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Eggs
eggs

Introduction

An egg is literally and metaphorically a bird in a shell.  The egg functions as a provision cupboard for the unborn bird and since the beginning of mankind, food for human beings.
Nowadays chicken eggs are the most common, however, eggs from other birds are sometimes used such as quail, plover, goose or ducks’ eggs.  In this chapter when the word ‘egg’ is used, it should be taken to mean a chicken egg.

Function of eggs

Few products are as indispensable in the kitchen as eggs.  Their versatility can be expressed more clearly by the following summary of their uses:  They can be used as:

  • Independent dishes, prepared in various ways: boiled, poached, scrambled, fried or as an omelette
  • Garnishes for example in salads, cold dishes or canapés
  • Thickening for example soups
  • Binding agents (and emulsion) for sauces
  • Raising agents in soufflés, cakes, éclairs and other baking products
  • Aerators in mousses, bavarois, meringues and other desserts and baking products
  • Coating when panning fish, meat or croquettes
  • To glaze for example puff pastry
eggs with mayonaise

The nutritional value of eggs

Despite the fact the eggs are composed of 75% water, their nutritional value is extraordinary. An egg, excluding the shell, is composed of water, fat and proteins.  The yolk contains most of the proteins and all the fat.  The yolk fat consists mainly of singular unsaturated fat, which is unfavourable for the cholesterol levels in the human blood.   A raw egg contains per 100gram 333-milligram cholesterol.  This is more than for example full fat cheese or butter.  Eggs contain the important vitamins A, B1 and B2 and the minerals iron, phosphor and calcium.  The exact amounts depend naturally on the size of the egg.

 

Proteins

Fat

Cholesterol

Whole eggs

21,6 gram

9,8 gram

333 mg

Egg white

10,5 gram

0 gram

0 mg

Egg yolk

16,7 gram

32,6 gram

1226 mg

(The proportions of fat-protein per 100 grams raw chicken egg)

Protein

7,5 gram

Fat

5,9 gram

Carbohydrate

   0 gram

Vitamin A

0, 1 mg

Vitamin B complex

0,06 mg

Calcium

27 mg

Phosphor

100 mg

Sodium

65 mg

Iron

1 mg

Energy

83 kCal/347 kJ

(The nutritional value of a chicken egg weighing 60 gram)

Cholesterol

Egg yolk consists mainly of animal fat.  Animal fat contains saturated and unsaturated fatty acids.  Saturated fatty acids are rich in cholesterol, a material that has gained much attention over the last few years as high amounts of cholesterol can be damaging to human health.  Cholesterol is not only found in eggs but in offal such as liver and kidneys and shellfish such as prawns and mussels.
Cholesterol is also found in milk, butter and other dairy produce.
Cholesterol is a material, which is necessary for the building of cells and the production of hormones.  It is essential for the good functioning of the human body.  The body produces cholesterol naturally and in most cases breaks down the excess.   However, in some cases it builds up in the blood creating a greater chance of heart and vascular illnesses.  People with high blood cholesterol are given the advice to drastically cut down the consumption of cholesterol.  Some specialists however, are of the opinion that it has not been conclusively proved that food with a high percentage of cholesterol is directly responsible for a high blood cholesterol level.  Cholesterol levels can be contributed to other important factors such as genetic, (over-) weight, stress, lack of physical exercise and smoking.
As far as nutrition is concerned, the amount of saturated fat in a diet can play an important part in controlling cholesterol levels.  According to the latest research it is not so important what the composition of the fat in a product is as the amount of fat in food consumed in general.

Conclusion:  In the kitchen, in principle it is not necessary to worry about the cholesterol levels of the products that are used.  It is more important for the customers that both animal and vegetable fat is used with great care and used as little as possible.

Purchasing eggs

Buy eggs from a reliable source – they must be used within 21 days between laying and cooking.  In the catering business, regular deliveries of eggs are essential to avoid storage problems of such a sensitive commodity.

When purchasing eggs, several factors deserve attention:

  1. The type of product
  2. The physical condition
  3. The quality identifying marks
  4. The price

1.         The type of product

The choice of eggs on the market has increased remarkable the last few years.  On the trail of the ‘free range eggs’ that started in the 1970s, many unusual eggs have appeared since then offering the consumer a wide range of eggs to choose from. They have speciality names and types and are always more expensive than nameless eggs.  As far as flavour, nutritional value and possibilities for use, there is little or no difference between them and the ‘ordinary’ egg.

Eggs from batteries
Not only the accommodation but also the feeding of battery hens involves the minimal requirements. Feeding and drinking water is carried out fully automatically.   Rearing chickens in a laying battery is certainly the cheapest way of producing eggs.

free range eggs

Animal friendly produced eggs
There are various ways of producing eggs in a more humane way.  These include:

    • Free range eggs
    • Voliere eggs
    • Eggs from hens that have some access outside
    • Eggs from hens that have access to lots of space outside, extensive system

These eggs are different from ‘ordinary’ or battery eggs since the chickens have better accommodation - they are more animal friendly.  Other egg types such as corn and grain eggs are more expensive as the chicken feeding has stricter requirements that must be met.

There are eggs that produced with a combination of better accommodation and higher quality feeding.  There is naturally a price difference for this type of egg.
Their packaging (boxes) or the stamps on the eggs themselves can identify the above egg types. 

Weight
Eggs from class A, fresh eggs are selected in eight weight categories from 0 – 7. The weight category must be stated on the box.

Weight category

Weight

0

75 grams or over

1

70 – 75 grams

2

65 – 70 grams

3

60 – 65 grams

4

55 – 60 grams

5

50 – 55 grams

6

45 – 50 grams

7

Less than 45 grams (young hen eggs)

Egg products

When purchasing egg products, distinction is made between:

    • Prepared fresh eggs such as hard boiled peeled eggs or boiled ready for peeling
    • Pasteurised or liquid egg products such as whole eggs, egg whites or egg yolks
    • Egg powder such as whole egg powder, egg yolk powder, egg white powder or omelette mix
    • Deep-freeze egg products such as egg- rolls

In bakeries and in pastry sections of large kitchens where many eggs are used, fresh eggs are often substituted for egg products.  All of these products are made from fresh chicken eggs.
It is sometimes sensible to substitute pasteurised egg products or convenience egg products for fresh eggs.  It is naturally dependent on the dishes being prepared and the customers being catered for.

2.         The physical condition

Fresh eggs

Imagine that it were possible to cut a raw egg in the shell through the middle.  From the outside to the centre, the following could be seen: the eggshell, the shell film and the air chamber, the egg white with the attachment cord  and the yolk with the egg cell.

Image:Ei1.jpg
  1. Eggshell
  2. Outer membrane
  3. Inner membrane
  4. Chalaza
  5. Exterior albumen (outer thin albumen)
  6. Middle albumen (inner thick albumen)
  7. Vitelline membrane
  8. Nucleus of pander
  9. Germinal disk (blastoderm)
  10. Yellow yolk
  11. White yolk
  12. Internal albumen
  13. Chalaza
  14. Air cell
  15. Cuticula

The eggshell.

The eggshell consists mainly of chalk that is covered with a shiny protection layer, the egg skin that protects the contents of the egg.  This protective layer is removed when the egg is washed. The eggshell has thousands of tiny pores and holes that allow air and moisture through.  When this protective layer has been removed, bacteria can very easily enter the egg.
The colour of the eggshell, white or brown in the case of chicken eggs and speckled in the case of quails’ or plovers’ eggs has nothing to do with the flavour or quality of the eggs but is dependent on the breed of the birds.

The egg white and the attachment cord( chalazas )
The egg white, that at first glance appears to be one complete part of the egg, is actually formed in three layers.  The middle layer is much thicker and gelatinous (especially with fresh eggs) than the other two layers, but the longer it is stored, the thinner this layer becomes.  This is one of the tests for egg freshness – the thinner the egg white is, the older the egg.
The attachment cords (two – one at either end of the egg) are part of the egg white. They are cords of thick egg white that hold the egg yolk in place.  The older the egg becomes, the more these cords are stretched whereby the egg yolk begins to float and can eventually end up next to the eggshell.  For this reason, older hard-boiled eggs are not suitable as garnishes.
(This is yet another test of egg freshness if the egg yolks are not in the centre of the egg).


What happens when an egg becomes old?

    1. Through the ‘breathing’ of the eggshell, the degree of the acidity is changed (pH) as the carbonic acid is expelled.
    2. The change of the degree of acidity influences the proportions of thick egg white/thin egg white.  With fresh eggs the proportion is 60/40.
    3. The difference in thick and thin egg white is very noticeable with fresh eggs. the thick egg white surrounds the almost round egg yolk.
    4. When an egg becomes older, (two to four weeks)  the proportions change.  The percentage of thick egg white decreases. The egg yolk becomes flatter as the  attachment cord is stretched and the amount of thick egg white around the yolk will be practically non-existent.

The egg yolk and the germinal disc
The egg yolk, that is thick but liquid in its raw state, is surrounded with a strong but transparent film. This film holds the yolk together and ensures that the white and yolk remain separated.
The colour of the yolk can vary from pale yellow to deep yellow-orange.  The colour has nothing to do with the flavour, the freshness or the nutritional value of the egg but is more of an indication of the amount of carotene in the chicken feed.  Carotene is a yellow – orange natural colouring that is most commonly found in plants.
In general chickens that have feeding that includes mainly corn and some grass and other green plants/vegetables that they pick at themselves, lay eggs with a deeper yellow yolk.  Chickens that have a diet of wheat, oats, barley or millet lay eggs with a paler yolk.
Hens in batteries may have colour agents added to their feed to produce this nice deep yellow colour – it is therefore important to remember that the colour of the yolks can be manipulated!
At the edge of the yolk, straight under the film, the egg cell can be found.  This is the part of the egg that would produce the young bird after fertilization.  Eggs on the market are naturally not fertilized as there are no cockerels  in the batteries!

Egg products
The physical condition of egg products are divided into various categories: pre-pared fresh products, pasteurised/liquid, powder form or cooled/deep-freeze products.

3. Quality control

Eggs are collected several times a week from the poultry farmers and taken to the so-called packing station.  They are controlled for quality,  and sorted according  to their quality and weight, then packed for transportation.  In Europe eggs are sorted into three classes:
 A, B and C.
Class A, fresh eggs are sold via wholesalers.  Eggs from classes B and C are used only for the food industry.  Quality A eggs should be completely safe to use.  Check that the eggshells are clean and free of any cracks or small holes.  Damaged eggs have a much bigger chance of carrying bacteria.
If eggs are bought directly from the farmer, there is less certainty that the eggs satisfy all the quality demands – they have not been controlled.  Defects and abnormalities such as thin shells can be more common than if they are bought via the wholesalers.  They may however be in some cases fresher and cheaper and if the farmer is reputable, it is good to know exactly where the products come from.

Quality classes

The following are the distinguishing factors of class A eggs:

    • The shells are normal, clean and undamaged
    • The air chamber depth between the film and the shell is not more than 6 mm and immobile
    • They are clear, transparent and jelly like
    • The yolk can be vaguely seen and has no definite outline
    • The egg white and the yolk have no unwanted material
    • The egg cell is not noticeably developed
    • The egg has no strange odour

Fresh eggs that are coded “extra”

These eggs of class A are fresher.  The air chamber depth should be less than 4 mm at the moment of purchase.  The box will indicate the date of packaging and the use-by-date. The other criteria are the same as above.

The distinguishing factors for the other two classes will not be further discussed, as they are never used in the kitchen as such.  They are used in industry for biscuits etc.

Control

The lawful regulations concerning eggs are set down in a number of quality regulations and statutes.  In Holland this control is carried out by the Control Agency for Poultry, Eggs and Egg Products (CPE) and the SKAL, a control agency for biological production methods that controls the production of EKO eggs.

The egg and the law

Only eggs from chickens that fall into the following categories, can the descriptions be used on the packaging:

    • Free range eggs
    • Eggs from hens that have some access outside
    • Eggs from hens that have access to lots of space outside, extensive system
    • Eggs from hens that have been kept in volières

Besides the above eggs can be identified for example as grass eggs or corn eggs.  This information should be on the box and the indication if they are free range, (where appropriate).

4.The Price

The price of eggs varies per type. Chicken eggs are the cheapest as they are mass-produced.  The more attention paid to the environment of the chickens, the more expensive they become compared to battery-produced eggs.  Eggs from birds such as pheasants or guinea fowl that are not mass-produced are normally much more expensive.

The treatment of eggs in the kitchen

Handling of fresh eggs in the kitchen can be broken down into the following sections:

  1. The transport
  2. The delivery
  3. The storage
  4. The preparation
  5. The cooking

1. The Transport

Eggs are obviously very breakable. They are therefore transported in boxes, specially designed for their safe transportation.  These boxes or trays can be easily stacked so that the eggs are virtually enclosed in the carton and therefore less susceptible to breakage.  Eggs should be transported cool.

2.  The Delivery

On delivery the eggs should be checked for damage.  Any broken eggs should be used directly or returned.

Freshness

At the moment that eggs leave the packing station and are available for sale, they are maximally 10 days old.  Egg producers are required to indicate on the boxes the date the eggs were packed.  They may be sold to maximum 21 days after laying.  Particularly fresh eggs maybe labelled as ‘extra’ (extra fresh).  However after the seventh day after packaging and the ninth day after laying, this addition information must be removed if the eggs are unsold.
It is possible to store eggs for several weeks, however since there is a danger of contamination and the use of fresh eggs is preferable, there is no point in storing eggs longer than a week or at the most two weeks.

 Note:  The freshness of an egg may be determined by placing the eggs in a large bowl of cold water, the ones that float are useable.  Another test is to break the eggs on to a plate: the truly fresh egg has a high rounded  yolk and a thick translucent white, which keeps its shape round the yolk.

3.  The storage of fresh eggs

In principle eggs can be stored for around six weeks after the packaging date.  Use of older eggs  is not advisable, as the flavour will deteriorate in this time.  Do not store more eggs than required and store them preferably cool, but not too cold 7 - 13º C. Avoid large temperature changes as condense on the eggs will facilitate bacteria entering the eggs (the outside skin will disappear due to the condense and allow easier access through the eggshell).
The best position to store eggs is the pointed side down so that the air chamber is at the top. In this position, the yolk remains better in place as the attachment cord on the stump end is a little thicker and stronger than at the pointed end.

Rule 1.  Store eggs with great care and take note of any reduction in quality

The porous eggshell allows easy access to odours.  If eggs are stored close to other products with a strong smell, for example onions or garlic, in short space of time, the eggs will absorb these flavours.  This can work to the chefs’ advantage if this is required for example by laying one or two truffles among the eggs.  The eggs absorb the truffle flavour and can be used for very tasty omelettes without actually using the truffle.

The porous shell will lose quality the older the eggs become. Moisture that is expelled out of the egg will ensure that the contents of the egg will shrink.  The contents of an old egg will slosh when shaken because the air chamber has become bigger through the evaporation of the watery part of the contents.

Freezing

Raw eggs cannot be frozen whole, however if they are separated (yolks and whites), they can be frozen separately. Egg yolks should be frozen with 6 grams of salt per 100 grams of yolk.  The salt ensures a lower point of freezing whereby smaller crystals are formed and the damage to the structure of the yolks reduced.  The egg whites require no additional ingredients and can be used when defrosted in the same way as fresh egg whites.

4. The preparation of fresh eggs

Separating eggs
Many recipes require that the eggs should be separated before use.  The yolk must be separated from the white.  This is easier to do when the eggs are at room temperature. Fresh eggs are also easier to split or separate than older eggs as the chance that the film of the yolk will break is greater causing the white and yolk to run together.  From the point of hygiene, it is advisable to use an egg separator for this purpose.  What is often done of course is the egg is moved back and forth between the two halves of the eggshell and the white runs off into a container. However, this increases the chance of bacterial contamination.

Unused egg whites can be frozen for later use or stored in the fridge for about one week in a clean, covered storage box.
Unused egg yolks can be stored two or three days in the fridge but should be covered in a layer of water or oil to avoid them drying out.
Eggs used for cakes and pastries should always be used at room temperature.

5.  Cooking fresh eggs

Rule 2:  Hygiene Rules should always be taken into consideration

Hygiene is very important when preparing and cooking fresh eggs.  Personal hygiene and the use of suitable and clean materials are of the utmost importance.

Salmonella

The Salmonella enteritidis is a bacterium that is most commonly found in animal products.  It is possible that Salmonella can be found in eggs.   Food that has been contaminated with Salmonella bacteria can cause bad stomach pains, especially in young children, old age pensioners, pregnant women and people who are ill in general.  Salmonella can cause deaths.   Luckily it does not take much effort to ensure that vulnerable people can eat eggs or dishes that include eggs, without harmful effects.
When eggs are heated to a temperature of at least 70º C, the salmonella bacteria is made harmless.  Hard-boiled eggs and dishes where egg yolks are heated sufficiently are risk free to all consumers.

The danger is mainly in dishes where raw egg yolks are used.  For example mayonnaise and dishes where egg whites are whisked such as bavarois and mousses. Chefs in old folk’s homes and hospitals are advised not to use these products unless they use pasteurised versions

The handling and use of egg products in the kitchen

Again it is convenient to differentiate between various phases:

  1. Prepared fresh eggs
  2. Pasteurised/liquid eggs
  3. Egg products in powder form including omelette mix
  4. Cooled/deep-frozen egg products

Whenever the decision is made to use convenience products, it is sensible to weigh up the advantage of time saving and easy-use against the higher price paid for the product.

1. Prepared fresh eggs

Hard-boiled, peeled, and prepared eggs is time saving in their use since they do not need to be boiled and peeled.  There is also no chance of over-cooking them and obtaining an unattractive green edge around the yolks.  These eggs are stored in a conservation liquid that is made from water with ascorbic acid.  Hard-boiled, peeled eggs can be used in salads, on rolls, sandwiches and as garnishes.

2. Pasteurised/Liquid

Liquid egg products are always pasteurised, therefore heated to a temperature that has killed most of the dangerous bacteria.  These products are sold both  ‘fresh’ and deep-frozen.  The deep frozen versions are normally used in the food industry.  In contrast to the deep-frozen products, the fresh liquid egg products are also suitable for restaurants and larger kitchens.  The smallest packaging for liquid egg yolk, egg white or whole eggs contains one kilo of egg product.  Liquid egg products can be a good alternative for fresh eggs in many situations.

The use:
Liquid egg products can be used in the same way as fresh eggs are used:

    • Liquid whole egg can be used for example for omelettes, scrambled eggs, sauces, puddings, fresh pasta and cakes
    • Liquid egg yolks can be used for mayonnaise, pastry creams, soufflés or cakes.  It can also be used to glaze pastries.
    • Liquid egg whites can be used for meringue, soufflés and glazes

The advantages:
The use of liquid, pasteurised egg products has various advantages which include:

    • It saves time, it is not necessary to ‘tick’ and separate the eggs
    • There is no waste (refuse)
    • There is no chance of breakages or spoilt eggs
    • It saves storage space

Storage:
Unopened packages can be stored for approximately four weeks at a temperature of
 2-4º C.  Opened packages must be stored in the fridge and used within 24 hours of opening. All of these liquid egg products must be used at room temperature.

  1. Egg products in powder form

Egg products in powder form are mainly used in the food industry and in bakeries. They are less suitable for use in restaurant or industrial kitchens.  Not only is the flavour less acceptable but also the fact that they have to be mixed with water (and weighed off accurately)  is less user friendly than the fresh alternatives.   The size of the packaging is also normally far too large for ordinary kitchen.

Omelette mix is also available in powder form.  It is a mix of eggs, milk or milk powder, and
flavourings and it can be used directly.   Ready to use omelette mix is hygienic and quick to use however they are normally only used in kitchens where large amounts of omelettes or scrambled eggs are made.
Omelette mix can be used for omelettes and scrambled eggs with fresh ingredients added such as fresh herbs, mushrooms, grated cheese etc.

  1. Cooled/deep frozen egg products (egg-rolls)

An egg-roll is roughly twenty centimetres long and equivalent to between eight and ten hard boiled eggs.  Egg-rolls save time, as they do not need to be cooked and peeled.  There is no waste whatsoever (no end slices) and the proportion of yolk/white is 50/50.  There are special slicers available that slice the egg-roll in one go into forty even slices.
Egg-rolls can be used in salads, sandwiches, rolls and as a garnish.