hypothalamus responds to increasing photoperiod
• Hypothalamus signals anterior pituitary to produce FSH
• FSH = follicle stimulating hormone
• FSH travels to ovary in blood
• Stimulates development of follicles
Hypothalamus
Anterior pituitary
Ovary
FSH
Follicle maturation

Egg structure

The formation of an egg occurs in the ovary and oviduct. The
largest follicle is the one to be ovulated to produce an egg. The
follicular membrane ruptures and releases the follicle at the time
of ovulation. This usually occurs about 30 minutes after the hen
has laid an egg.
After ovulation, the yolk is captured by the infundibulum. The
formation of the chalazae and perivitelline membrane occurs in
this section of the oviduct.
It will take approximately 15 minutes for the yolk to pass through
the infundibulum. Fertilization occurs in this region of the oviduct
in breeding birds
The hen’s reproductive system is a very complex system (only left
ovary is active) that can produce an egg in 24 hours from
ovulation to oviposition. An egg consists of the yolk (30 – 33%),
albumen (~ 60%), and shell (9 – 12%).
-Physiology of egg composition

-Physiology of egg composition
The magnum is the longest part of the oviduct and
the yolk will take 2-3 hours to pass through the
magnum.
Next, the developing egg passes into the isthmus,
where the inner and outer shell membranes are
formed. This process takes approximately 1½ hours.
The egg then enters the shell gland or uterus,
where it will spend 18 to 21 hours. During that time
the albumen takes up electrolytes and water
through a process called “plumping”. The shell,
which consists of roughly 95% calcium carbonate
and 5% organic material, is also formed
in the shell gland.
Once the shell is completely formed, a protective
coating called the cuticle is laid down over the shell.
The laying of the egg, or oviposition, is induced by
hormonal contractions of the uterus.
The egg passes through the vagina and exits via the
cloaca. 10

Chemical Composition of Egg White
• Mostly Water
• Approximately 10-12% protein
• Contains only a trace of fat
• A good source of riboflavin
• Contains most of the protein, niacin, riboflavin, choline, magnesium, potassium,
sodium and sulfur found in an egg
• Contains trace amount of carbohydrates
Chemical Composition of Egg yolk
• Approximately 50% water, 17% protein and 33% lipids
• Minerals: iron, phosphorus, calcium, manganese,
iodine, copper, and zinc
• Vitamins A and D, B12, E, biotin, choline, folic acid,
pantothenic acid, pyridoxine and thiamin
• Xanthophylls: main yellow pigment
Water
Protein
Lipids
50%
33%
17%
% Water Protein Fat Ash
Whole 100 65.6 11.8 11.00 11.7
White 58 88.0 11.0 0.2 0.8
Yolk 31 48.0 17.5 32.5 2.0

Ovalbumin 54%
Ovotransferrin12%
Ovomucoid 11%
Ovoglobulin 4%
Ovomucin 3.5%
Lysozyme 3.4%
Ovoinhibitor 1.5%
Ovoglycoprotein 1%
Flavoprotein 0.8%
Ovomacroglobulin 0.5%
Avidin 0.05%
Cystatin 0.05%
12

Proteins of Egg White
13

Eggs May Be Used To . . .
Thicken ----- Sauces, Puddings, Cream Fillings, Soft and Baked Custards
Leavening ------ Sponge Cakes, Butter Cakes
Binding ------- Meat Fish and Egg Loaves, Vegetable Casseroles
Emulsifying ----- egg yolk is a natural emulsifier - it stops water and fat separating. When an
egg yolk is combined with oil and vinegar it makes a stable mixture: mayonnaise
Crystallization ----- Ice Cream
Foaming------ egg white can increase in volume by as much as 8 times when beaten - air bubbles
are trapped by the protein
Glazing &Coating ------ shiny brown finish can be achieved on bread, pastry or biscuits
Breaded Meats, Breads, Rolls, Cakes and Cookies
Eggs Add Flavor and Color: Eggs contain fats which carry flavors in food products

Step 1: Laying
Step 2: Collecting
Step 3: Washing
Step 5: Candling and Grading
Step 6: Sizing
Step 4: Oiling
Step 7: Packing
Step 8: Cooling
Step 9 : Shipping,
Step 10: Selling
10 Steps on the Journey From Hen to Home
154/14/2020

16
Grade AA Grade A Grade B/C
Egg Quality & grading
Egg will stand up tall (tomed
shape). The yolk is firm and the
area covered by the white is small.
There is a large proportion of thick
white to thin white.
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
egg.
Eggs spreads out more. The
yolk is flattened and there is
about as much (or more) thin
white as thick white.

17
Egg Size
Jumbo Extra
Large Large Medium Small Pee
Wee
peewee,
small,
medium,
large, extra
large, and
jumbo.
peewee
20-30g

Egg Safety
• Salmonella Enteritidis (SE) has been found inside a very small number of eggs. SE will not grow at
temperatures below 40˚F and is destroyed when heated to 160˚F during thorough cooking, or in
acid media with a pH lower than 4.0. Pasteurization was federally mandated in 1966 to protect
against Salmonella organisms, at highest possible safe temperatures:
The approved methods using to pasteurize Whole Eggs 56.7°C for 3.5minutes or 55.6°C for 6.2
minutes.
Heating above 57°C will damage egg white and increase whipping time,. Whipping agents, such as
triethylcitrate and sodium lauryl sulfate, may help restore some foaming properties of heat-
damaged egg white..
Basic Principle of Egg Cooking
Use a moderate to low temperature with exact
timing. WHY: When eggs are cooked at too
high a temperature or for too long at a low
temperature, egg whites shrink and become
tough or rubbery - - yolks toughen and their
surface may turn gray-green????.
18

1- Individual candling
2- U.V lamb
3- On large scale2- On medium scale
1-Mass candling1- Floating Test
2-Brine test
3-Breaking test
4-Shaking test
1- On small scale
1- Floating Test
Test of egg freshness
Egg immersed in tape
Water the fresh egg
will sink and the old
one will float
2- Brine Test
Egg immersed in brine
sol the fresh egg will
sink and the old one
will float.
Sink horizontally
Sink horizontally and broad
end slightly upwardSink vertically
Float at different levels

3- Breaking Test
Yolk is round ,consized,
Tomed shape,thick albumin
is consized and prominant
Yolk is round ,consized,
thick albumin is slightly
consized and slightly
prominant
Yolk is flattened ,
Thin Albumen spread in
the pan and watery
20
4- Shaking Test -Fresh egg ----no sound Old egg-------- emit sound ??????

1- individual candling
by using candling lamb 60 watt
which performed in dark room
2- U.V lamb
One day old 7day old 2-3 week day old
21
Method: Hold small end of egg with thumb, index, and middle fingers Put large end of
egg against candler at a 45 degree angle Carefully rotate egg Look for blood / meat spots
Check size of air cell, yolk shadow
On medium scale

On large scale
Mass candling : it depend using quartz lamb --- the fresh egg will show
Violet or red pink color where the old one will show blue color .

Thank you for attention
Presented by :
Dr. Dina A. B. Awad
Lecturer of food hygiene department
Faculty of veterinary medicine
Benha university , Egypt
4/14/2020 23Dr.Dina A.B.Awad

Egg hygiene

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