Practice Veterinary InspEggs

8/3/2019 Practice Veterinary InspEggs

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VETERINARY INSPECTION

OF EGG AND EGG PRODUCTS


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Formation-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 releasedfrom 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 vitellinemembrane.


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The ovum advances rotating in the lumen of oviduct.

While advancing, from the secretum of closely locatedglands, 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 doubleshell 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).


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Physico-chemical properties of egg

The chemical composition of egg

whole egg albumen yolk of egg

water 73. 6 87.9 48. 7egg 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%).


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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).


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Albumen layers of egg precipitate at 57-

60 C while the yolk at 65-70 C. The pHof albumen layers of fresh egg is 7.6.

Releasing the high carbon dioxide

content in contact with air, the pH of eggis 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. Elevatedyolk pH indicates rotting.


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The 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 isruptured, 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 insufficiencyif the shell of egg is contaminated with faeces or

blood.


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Disorders 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, theyolk 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.


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Disorders developing during storage

The 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 thinalbumen 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.


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During storage, enzymes generate H2S, NH3 and volatile fatty

acids.

The egg is frozen at - 0.5 C and it becomes unsuitable forfurther 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 ofProteus spp. (e.g. vulgaris). Yeasts can also

penetrate into the egg during storage.


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In the fertilised egg, the germ may start

developing at low storage temperature of37-38 oC. Under this condition after a

certain time the embryo dies and the

blood-ring egg develop that isunsuitable for human consumption.

The examination of the egg (BATCHexamination)


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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 humanconsumption but are excluded from distribution.


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Methods:

Translumination

Observation

Breaking up (each 10th of sample is broken up)


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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 betweenthe 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.


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The inside of the egg can also be examined afterbreaking 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 bytranslumination while bacterial examination can be

carried out only after breaking the egg.

In case of abnormality, the further inspection is

individual.


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Rotting is caused by micrococci,coliforms, aerobe sporforming bacteria,

Clostridia and Flavobacteria. The

spoilage of egg stored in storage housesoften is induced by moulds (Penicillium,

Cladosporium, MucorandAspergillus

species).


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Normal fresh egg


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The 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


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Shrinken egg


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The air-cell is greater than 5 mm.

The borderlines of the yolk can be better seen.


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Sticked yolk


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The yolk is sticked (adhered) to the shell

and it cannot be separated from shell


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Mould-spotted egg


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Mould spots are formed at the inner side of

the shell.

The egg has mouldy taste and smell.


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Egg with mixed yolk and albumen


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Due to decompostion or rupture of the

vitelline membrane, the yolk andalbumen is mixed


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Grass-egg


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The yolk and the albumen are greenish with

different intensity.

The taste is normal.


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Blood-spotted egg


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Blood spot on the vitelline membrane

deposited during the formation of theegg


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Ruptured egg seen only by

translumination


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Slight rupture on the shell that can

be seen only by translumination


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Red rotting


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The rotted egg is redish-brown at

translumination.

The yolk of rotted egg is mixed with

the albumen.


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Black rotting


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The egg with advanced rotting is blackish at

translumination.

The egg can be exploded and evil smelling.


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The egg of the hen may be infected with salmonella. The

wide-spread infection of our poultry stocks is well known andit 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 notcause 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.


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Judgement of egg and egg-

preparations


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Egg

Condemned 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 isover the predetermined value laid down in regulations or

contaminated with other foreign material.


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Approved for human consumption (after heat-

treatment)

If the egg or its shell is contaminated, ruptured ordepressed, or having reduced, swimming, floating

yolk, or blood spotted or meat spotted, or frozen.

Egg product

Condemned for human consumption

If the egg-preparation is prepared from water-birdsegg or it was treated with a prohibited compound (or

it is added to the preparation).


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Trade 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 atplace of selling.


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In case of duck or geese egg, the followingmassage 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


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Laboratory 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

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Practice Veterinary InspEggs