Microbial spoilage of egg.

1. MICROBIOLOGY OF EGGS
Dr. Zanwar S. R.
DEPT OF FIM,
MGMCFT, Gandheli.

2. Contamination
 Most freshly laid eggs are sterile.
 contaminated by
1. fecal matter from the hen,
2. the cage or nest,
3. wash water
4. handling
5. the material in which the eggs are
packed.
 Salmonella sps may be on the shell or in
the egg as laid, build up during

3. Changes Not Caused by
Microorganisms
 Untreated eggs lose moisture during storage and hence
lose weight.
 The amount of shrinkage is shown to the candler by the
size of the air space or air cell.
 The change in the physical state of the contents of the
egg, as shown by candling or by breaking out the egg.
 As egg ages, the white of the egg becomes thinner and
more watery and the yolk membrane becomes weaker.
 During storage, the alkalinity of the white of the egg
increases.
 Any marked growth of the chick embryos in fertilized
eggs also serves to condemn the eggs.

4. Changes Caused by
Microorganisms
 To cause spoilage of an undamaged
shell egg, the causal organisms must do
the following:
(1) contaminate the shell,
(2) penetrate the pores of the shell to the
shell membranes
(3) grow through the shell membranes to
reach the white
(4) grow in the egg white to reach the yolk,
 Generally, more spoilage of eggs is
caused by bacteria than by molds.

5. Bacterial Spoilage of Eggs
I. Green rots
 Caused chiefly by Pseudomonas fluorescens
 Rot is so named because of the bright-green color
of the white during early stages of development.
 Odor is lacking or is fruity or "sweetish.“
 The contents of eggs so rotted fluoresce strongly
under ultraviolet light.

7. 2. Colorless rots
 Caused by Pseudomonas,
Acinetobacter, Alcaligenes, certain
coliform bacteria.
 Detected by candling.
 yolk usually disintegrates or at least
shows a white incrustation.
 The odor varies from fruity to "highly
offfensive."

8. 3. Black rots
 Most commonly caused by Pseudomonas,
Proteus & Aeromonas sps.
 Proteus melanovogenes causes an
especially black coloration in the yolk and a
dark color in the white.
 The odor is
putrid, with
hydrogen sulfide
evident, and gas
developed.

9. 4. Pink rot
 Pink rots are caused by strains of
Pseudomonas.
 They resemble the colorless rots,
except for a pinkish precipitate on the
yolk and a pink color in the white.
5. Red rots
 Red rots caused by species of
Serratia.
 Mild in odor.

10. Fungal Spoilage of Eggs
 Fungal spoilage of egg follow the
stages namely,
1. Pin molding
2. Superficial fungal spoilage
3. Fungal rotting
4. Off flavor development

11. 1. Pin spot molding
 Very early mold growth
 It is termed pin-spot molding because of
the small, compact colonies of molds
appearing on the shell and usually just
inside it.
 The color of these pin spots varies with
the kind of mold.
 Penicillium sps cause yellow or blue or
green spots.
 Cladosporium sps give dark-green or
black spots.
 Sporotrichum sps produce pink spots.

12. II. Superficial fungal spoilage
 In storage atmospheres of high humidity a
variety of molds may cause superficial
fungal spoilage,
 First in the form of a fuzz or "whiskers"
covering the shell & later as more luxuriant
growth.
 Molds causing spoilage of eggs include
species of Penicillium, Cladosporium,
Sporotrichum, Mucor, Thamniidium,
Botrytis, Alternaria, and other genera.

13. III. Fungal rotting
 The final stage of spoilage by molds.
 The mycelium of the mold has grown
through the pores or cracks in the egg.
 Jellying of the white may result, and colored
rots may be produced.
 The hyphae of the mold may weaken the
yolk membrane enough to cause its
rupture, after which the growth of the mold
is stimulated greatly by the food released
from the yolk.

14. IV. Off flavor
 Off-flavours sometimes are developed in
eggs.
 Mustiness may be caused by any of a
number of bacteria (Achromobacter,
Pseudomonas).
 The growth of Streptomyces may produce
musty or earthy flavors that are absorbed by
the egg.
 Molds growing in the shell also give musty
odors and tastes.
 A hay odor is caused by Enterobacter
cloacae.
 Fishy flavors are produced by Escherichia

15. Preservation
 Use of low temperatures
(Chilling, freezing)
 Preservation by drying
 Use of preservatives
 Use of Irradiation
 Use of heat

16. Microbiology of Poultry

17. Contamination
 The skin of live birds may contain numbers of
bacteria.
 other organisms from feet, feathers, and feces.
 Contamination during washing, plucking, and
evisceration.
 The types of organisms isolated depend on where
samples are taken and on the stage of processing.
 Salmonella-positive birds is common and range
from 0 to 50 percent.
 There is also a high incidence of Campylobacter
jejuni in poultry processing plants and on the
processed bird.

18. Spoilage
 Bacteria are the chief cause of spoilage.
 Intestines are primary source of these
organisms.
 Eviscerated poultry held at 100 C or below is
spoiled mostly by Pseudomonas & yeasts, e.g.,
Torulopsis and Rhodotorula.
 Above 100C, Microococci, Alcaligenes and
Flavobacterium grows.
 Iced, cut-up poultry often develops a slime with
"tainted," "acid," "sour," or "dishraggy odor" by
species of Pseudomonas & Alcaligenes.

19. Preservation
 Use of Heat
 Use of low temperature
 Use of Preservatives
 Carbon dioxide Atmosphere
 Use of Irradiation