Egg quality defects Grading of eggs Microbiology of eggs Sources of contamination Antimicrobial defense of egg Diseases transmitted through egg Prevention of spread of diseases through eggs

1. Dr. Zeinab I. Ali , M.V.Sc., PhD.
Department of Food Hygiene and Control
Faculty of Veterinary Medicine, CU
Email: Zeinab_ali@cu.edu.eg
EGG QUALITY DEFECTS

2. AGENDA
• Egg quality defects
• Grading of eggs
• Microbiology of eggs
• Sources of contamination
• Antimicrobial defense of egg
• Diseases transmitted through egg
• Prevention of spread of diseases through eggs
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3. EGG QUALITY DEFECTS
• food quality can be defined as the sum of characteristics
of a given food item which influence the acceptability or
preference for that food by the consumer. Based on this
definition, Egg Quality Defects is compounded of these
characteristics of an egg that affect its acceptability to
the consumer.
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4. EGG QUALITY DEFECTS
• the Animal Products Specification for Products Intended
for Human Consumption Notice 2000 requires that shell
eggs intended to be traded in the shell must:
• Be visibly clean
• Have no cracks that are visible on candling
• Have no evidence of embryo development or putrefaction,
and no significant blood clots
• Not have been incubated
• Be handled and stored under conditions that minimise
condensation on the surface of the eggs
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5. EGG QUALITY DEFECTS
• Problems associated with egg quality include: egg shell
defect and internal defects which can be broadly
categorized into three groups namely: defects affecting
yolk quality, defects affecting albumin quality and
defects affecting overall quality.
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6. SHELL QUALITY DEFECTS
1. Misshaped Eggs
2. Sandpaper or Rough Shelled Eggs
3. Soft, Weak or Shell less Eggs
4. Dirty and Glazed Shells or Stained Eggs
5. Body Checks
6. Cracked Eggs
. Gross Cracks
. Hairline Cracks
. Star Cracks
7. Flat-sided Eggs
8. Pimples
9. Pinholes
10. Mottled or Glassy Shells
11. Fungus or Mildew on Shells
12. Cage Marks Shells
13. Fly Marks Shells
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7. (A). SHELL QUALITY DEFECTS:
1- Faulty shell: rough or misshaped.
Misshaped
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8. (A). SHELL QUALITY DEFECTS:
2-Dirty shell: Dirt, blood and/or fecal matter.
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9. (A). SHELL QUALITY DEFECTS:
3-Cracked shell: The egg shell is broken, while the
shell membranes are intact.
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10. (A). SHELL QUALITY DEFECTS:
4- Leaker shell: The egg shell is broken, and the shell
membranes also, the contents escape outside.
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11. (A). SHELL QUALITY DEFECTS:
5-Soft or weak shell or shell less Eggs
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12. (A). SHELL QUALITY DEFECTS:
6- body checks:
Shell are marked by grooves and ridges (checks).
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13. (A). SHELL QUALITY DEFECTS:
7- flat sided egg
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14. (A). SHELL QUALITY DEFECTS:
8- Pimples eggs
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15. (A). SHELL QUALITY DEFECTS:
9- Pinholes
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16. (A). SHELL QUALITY DEFECTS:
10- Mottled or Glassy Shells:
When parts of the egg shell are translucent, it appears
mottled or glassy. Such shells can also be thin and
fragile.
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17. (A). SHELL QUALITY DEFECTS:
11- Fungus or Mildew on Shells
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18. (A). SHELL QUALITY DEFECTS:
12-Fly Marks Shells
Caused by flies leaving drooping on the egg shell.
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19. (A). SHELL QUALITY DEFECTS:
13-Cage Marks Shells
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20. (B). AIR CELL DEFECTS:
1- Large air cell:
More than 7 mm.
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21. (B). AIR CELL DEFECTS:
2-Running air cell:
Air cell or bubbles are found between the two shell
membranes and usually is due to improper storage.
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22. (B). AIR CELL DEFECTS:
3- Ringed air cell:
In which air cell is very large and sharply defined with gray
or brown colored edges, usually due to microbial growth.
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23. (C). WHITE QUALITY DEFECTS:
1- Discolored Albumin:
In which albumen has a
gray, red, green or blue
color. The different colors
are due to different
spoilage microorganisms.
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24. (C). WHITE QUALITY DEFECTS:
2- Cloudy Albumen:
In which albumen appears turbid due to either bacterial rot
or washing egg with too hot water.
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25. (D). YOLK QUALITY DEFECTS:
1- Sided yolk:
Yolk is displaced from
its central position
(Faulty packaging).
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26. (D). YOLK QUALITY DEFECTS:
2- Stuck yolk:
Yolk is stuck to the inner
shell membranes
(Favors the microbial
growth)
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27. (D). YOLK QUALITY DEFECTS:
3- Flattened yolk:
water content of the egg migrates from the thick white to
the yolk through the vitelline membrane; the yolk becomes
enlarged and flattened.
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28. (D). YOLK QUALITY DEFECTS:
4- Spread yolk:
The yolk becomes enlarged and flattened, vitelline
membrane may rupture leading to spreading of the yolk
contents in the white.
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29. (D). YOLK QUALITY DEFECTS:
5- Mottled yolk:
Uneven distribution of water migrates from
white.
6- Heat spot:
Enlargement of the germinal disc due to
storage of fertile eggs at the temperature
over 20C.
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30. (E). GENERAL QUALITY DEFECTS:
1- Blood spots:
Blood spots or clots are found in the white or adhere to yolk
which lowers the grade of eggs. It is due to rupture of blood
capillaries in the yolk follicle during ovulation.
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31. (E). GENERAL QUALITY DEFECTS:
2- Blood egg:
Blood is diffused
through the white or
spread around the yolk.
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32. (E). GENERAL QUALITY DEFECTS:
3- Incubated egg:
Fertile egg has a halo
around the germinal
disc (Blasto-disc). In
advanced incubation,
will developed blood
vessels or even embryo
may found on the yolk.
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33. (E). GENERAL QUALITY DEFECTS:
4- Meat spots:
All foreign bodies within the egg, except blood is called
meat spots.
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34. (E). GENERAL QUALITY DEFECTS:
5- Rot and Mold growth:
Microbial contamination of the egg contents.
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35. (E). GENERAL QUALITY DEFECTS:
6- Tainted Egg:
Egg with any abnormal
odor.
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36. QUALITY DEFECTS THAT RENDER
EGGS FIT OR UNFIT HUMAN
CONSUMPTION
Defects or faults that render eggs unfit for
human consumption
Defects or faults that render eggs
suitable for rapid consumption
1- Bloody egg1- Blood spots
2- Incubated egg2- Large air cell
3- Stuck and Spread yolk3-Running air cell
4- Rotted egg4- Sided yolk
5- Mold growth5- Dirty egg
6- Cloudy white6- Mottled yolk
7- Discolored white7- Faulty shell
8- Leaking shell
9- Meat spots
10- Tainted eggs (abnormal odor)
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37. GRADING OF EGGS
Egg grading involves inspection of the shell for
soundness, cleanliness, apparent strength and shape,
checking the interior of the egg by candling and sorting
into sizes on the basis of weight. Grade quality and size
are not related to one another.
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38. 1- Grading of eggs according to their size:
Several factors influence the size of an egg:
a- age of the hen, as the hen ages, her eggs increase in
size.
b- The breed of hen from which the egg comes.
c- Weight of the bird is another.
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39. Environmental factors that lower egg weights are :
a-heat,
b- stress,
c- overcrowding and
d-poor nutrition.
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40. GRADING OF EGGS ACCORDING TO
THEIR SIZE
GradeWeight
JumboOver 69g
Extra large64-69g
Large55-64g
Medium49-55g
Small42-48g
Peewee (mini)42g
N.B. Medium, Large and Extra Large are the sizes most commonly
available.
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41. GRADING OF EGGS ACCORDING TO
THEIR SIZE
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42. 2-GRADING OF EGGS ACCORDING TO THE
INTERIOR QUALITY AS WELL AS THE
CONDITION AND APPEARANCE OF THE
SHELL:
Eggs are graded to Class A, Class B and Class C (clean
unbroken egg). Class C includes all eggs, which do not
satisfy the requirements of Class A and Class B but are
suitable for the manufacture of foodstuffs for human use.
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43. All eggs, which do not fall into these classes, are classed
as "Industrial Eggs" and may not be used for human
consumption either as eggs or in the manufacture of
foodstuffs.
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44. GRADING OF EGGS ACCORDING TO THE
INTERIOR QUALITY AS WELL AS THE
CONDITION AND APPEARANCE OF THE
SHELLClass AClass BClass C
CuticleNormal, clean,
Undamaged
Dirty, Damaged
and Treated
Dirty, Damaged and Treated
ShellNormal, clean, undamagedNormal, undamagedCracked, Miss-shaped, Treated
Air cellDepth not exceed 7mm,
stationary
Depth not exceed 9mm,
Mobile
Depth exceeding 9mm, Mobile
or Damaged
AlbumenClear, Transparent, Gelatin-like,
Free from foreign bodies
Clear, Transparent, Free
from foreign bodies
Clear, No discoloration or
turbidity, small foreign bodies
YolkVisible on candling as a shadow
only without recognized outline,
No moving from center of egg on
rotation, Free from foreign
bodies
Visible on candling as a
shadow only, Free from
foreign , bodies
Distinct on candling, sided or
stuck, No discoloration, Small
foreign bodies
Germ cellVery slightVery slightVery slight
SmellFree from foreign odorsFree from foreign [ odorsFree from foreign odors
Dirty or broken eggs may not be graded.9/6/2020 Dr. Zeinab I. Ali 44

45. THE MICROBIOLOGY OF EGGS
1- Sources of egg contamination
Freshly produced egg is almost sterile or contaminated with
a very few number of microorganisms.
Contamination may be due to:
A) Congenital (Intrinsic factors)
B) Extragenital (Extrinsic factors)
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46. A) CONGENITAL (INTRINSIC
FACTORS)
- Microorganisms are introduced to the egg during its
formation in the ovary or oviduct, during bacteremia.
Microorganisms may localize in the ovary, which becomes
a focus of infection of newly formed eggs (e.g. Salmonella).
- Microorganisms may be forced into the genital tract from
the outside and thus may contaminate normal egg.
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47. B) EXTRAGENITAL (EXTRINSIC
FACTORS)
The eggshell is contaminated directly after laying while it is
hot, bacteria attaches during cooling of the egg. The
interior contents contract and microorganisms may aspire
through shell pores.
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48. Factors enhancing the Penetration of microorganisms
through the shell pores to the inside of the egg:
• Removal of cuticle.
• Presence of humidity and suitable temperature
• Contamination of the shell from the surrounding.
• Motility of contaminated organisms.
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49. • Improper washing is the most common source of
contamination when warm eggs are immersed in cold
contaminated water, the interior contents contract and
contaminated, water is aspired through shell pores into
the albumen.
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50. Duck eggs: Are usually highly contaminated because
• Ducks lay eggs near damp areas.
• Ducks pick up flies and other infected materials.
• The shell is very thin.
• The antimicrobial effect of the white deteriorates rapidly.
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51. N.B.
Microorganism that can enter the egg contents either
before or after laying are able to multiply rapidly as the yolk
is a highly nutritive medium and cause spoilage. If such
eggs are consumed raw or semi raw it may be responsible
for spread of sporadic or epidemic diseases.
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52. 2- Antimicrobial defense of the egg:
The defense is partly physical (shell & its membranes) and
partly chemical (the shell membranes & albumen).
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53. 1- Shell:
Although the shell of an egg is porous, the pores normally
are filled with organic material (bloom), which hinders the
entrance of microorganisms. The high incidence of rotting
is usually associated with washed eggs.
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54. 2- Shell membranes:
Each membrane consists of layers formed from a network
of keratin fibers acting as bacterial filters. Also shell
membranes contain lysozyme, which mainly affect Gram
positive and some Gram negative organisms.
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55. 3- Albumen:
Albumen contains substances with antibacterial action. The
most effective germicidal agent in the white is lysozyme.
(a). Lysozyme: Which lysis the cell wall of some
organisms. (Most effective against Gram positive bacteria)
(b). Avidin: Which binds biotin, a nutrient needed by
certain microorganisms, thus retard their growth (Depends
on bacterial requirement for this vitamin).
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56. (c)- Conalbumin (ovotransferrin): which units with iron,
zinc and copper and makes it unavailable, thus
microorganisms are unable to grow (Most effective against
spoilage bacteria)
(d)- Ovomucoid: Inhibit trypsin (Unknown role)
(e)- Flavoprotein: Binds riboflavin, making it unavaliable to
bacteria. Other inhibitors includes Ovoinhibitor,
Ovomacroglobulin, Cystatin.
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58. DISEASES, WHICH MAY
TRANSMITTED THROUGH EGGS
1- Salmonellae are of most concern in egg, other pathogens have
been isolated but they have not been found to be as important in
foodborne disease outbreaks.
Hen's egg —-— S. pullorum, S. montevides and S. anatum.
Duck's egg —-- S. typhimurium and S. dublin
N.B. Recently Salmonella entertidis has become a major concern, there
have been increasing outbreaks, and this infection has been reported
as transovarian contamination.
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59. DISEASES, WHICH MAY
TRANSMITTED THROUGH EGGS
2- Pathogenic organisms of emerging concern in egg and
egg products include Campylobacter jejuni, Listeria
monocytogenes and Yersinia enterocolitica, all are resistant
to Lysozyme.
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60. DISEASES, WHICH MAY
TRANSMITTED THROUGH EGGS
3- Other egg pathogens are Avian T.B., E. coli, Staph.
aureus and Strept. fecalis.
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