EGG QUALITY DETERIORATION AND FACTORS AFFECTING EGG QUALITY

EGG QUALITY DETERIORATION AND
FACTORS AFFECTING EGG QUALITY
11/19/2020GURRAM SRINIVAS

EGG QUALITY DETERIORATION
Changes occur after laying:
 The rate of deterioration is closely related to the loss of
CO2 through the shell and increase alkalinity of egg
contents.
 The higher the temperature the higher the loss of CO2.
 The pH of the white may rise from about 7.6 in a freshly
laid egg to high as 9.0 to 9.7 within few days (due to loss of
CO2 ).
 The white become thinner.

Why the white become thinner?
 The rise in pH allows the electrostatic complex between
lysozyme and ovomucin to break.
 Breaking of disulphide bonds in ovomucin has been
suggested as a factor in the thinning of egg white.
 The thinner white cannot withstand the yolk centered in
the egg. In addition the white became yellow.
 The vitelline membrane which confines the yolk stretches
due to water passage from the white to the yolk.

 The yolk becomes enlarged and flattened. The
chalazae become detached allowing the yolk to move
freely within the egg.
 The free yolk may rest against the shell leading to
sided or stuck yolk or may be ruptured leading to
spreading yolk
 Air cell enlarged due to the water evaporates from
liquid contents through the shell pores and the air
replaces the water lost.
 The egg becomes extremely suitable for invasion by
microorganisms.

Microbial changes:
Rot and mold:
 These develop in some eggs by the presence of
microorganisms like bacteria, mold and yeast within the
egg.
 These organisms mainly enter the egg after laying from
dirty and moist shell. Washing increase the case due to
removal of the bloom and help the microorganisms to
invade the egg contents through the pores.

Rotten eggs:
 These eggs normally contain a mixed infection of Gram-
negative and a few Gram-positive organisms also.
 Alcaligenes, Achromobacter, Pseudomonase, Serratia,
Hafnia, Citrobacter, Proteus and Aeromonase.
 Bacteria causing abnormal flavors (taint):
• Proteus vulgaris -------------- Foul odor.
•Pseudomonase -------------- Ammoniacal odor.
• Bacillus subtilis ------------- H2S production.
• Eggs may pick up flavors from strange odors in the storage
area.

Organisms produce pigments
Organism Type of rot
Proteus sps Black rot
Aeromonas Liquefacians Black rot
Serratia marcescens Red rot
Pseudomonase maltophilia Green rot
Pseudomonase fluorescens Fluorescent green changed to pink
Pseudomonase putida Fluorescent green rot
Pseudomonase aeruginosa Fluorescent blue rot
Flavobacterium Yellow rot
Alcaligens Colorless

Mold spoilage:
 Less important than bacteria, only under humid
conditions the shell could be clothed with mycelium
“Whiskers”.
 Hyphae penetrate the pores and grow on the shell
membranes associated with gelling of the albumen
around patches of mycelia.
 On candling these show up as dark or colored patches or
rings.
 Further growth results in the complete gelling of the
albumen and the break down of yolk membrane.
 Cladosporium and Sporotrichum the most common
types.

FACTORS AFFECTING EGG SHELL
QUALITY
1.BIRD STRAIN:
 Different strains of laying hen vary signiﬁcantly in egg shell
quality, egg size and production
 It is known that eggs from white-egg-laying hybrids
demonstrate better egg shell quality compared to brown egg
hybrids
2.BIRD AGE:
 Egg shell quality decreases as birds grow older
 Inability of the hen to produce an increased amount of egg
shell is related to the activity of 25-hydroxycholecalciferol--
hydroxylase, an enzyme involved in calcium homeostasis

3.NUTRITION:
 Each egg shell contains up to 3grams of calcium. Therefore,
the diet of hens must contain adequate calcium in a form
that can be utilized efficiently.
 The ratio of calcium to phosphorus in the diet is important
as high levels of phosphorus may interfere with the
absorption of calcium from the gut, resulting in reduced
shell quality
 The levels of calcium in feed need to be increased during
the rearing period, 7 to 10 days prior to the appearance of
the ﬁrst egg

 Adequate levels of Vitamin D are necessary for calcium
metabolism
 Low levels of vitamin A may increase the incidence of
blood spots, which reduce the internal quality of the egg
 Adequate levels of Vit-C, E in summer months
 Water quality may inﬂuence egg shell quality. Water
containing high levels of electrolytes (saline drinking
water) may have long-term negative effects on egg shell
quality
 Provision of cool drinking water can improve egg shell
quality in heat-stressed hens

 Contamination of feed with mycotoxins has the potential
to reduce production and egg shell quality.
4. STRESS:
 The high temperatures experienced during the summer
can result in smaller eggs and reduced shell quality
 It also reduce the activity of carbonic anhydrase, an
enzyme which results in the formation of bicarbonate
which contributes the carbonate to the egg shell

5. DISEASE:
 Infectious bronchitis , Egg drop syndrome affect shell
quality
 Newcastle disease can cause temporary rough shells
 Pseudomonas, Proteus, and Escherichia Contaminated
eggshells produce off odors.
6.HUMIDITY:
Porous shells have been reported to come from areas with
high relative humidity

7.CHEMICALS:
 Shell color can be affected by nicarbazin which causes hens
who normally lay brown-shelled eggs to lay white-shelled
ones.
 Aureomycin can cause yellow shells.
 Eggs washed in excessively high chlorine concentrations
sometimes have a brownish cast.

8.PRODUCTION SYSTEM:
 Various farming systems, e.g.,battery-cages, deep litter or
free-range, have a significant impact on eggshell quality.
 It was observed that percentage of cracked eggs is lowest
in furnished cages followed by conventional cages.
 Eggs from caged hens demonstrate better shell quality,
especially in terms of strength and thickness, higher egg
shape index values, yolk index and albumen quality
expressed especially by Haugh units, compared to eggs
from hens raised in deep-litter or on free-range farms
 Microbial contamination of egg shell is more in deep litter
system.

FACTORS AFFECTING EGG INTERNAL
QUALITY
1.STORAGE:
 Albumen height and Haugh units decrease with storage
time and this decrease occurs more quickly at higher
temperatures
 During storage of eggs, the pH of the albumen increases
and this is thought to be related to the deterioration of
albumen quality
 During egg storage, the quality of the vitelline membrane
declines, making the yolk more susceptible to breaking

2.HEN STRAIN AND AGE:
 The age of the hens is also important as albumen quality
declines with bird age. Albumen quality is also effected by
the strain of bird and genetic selection
3.INDUCED MOULT:
 Albumen quality in older hens has been shown to improve
following an induced moult

4.NUTRITION:
 Albumen quality decreasing with increasing dietary protein
and amino acid content, increases with increased dietary
lysine concentration, increasing with ascorbic acid and
vitamin E supplementation, especially at high ambient
temperatures
 Excess of cottonseed meal in rations developed for
chickens under organic feeding causes discolored yolks
brownish discoloration.
 Platinum-colored yolks can be caused by vitamin A or
xanthophyll deficiency, bacteria, or heavy infestations of
round- worms

5.DISEASE:
 The main disease of laying hens that has been reported to
affect albumen quality is infectious bronchitis virus which
may cause a decrease in quality and more variable
albumen quality
 Moulds occasionally created a problem when eggs were
stored with high humidity. The mycelium or mold filaments
can penetrate eggshell pores and contaminate the interior
contents

REFERENCE:
 Poultry Products Technology, Third Edition by George J.
Mountney and Carmen R. Parkhurst

THANK YOU

EGG QUALITY DETERIORATION AND FACTORS AFFECTING EGG QUALITY

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EGG QUALITY DETERIORATION AND FACTORS AFFECTING EGG QUALITY