Contamination and spoilage of eggs can occur through several means: 1. Eggs become contaminated after laying through contact with feces, cages, wash water, or improper handling. 2. As eggs age, their contents naturally change through loss of moisture and thinning of egg whites. 3. Microorganisms can cause spoilage if they contaminate the shell and penetrate into the egg, growing through the whites and potentially reaching the yolk. 4. Bacterial spoilage results in rots of different colors like green, colorless, or black rots caused by various Pseudomonas and Proteus species. Mold growth can also cause pinspot molding or fungal rotting.

1. CONTAMINATIO
N AND
SPOILAGE
OF EGG
Ramya.H
1st year M.Sc. Food & Nutrition

2. CONTAMINATION OF EGGS
Freshly laid eggs are sterile.
Shells soon become contaminated by
1. fecal matter of hen
2. Cage or nest
3. Wash water if eggs are washed
4. Handling
5. Material in which the eggs are packed.

3. CHANGES NOT CAUSED BY
MICROORGANISMS
 Untreated eggs lose moisture during storage and
hence lose weight.
 Shrinkage shown by the size of the airspace or air
cell of the egg.
 Changes in the physical state of the contents of
the egg seen by candling or breaking.
 As the egg ages, Egg white becomes thinner and
more watery and yolk membrane weakens.
 The poorer the egg, more movement of the yolk.
 Normal pH of egg-7.6 to 9.5,storage increases
the alkalinity of the egg white.

5. CHANGES CAUSED BY
MICROORGANISMS
• Tasks to be accomplished by causal organisms to
cause spoilage :
(1) contaminate the shell
(2) penetrate the pores of the shell to
membranes (shell must be moist)
(3) grow through shell membranes to reach
white
(4) grow in egg white to reach egg yolk.
• Time taken to penetrate varies with organism &
temperature.
• In general, more spoilage is caused by bacteria
than by molds.

6. BACTERIAL SPOILAGE OF
EGGS
• Bacteria need to overcome the anti – bacterial
properties of albumen to cause spoilage of eggs.
• Also, they use the protein complexes as a source
of nitrogen for growth.
• Bacterial spoilage is called as rots. Three chief
ones are green rots, colorless rots & black rots.
• The other two are pink rots & red rots.

7. GREEN ROTS
• Caused by Pseudomonas fluorescens (grows at 0΄C).
• Egg white in early stages, becomes bright green in
color during Later stages, yolk disintegrates &
blends with white.
• Odour is lacking or is fruity or sweetish.
• Contents of egg fluoresce strongly under UV light.

9. COLOURLESS ROTS
• Caused by Pseudomonas, Acinetobacter,
Alcaligens.
• Detected by candling.
• Yolk in later stages, disintegrates or shows a white
incrustation.
• Odour varies from a scarcely detectable to fruity
to highly offensive.

10. BLACK ROTS
• Most commonly caused by a species of Proteus.
Pseudomonas & Aeromonas can also cause this.
• Proteus melanovogenes causes black coloration
yolk & dark color in white.
• Caused when egg is stored at temp. higher than
the ordinary.
• Gas pressure develops in the egg.
• Putrid odour (hydrogen sulfide is evident).

11. BLACK ROT

12. PINK ROTS
• Less often; caused by strains of Pseudomonas.
• They resemble colorless rots ; except for the
pinkish precipitate on the yolk & a pink colour in
the egg white.

13. RED ROTS
• Most infrequently occurring one.
• Caused by a species of Serratia.
• Odour is mild & not offensive.

14. FUNGAL SPOILAGE OF
EGGS
• Spoilage of eggs by fungi goes through stages of
mold growth. The stages give the defects their
names.
• There are two stages :
(1) Pin Spot Molding
(2) Fungal Rotting
• Molds that cause spoilage of eggs include species
of Penicillium, Clodosporium, Sporotrichum,
Mucor, Alternaria & Botrytis.

16. PIN – SPOT MOLDING
• Very early mold growth.
• Small, compact colonies of molds appear on the
shell & usually just inside it.
• Colour varies with the kind of mold :
(1) Penicillium species cause yellow or blue or
green spots inside the shell.
(2) Clodosporium species give dark – green or black
spots.
(3) Sporotrichum species give pink spots.

17. FUNGAL ROTTING
• Final stage of spoilage.
• Mycelium of the mold has grown through the
pores or cracks in the egg.
• Jellying of egg white is seen.
• The hyphae of the mold may weaken the yolk
membrane enough to cause its rupture. After
this, growth is stimulated by food released from
the yolk.

18. DEVELOPMENT OF OFF -
FLAVOURS
• Mustiness may be caused in eggs by the bacteria
sometimes.
• The growth of Streptomyces near the egg may
produce earthy or musty flavors that are
absorbed by the egg.
• A hay odour is caused by Enterobacter cloacae.
• Fishy flavors are produced by strains of E.coli.

20. METHODS OF
PRESERVATION
There are various methods that help prevent
spoilage of eggs :
• Use of heat
• Chilling
• Freezing
• Use of preservatives
• Use of irradiation

21. THANK YOU