Group Title: Poultry Science mimeograph series
Title: Some factors to consider in washing shell eggs
Full Citation
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 Material Information
Title: Some factors to consider in washing shell eggs
Alternate Title: Poultry Science mimeograph series - University of Florida ; PY64-3
Physical Description: 5 p. : ; 28 cm.
Language: English
Creator: Tarver, Fred R. Jr. ( Fred Russell )
Donor: unknown ( endowment )
Publisher: Florida Agricultural Experiment Station
Place of Publication: Gainesville, Fla.
Publication Date: July, 1963
Copyright Date: 1963
Subject: Eggs -- Cleaning -- Florida   ( lcsh )
Eggs -- Quality -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: by Fred R. Tarver, Jr.
General Note: Caption title.
General Note: "July 1963."
 Record Information
Bibliographic ID: UF00094224
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 318812320

Full Text

/ Poultry Science Florida Agricultural
Mimeograph Series No. PY64-3 Experiment Station
200 copies Gainesville, Florida
July 1963


by Fred R. Tarver, Jr.
Assistant Poultry Husbandman
University of Florida

The egg may be its cleanest at the time of laying. The word clean has

reference to the absence of dirt on the shell. The shell's first contact

with dirt might be nesting materials or other type nesting devises. Clean

and dirty eggs alike need attention. Dirty eggs are a particular problem

when consideration is given the job of cleaning and economics. It is generally

conceded that some method of wet cleaning soiled eggs is more practical than

dry cleaning. Observations indicate that from ten to twenty-five percent of

the eggs produced under average farm conditions are soiled prior to the time

of gathering. This includes dirty and slightly dirty eggs. There exists a

potential annual cost of several thousand dollars to the poultry industry of

Florida. The main objective in cleaning the egg shell is to remove as near

as possible all visible and invisible dirt without endangering the eggs sales


As washing is considered the most applicable method for cleaning the

egg shell, it would be appropriate to point out some factors to consider

that can contribute to a superior cleaning job.

From the exterior shell surface inward, the structure of the shell has

first an outer shell coating referred to as the cuticle or mucin. This

material is deposited on the shell as the egg passes through the vagina of

the hens reproductive tract. Next, a layer referred to as the spongy layer.

*2 -

The mammillary layer and mammillary core are located between the spongy layer

and shell membranes. Lastly, the pores extend from the outer shell surface

to the outer and inner shell membranes. The pores are plugged with cuticle

which serves as a natural barrier against the invasion of micro-organisms.

The shell is also a natural barrier against the invasion of micro-organisms.

The shell membranes also serve in this same respect. If micro-organisms

find their way to the point of passing through the membranes, the egg meats

contain certain substances of which lysozyme is one that inhibits certain

micro-organisms. The micro-organisms are invisible agents or invisible dirt

that causes egg spoilage in the form of green rots, soured eggs, pink eggs,


Water is generally accepted as the carrier and solvent in the wet

cleaning of shell eggs. When water is used in the processing of a food

commodity such as the egg, it should be given consideration from at least

two aspects; 1) micro-biologically and, 2) mineral content. Micro-biologically,

water for food purposes should be potable or drinkable. This implies that the

water, either in the natural or treated form, is free of those micro-organisms

that are a health hazard. I would imagine that the major sources of water

available for use by Florida poultrymen would be a spring or well. It is

highly probable that such sources of water have never been examined bacterio-

logically. Surface or shallow subsurface sources of water should be looked

upon with some suspicion from the standpoint of bacterial contamination. In

some instances, the mineral content of water can reduce the effectiveness of

cleaning agents during the egg washing process. Hard water for example con-

tains a high content of calcium carbonate and other similar salts. Minerals

such as iron and magnesium can also impede the effectiveness of cleaning the


shell. In addition, they clear the way for the invasion of micro-organisms.

Furthermore, it is possible for a mineral such as iron to stain the shell

of eggs. Many of the mineral and bacteriological problems occurring with

water may be overcome by the application of certain chloronating equipment

and/or sequestering agents.

With the problem of dirt on egg shells and existing conditions in the

water, it would be well to discuss means of combating bacteria and obvious

dirt. These would include detergents and/or sanitizers. Since the shell

is predominant calcium carbonate and is alkaline or basic in nature, alkaline

detergents would be suitable for cleaning the egg shell because of the reduced

possibility of chemical reactions with the shell. Whereas in the case of

acid type detergents a chemical reaction can occur. Detergents designed for

the purpose of cleaning egg shells and used according to recommendations

will do an excellent job. But they are limited with respect to killing

bacteria. The sanitizer has the sole purpose of destroying bacteria. When

sanitizers are used in the proper concentration and this concentration main-

tained, the destructive power will be effectively demonstrated. Combinations

of detergent-sanitizers used according to directions will do a most effective

job. Recommendations for the concentration of sanitizer should not exceed

200 parts per million.

The style, manner and effectiveness of cleaning egg shells depends upon

the type of equipment employed. This may range from hand washing with a

damp cloth to that of continuous inline egg washer. The purpose of the

washing equipment is to bring the water, the detergent and sanitizer in direct

contact with the shell through an effective scrubbing action. The cleaning

operation should be completed in a minimum amount of time without damage to

the shell. Egg wash water temperature should be maintained between 1100 F
and 120 F. A short time exposure of the egg in water of this temperature


is affective in the removal of both the visible and invisible dirt. During

the washing operation, the affective strength of the detergent and the

sanitizer is gradually reduced. It is necessary to change or rotate the

supply of water and to maintain the recommended quantities of detergent and

sanitizer. After the eggs have been washed, it is considered a good practice

to rinse the eggs in clean water that contains a sanitizer. Afterwards, the

eggs are permitted to dry. As drying progresses, the sanitizer on the shell

becomes moze concentrated therefore providing a longer period of protection

against bacteria. It is essential that eggs be dried in a manner that will

prevent the development of water spots on the shell. During the drying period,

the containers holding the eggs should not absorb water. Such containers

might include plastic flats, rubber coated baskets or an inline conveyor belt

(plastic, rubber, etc.). The materials in which the eggs are packed should

be dry and clean to further enhance the protective power given by the sani-

tizer. Eggs handled in such a manner can be expected to have a shelf life

similar to that of eggs which have not been washed.

Even though we continuously strive for the production of clean eggs,

this Utopia seems to remain distant. Many problems have been encountered

as a result of washing eggs. A few years ago many washed eggs placed in cold

storage would ultimately be thrown away because of bacterial decomposition

of the egg meats. Even at the present time with the hot summer months,

bacteria and lack of refrigeration, eggs may be destroyed through the genera-

tion of gas produced by bacterial action. In any egg washing operation,

water temperature should be higher than the egg. This permits the egg con-

tents to expand whereas if the reverse is true the meats would contract thus

pulling wash water through the shell into the egg meats.

- 5 -

In many instances the fact may be neglected that we are working with a

food commodity, an item that will be consumed. This should remain uppermost

in our minds when handling eggs or any other food item for human consumption.

At times, many may feel that this is just another expensive operation.

It is totality of factors that contribute to an efficient quality control

program not one isolated factor.

Some common alkaline detergents and sanitizers are listed below:

Alkaline detergents:

Sodium carbonate

Sodium metasilicate

Sodium hexametaphosphate

Sodium or potassium soaps

Sodium hydroxide


Tetra sodium pyrophosphate




Quaternary ammonium compounds

Hydrogen peroxide

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