Egg lecture

1- Egg nutritive value
2- Egg processing
3- Egg preservation
4- Egg functional properties
5- Egg faults
Notes on
Egg hygiene
4/18/2020 1Dr.Dina A.B. Awad

Changes occurs in egg after laying
1- Changes in pH or the alkalinity of egg.
2-Increase of gas contents.
3- Changes in viscosity of egg albumin.
4- The evaporation content of egg albumin.
5- Flavor of egg and the smell changed….leads to egg rot.
Factors to produce high quality egg
1- Select a good bird breed with good genetic characters.
2- Providing a clean farm .
3- Feeding the poultry a well balanced diet.
4- Frequent collection of egg after laying.
5- Proper egg handling.
6- Egg storage under low temperature and low humidity.
7- Good oil preservation for storage.
8- Washing the dirty egg before oiling.

Egg nutritive value 1- Contain all essential nutrients needed for growth.
2- It rich with a high quality protein.
3- It is contain iron and trace element.
4- Good source of essential fatty acids and vitamins.
Eggs are: 10% shell, 60% white, 30% yolk
10% shell
60%
white
10% protein
90% water
16% protein
32% fat
50% water
30%
yolk
They are good sources of protein,
calcium, iron and B vitamins
Two eggs provide:
20% of your daily protein needs
8% of your daily iron needs
8% of your daily calcium needs
Two eggs also provide 15% of the daily fat you should eat
This fat is a saturated fat - an animal fat
4/18/2020 Dr.Dina A.B. Awad

It is ideal method, most egg are cleaned
By washing using a special sanitizer. Rinsing
By wormer water and finally drying.
Egg washing
Spraying method Brushing method
The egg rotating during washing using
pressure spray. The most common chemical
Used is chlorine compound 50ppm.
Egg antimicrobial defense
1- Intrinsic factors .2- Extrinsic factors .
1- Egg cuticle.
2- Shell membranes.
3- Egg albumen.
4- Vitelline membrane.
1- Bactericidal effect of egg proteins.

Egg processing (products)
Frozen egg : (frozen whole egg, frozen yolk, frozen white) put in cans at -18-26ºC/8 min.
to avoid gummy mass appearance of yolk add 5% sugar or 10% glycerin.
Dried egg : Drying using spray method like milk powder. In which water % not more
than 5%.
Liquid egg product: whole liquid egg, liquid egg white and liquid egg yolk.

Egg breaking and separation

Egg Product Refrigerator Freezer
Raw eggs in shell 3 to 5 weeks Do not freeze. Instead,
beat yolks and whites
together; then freeze.
Raw egg whites 2 to 4 days 12 months
Raw egg yolks 2 to 4 days Yolks do not freeze well
Egg Storage
(Foodsafety.gov.uk)

8
Types of egg defect
1- External defect (shell defect).
2- Internal defect (white defect , yolk
defect and air cell defect).

9
gross cracks egg (leakers)
Def: it is large cracks and holes that
result in broken in shell membranes
incidence: increase with age (1-5)%of
total production
Causes 1-aging 2-poor nutrition
3-saline water 4-disease
5- High. Temp. 6-mecanical
damage 7- rough handling
Def: very fine cracks run along the
shell difficult to be detected by
naked eye need candling
Incidence: (1-3)% of total
production
Hair line cracks Star cracks
Def: fine cracks radiating out
wards from a central point of
impact .Incidence: (1-2)%of
total production
N.B: Cracks can be detected by candling only in which shell
membranes are sound Like hair line cracks and star cracks

10
Fly marks
Def: Means marks caused by
flies leaving droppings on egg
shell
Cause: when egg exposed
to large No. of flies
(unhygienic conditions)
Control: Avoid flies
pimpled egg
Def :Pimples means small lumps of
calcified material on egg shell
Cause :Thought to be caused by
foreign material in oviduct which ass
.with
1-aging 2-poor nutrition 3-strain of
bird
Shell less egg
Egg with very thin shell or no
shell around the shell
membranes it is highly
susceptible to damage (0.5-6)%
more common in bullets (female
bird come to lay in her first
season
cause: 1-immature shell gland
2-defect in shell gland
3-poor nutrition
4-saline water 5-disease

11
Flat sided egg
When part of shell is
flattened and the adjoin
part of shell is wrinkled
.due to stress
crowding In correct
change in lightening
Cage marks
Its refers to dirty or translucent
marks or lines present on shell in well
managed flock occur less than
5%due to rusty or dirty wires in cage
floor But the translucent marks due
to high humidity or crowding
very small holes in egg shell
- less than 0.5%
- caused by faulty in laying
(aging ,poor nutrition ,small
sharp projection
Pin holes shell

12
Fungus or mildew on
shell (mold growth).
Shell affected by green or
black powdery like material
Cause : poor hygiene during
handling ,storage,
transportation Or worm
storage room orold age
Mottled or glassy
shells
Parts of egg appears
transparent so appears
mottling or glassy such
shell are easily broken
shell appears under
candling
Sandpaper or
rough shell
Shell with rough texture
areas with un even
distribution over the shell
This case less than 1%but
increase with early
production in case of
double ovulation one is
shell less and other is extra
shell production
Stained eggs
• All or parts of shell are
stained by various
material like blood or
faces Blood stains is the
most common at bullets
due to first time of laying
Cause by blood from
prolapesed cloacae ,fecal
contamination ,water
stains, sanitizers ,oil stains
,drugs due to
chlortetracycline

13
2- Internal defect (white defect , yolk defect and air cell defect).
Blood spot
Differ from few to large
amount on yolk surface acc.
To bird strain (10%) this due
to rupture of blood vessels in
ovary or oviduct that in case
of 1- level of vit. A in diet
2-vit K antagonist
3-fungal toxin 4- stress
5-avian encephalomyelitis
6-bird strain .
Bloody egg
blood not
concentrated but
diffused through
white or around yolk
Pieces of tissue from body
organs usually brown in
color usually in thick
albumin or chalazae or yolk
from 0.5 to 3mm in
diameter - ranges from 3 to
30% acc. To strain ,age may
higher in brown egg
Meat spots Heat spots
Strong fertile egg at
20 c so fertile germ
cell will be enlarged
has dark color than
normal egg yolk color

14
Spread yolk
Yolk content spread within white and yolk has abnormal shape and irregular shape.
The yolk displaced to another place other than from its central position
Sided yolk
yolk is stucked to the inner shell membrane .this condition favors rabid growth of mold or bacterial at area of contact
Stucked yolk
Pale yolk
Normal egg yolk color is from deep yellow to orange yellow due to substance called carotenoids .
But the nutritional value of the yolk not affected .due to, insufficient carotenoides in feed
Rotten egg
Bacterial or fungal contamination can produce red or green rots looks smells putrid such egg should be eliminated
from egg Caused by fecal contamination or improper washing procedure
Discolored white
White changed than normal slightly changed to yellow green color or may be become pink coloration .this caused by :-
1-feeding diet contain more than 5%cotton seed oil as contain cyclopropanoid F.A. cause white to be pink .
2-poor storage and very old egg.
incubated egg
Tainted egg : egg with abnormal odour
presence of halo around the germ cell this means incubation of fertile egg

15
Round worms in egg
Some eggs contain one or more round worms
intestinal parasite
caused by :-
1-migration of parasite from cloacae to oviduct
then enclosed during egg formation
Watery albumin
Watery albumin due to long storage as it
become watery and transparent Causes of
change in color from cloudy appearance to
transparent??
Reject extremely dirty eggs .
the broad end upper most and hold
against the aperature of the candling
lamb and twisted along its longitudinal
axis
Grade AA
Normal arrangement of
egg in racks4/18/2020 Dr.Dina A.B. Awad

16
Air cell defect
1-large air cell more than 7mm
2-running air cell
part of inner shell membranes is broken so air bubbles will be found in white This occurs when
packed wrongly
3-ringed air cell
Very large air cell sharply defined with grey or brown colored edges

• bloody egg
• Incubated egg
• Rot egg
• Stuck yolk
• Spread yolk
• Mold growth
• Discolored white and yolk
• Tainted egg
• Meat spot
• Large air cell
• Dirty shell
• Ringed air cell
• Small blood spot
• Sided or patchy yolk
17
Unfit for human Immediate use (for sale rabidly)
Judgment of egg

Egg Preservation
Aim : 1- to prevent the penetration of microorganisms.
2- prevent the multiplication of microorganisms.
3- prevent evaporation of moisture content.
Small scale Large scale
1- Glass water method: using Na silicate
2- Lime water method
3- Bran method
1- Gold storage at 4ºC ,RH 75-85%
2- Sterilization : By O3
3- Oil dipping: Parafin oil.

Egg preservationIn considering the
preservation of the egg quality,
it is assumed that the chicken
egg is at its highest quality at
the time of laying. Anything
done to the egg later results in
quality loss. It is important
that the egg shell must be
clean, smooth and intact
before preservation. All
preservation methods for shell
eggs have been designed to
retard one or more of the
physic-chemical alterations
which lowers the egg quality
as it ages.

1. Egg cleaning followed by oiling:
All stained or dirty shells can be cleaned in two methods
The simplest dry cleaners are hand abrasive blocks to scratch the dirt or stain from the
shell surface. Disadvantage of dry cleaning is weakness of the shell. Only dirty and
unsound eggs should be cleaned.
A)dry cleaning
B) wet cleaning
Egg wash water temperature need to be at least 11ºC higher than egg
temperature. The temperature differential between the eggs and wash water
also critical, as a difference of more than 10ºC results in increased number of
thermal cracks due to expansion of contents of egg. The water temperature of at
least of 35ºC (95°F) is needed for adequate cleaning. Recycling water shouldn't
used for cleaning.
Oiling after cleaning
Oil coating preserves the egg by forming a thin film on the surface of the shell and
thereby sealing the pores. Washing and subsequent coating preserve eggs much
better than coating alone. The oil used must be odourless, colourless and free from
fluorescent materials. Mineral oils of food grade are less susceptible to oxidative
changes during storage. Eggs can either dipped in oil or sprayed with it.

B) wet cleaningA)dry cleaning

For start period storage, fresh eggs should be 12.5-15.5ºC and 70 - 80%
relative humidity. For long term storage the room temperature should
be at -10ºC (14±1°F) and relative humidity 80- 90%, as this relative
humidity will sufficiently retard evaporation without danger of mould
growth. Eggs can be oil treated prior to cold storage to enhance their
keeping quality. The quality of the shell eggs can be maintained for 6
months in a cold storage.
2. Cold storage

liquids like lime water and water glass are very use full. This is old
method of preserving the quality of shell eggs especially for home use.
Eggs are dried at room temperature and transferred to filler flats. The
eggs can be stored for 3 to 4 weeks at room temperature. The
preservative effect of the lime water is partially due to its alkalinity. It
deposits a thin film of calcium carbonate on the egg shell and partially
seal the pores. The water glass is sodium silicate after immersion over
night in water glass. It deposits a thin precipitate of silica on the
surface of egg shell, possesses intrinsic antiseptic properties and dose
not impart odour or taste to the eggs. The water glass preserved eggs
and stored at 13 to 15ºC for six months.
4. Immersion in liquids
This involved for immersion in hot water or oil for sufficient time to
to stabilize the thick albumen. The immersion in water and oil at
600C(1400F) for 14 minutes.
3. Thermostebilization

The eggs can be preserved by pickling also. It can be done with eggs of small
size like that of quail eggs as it will allow proper penetration of pickling solution
throughout the egg.
5. Pickling

Egg functional properties
*Adhesion
The proteins in egg products, specifically in the whites, assist with adhesion and ingredient
binding. When they are heated or exposed to acid, they coagulate, causing the egg product to
change from a liquid to a semisolid or sold. When the proteins solidify, they function as an
adhesive, connecting ingredients or food components with each other.
*Browning/Color
The proteins within eggs c“We eat with our eyes first,” says one article on baking,1 with color so
important for baking success that companies actually make meters to measure it. Egg products
can contribute to product color in two ways; browning on the product exterior in the case of
baked goods, or the product itself such as coloring mayonnaise or muffin interiors.
an participate in the Maillard reaction when exposed to heat, producing a desirable brown color.
The Maillard reaction is responsible for the golden crust of baked products such as yellow batter
cake,2 meat browning and the dark color of roasted coffee.
*Flavor
Egg contributes in enhancing food products and bakeries. Taste or flavor is the deciding factor
for consumers who purchase foods and beverages

Egg albumen has excellent food foaming proper-ties. Such properties are determined
by the ability to rapidly adsorb on the air-liquid interface during whipping or bubbling,
and by its ability to form a cohesive viscoelastic film by way of intermolecular
interactions
1- Egg foaming properties
Protein molecules act as hydrophilic and hydrophobic groups. The hy-drophilic groups
are arranged towards the water phase and the hydrophobic groups towards the air
phase. During the whipping process air comes into the solution to form bubbles, the
hydrophobic regions facilitate the adsorption at the interface,process that is followed
by partial unfolding (sur-face denaturation).

2- Egg emulsification properties
Egg yolk is composed of a large amount of surface active components, such as
different protein species and phospholipids. These surface active components can
form an interfacial film between an oil phase and a water phase and thereby stabilize
an emulsion. Egg yolk is therefore used in many food emulsions, such as mayonnaise
and dressings.
Oil
Proteins, phospholipids,
lipoproteins
Water
3 Components necessary for emulsion
a) oil
b) water
c) interface, proteins, phospholipids, lipoproteins

Hen egg white have been extensively used as processed food ingredients, because of
their functional properties of gelation,
Gel is an intermediary form between solid and liquid. It is the cross-linking among
polymeric molecules which make an intermolecular network within a liquid medium.
3- Egg gelation properties

1. Avoid excessive temperatures
2. Avoid excessive cooking time

Cooking Methods – whole eggs
Boiled
For perfect cooking, start with eggs
that don't have any visible cracks
To get perfectly peeled hard-cooked
eggs, use eggs that are at least 3 to 5
days.
Bring your eggs to room temperature
before cooking.
Gently place the eggs in a single layer
in a pan with enough cold water to
cover eggs completely (approximately
by 1 inch).
As soon as the water reaches a rapid
boil, remove pan from heat and cover
egg pan tightly with a lid.
For Large Egg
Soft-cooked yolk 4 to 5 minutes
Medium-cooked yolk 6 minutes
Hard-cooked yolk 17 minutes

Carton Labeling

Egg structure

Which is the highest quality egg?

Duck Hen Ostrich GooseQuail
Different egg
breeds
34

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

Egg lecture

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