Title: VETERINARY INSPECTION OF EGG AND EGG PRODUCTS
1VETERINARY INSPECTION OF EGG AND EGG
PRODUCTS
2Formation-developing of egg
- The yolk of the egg is the matured ovum that is
formed in the left ovary of the poultry. When the
ovum reaches the appropriate size, it is released
from the follicle and is fallen into the funnel
shaped diverticulum of the oviduct. The ovulation
is 30-60 minutes after the laying of the previous
one. The ovum is surrounded by the vitelline
membrane.
3- The ovum advances rotating in the lumen of
oviduct. While advancing, from the secretum of
closely located glands, the inner tenuous, the
middle dense and the outer tenuous albumen layers
and the chalaza that are between the middle layer
and inner shell membrane are formed. In the
isthmus and in the next part of oviduct, the
double shell membrane and the calcareous shell
are formed, respectively. The latter will be
covered by the cuticle just before laying. The
double shell membrane is separated at the blunted
end of the egg after laying).
4- Physico-chemical properties of egg
- The chemical composition of egg
- whole egg albumen yolk of egg
- water 73. 6 87.9 48. 7
- egg protein 12.8 10.6 16.6
- fat 11.8 - 32.6
- carbohydrate 1.0 0.9 1.0
- ash 0.8 0.6 1.0
- In the yolk there are significant quantities of
vitamin A, pigment (carotinoids) and lecithin
(12).
5- UGF-s (unidentified growth factors) (Zoo-animals)
- The egg contains a significant quantity of
enzymes (trypsine, erepsine, lipase). Their
quantity however, is increased significantly at
the beginning of development of the embryo.
Special importance has the lisosyme located in
the albumen layer. It inhibits the development of
Gram bacteria that penetrate through the pores
into the egg. The inhibitory action of lisosyme
is inactivated by the yolk (in eggs, in which the
yolk and albumen is mixed together, bacteria can
proliferate well).
6Albumen layers of egg precipitate at 57-60 C
while the yolk at 65-70 C. The pH of albumen
layers of fresh egg is 7.6. Releasing the high
carbon dioxide content in contact with air, the
pH of egg is elevated up to 9.4-9.6. Thus, this
is not the result of bacterial processes! The pH
of the yolk is 6.0 in fresh egg. Elevated yolk pH
indicates rotting.
7The disorders of the shell are hollows,
protrusions, disjunctions up to distorted forms.
The candle-broken egg is formed during the
development of the egg. Upon a mechanical effect,
the developing egg is ruptured, later further
calciferous layers will cover this injury. The
disorder can be detected only by translumination.
The calcification of the shell is often disturbed
due to the illness of the oviduct or systemic
disorder.It is not a disorder but severe
hygienic insufficiency if the shell of egg is
contaminated with faeces or blood.
8Disorders of the yolk are the complete absence of
yolk, the presence of two or more yolks, the ovum
may be separated in different measure.Sometimes
spots can be seen on the vitelline that mostly is
derived from water closed under the vitelline
membrane during development. Sometimes, for
unexplained reason, the yolk is greenish and is
called grass egg. On the surface of yolk often
red spots can be observed deriving mainly from
the oviduct. This is the blood spotted egg. The
meat spots are lighter in colour and are related
to tissue fragments derived from the oviduct and
this is qualified similarly to the blood spotted
egg. Certain parasites may be found in the egg.
Though, they are not harmful but degustating.
9Disorders developing during storageThe
vitelline membrane is thinning and might be
ruptured during storage. The result is the egg
with mixtured yolk and albumen that is not
suitable for consumption. The dense part of
albumen is diluted and after a certain time only
thin albumen is present (sticked yolk-egg).The
water loss is gradually developing through the
pores leading to the enlargement of air space.
This process, at 37 C and 50 relative humidity
can reach the air-dry condition. An
intermediate state of the process is the swimming
egg.
10During storage, enzymes generate H2S, NH3 and
volatile fatty acids.The egg is frozen at - 0.5
C and it becomes unsuitable for further
storage.Avoid the big differences in temperature
during storage, because the egg is sweated,"
promoting the proliferation of bacteria.Sometimes
the egg is spoiled during storage. The green
rotting (in basic medium) is caused by
Pseudomonas species that are penetrated into the
egg from faeces. They cause also red rotting (in
acidic medium). The yolk becomes black and hard
(black rotting), the albumen is evil-smelling
upon the effect of Proteus spp. (e.g. vulgaris).
Yeasts can also penetrate into the egg during
storage.
11In the fertilised egg, the germ may start
developing at low storage temperature of 37-38
oC. Under this condition after a certain time the
embryo dies and the blood-ring egg develop that
is unsuitable for human consumption.The
examination of the egg (BATCH examination)
12- The disorders of the fresh egg
- Disorders due to abnormal development of egg.
- Disorders caused external factors.
- Disorders abnormalities originally during
storage. - The disorders of the fresh egg are present
already at the moment of laying. Though, these
eggs are fit for human consumption but are
excluded from distribution.
13- Methods
- Translumination
- Observation
- Breaking up (each 10th of sample is broken up)
14- Most of the disorders of eggs can be seen only if
the egg is candled (transluminated). This can be
carried out individually or in industrial scale.
In the individual procedure, the egg is kept
between the thumb and forefinger of left hand in
horizontal position and is transluminated by
light coming from a light source having slit.
During transluminating, the egg is turned around
its horizontal and vertical axises. In the
industry, the transluminator is built in a
defined point of the belt-conveyor of
classification. Approximately 100 eggs are
examined simultaneously and the work requires to
have good experience. Under normal conditions,
the yolk and albumen parts are closely homogenous
materials, the yolk might be slightly darker. The
air space has a size described in the Standard.
15The inside of the egg can also be examined after
breaking it. By opening the egg, it is possible
to observe its organoleptic condition, the
arrangement of parts of yolk and albumen and
determine the so called indices. Rotting can be
identified by translumination while bacterial
examination can be carried out only after
breaking the egg.In case of abnormality, the
further inspection is individual.
16Rotting is caused by micrococci, coliforms,
aerobe sporforming bacteria, Clostridia and
Flavobacteria. The spoilage of egg stored in
storage houses often is induced by moulds
(Penicillium, Cladosporium, Mucor and Aspergillus
species).
17Normal fresh egg
18The air chamber is smaller than 3 mm, immobile
and having regular shape.The albumen is clear,
the postion of yolk is central, not definitely
demarkated, spot-less
19Shrinken egg
20The air-cell is greater than 5 mm.The
borderlines of the yolk can be better seen.
21Sticked yolk
22The yolk is sticked (adhered) to the shell and it
cannot be separated from shell
23Mould-spotted egg
24Mould spots are formed at the inner side of the
shell.The egg has mouldy taste and smell.
25Egg with mixed yolk and albumen
26Due to decompostion or rupture of the vitelline
membrane, the yolk and albumen is mixed
27Grass-egg
28The yolk and the albumen are greenish with
different intensity.The taste is normal.
29Blood-spotted egg
30Blood spot on the vitelline membrane deposited
during the formation of the egg
31Ruptured egg seen only by translumination
32Slight rupture on the shell that can be seen only
by translumination
33Red rotting
34The rotted egg is redish-brown at
translumination.The yolk of rotted egg is mixed
with the albumen.
35Black rotting
36The egg with advanced rotting is blackish at
translumination.The egg can be exploded and
evil smelling.
37The egg of the hen may be infected with
salmonella. The wide-spread infection of our
poultry stocks is well known and it is maintained
by the feed. Though, the juice-egg can be
prepared in a special way to avoid the
contamination of the shell by faeces, yet the
contamination with some salmonellas may occur.
Such a small number of microbes usually do not
cause food intoxication because of the lisosyme
content of the cuticle and albumen, furthermore
the disinfection of the shell before breaking and
the storage at an appropriate low temperature
inhibit the proliferation of salmonellas. A
completely different issue is the non-fresh egg
removed by translumination on day 7 of hatching.
It must not use for direct consumption only for
the preparation of juice-egg.
38Judgement of egg and egg-preparations
39EggCondemned for human consumption Infertile
hens egg. The hen egg is infertile if it was
withdrawn from the hatchery after the 7th day of
incubation. At withdrawal of hatched egg of
other poultry-species disregarding the day of
withdrawal. Broken and organoleptically
disordered eggs, those that are mould-spotted,
rotted or having mixed yolk and albumen,
blood-ring, parasites or otherwise
degusting. Eggs infected with pathogen bacteria
or the number of facultative pathogen or
saprophyte bacteria or the residue level is over
the predetermined value laid down in regulations
or contaminated with other foreign material.
40Approved for human consumption (after
heat-treatment)If the egg or its shell is
contaminated, ruptured or depressed, or having
reduced, swimming, floating yolk, or blood
spotted or meat spotted, or frozen.Egg
productCondemned for human consumptionIf the
egg-preparation is prepared from water-birds egg
or it was treated with a prohibited compound (or
it is added to the preparation).
41Trade with egg or egg preparations Prohibited
to sell of hatched, broken, washed or dry-cleaned
eggs in market place or at farm. Eggs originated
from different poultry species must not be mixed
during marketing. Disinfected and unwashed eggs
must not be mixed or marketed as preserved egg.
The fact of preservation must be labelled on the
collective-package. Marketing non-hens egg, the
name of the given species must be written in an
attention drawing manner at place of selling.
42- In case of duck or geese egg, the following
massage board must be constructed and exhibited
(it is written with letter size of at least 20
mm) - The egg can be consumed only following 10
minutes of boiling or after well-baking
43Laboratory examination of egg and egg produts
- Entrobacteriaceae
- m 10 cfu/g
- M 100 cfu/g
- 3-OH-butyric acid 10 mg/kg
- Succinic acid 25 mg/kg
- Lactic acid 1000 mg/kg