composition of an egg

 Egg White (Albumen)                            Yolk

 85.7% Water                                            1% Vitamins A.D.

 12.16% Protein                                       31.7%  Fat.          Water

 0.59% Minerals (Sulphur) .                   50.9% Protein     Minerals



 The egg, like the wheat grain, is the beginning of a new life and contains all the essential ingredients required for that new life to begin and is therefore a good source of nutrition for mankind.

Eggs are laid by the female of a number of different species such as birds, reptiles, amphibians and fish and have been eaten by man for many thousands of years.

The most popular egg being used today is the chicken egg. Duck, quail, fish roe, caviar are also widely used. Many types of birds eggs are widely used across the world. Before bird protection laws were introduced in the U.K. sea gull eggs were used ,especially in costal areas.( note: many schoolboys, living in costal towns, could earn pocket money or help the family budget by collecting gulls eggs to sell. With the introduction of the protection laws this practise was stopped. Today in most costal towns, gulls have now become a pest and in some cases a health risk).

Figures released in 2012 indicate that over 12,000 million eggs are consumed in the U.K. each year, that is approximately 190 eggs per capita or 4 eggs per week per person. 

Egg Sizes.

Eggs are now sold in the U.K. in four different sizes,        Small,    Medium,    Large,    Very  Large,

replacing the old system of 0-7 grading. A recipe may state the number of eggs required as apposed to the weight of egg. This can be a problem to the home baker who generally will be only making small mixtures. If the wrong size eggs are used, the whole balance of the recipe will be out and subsequently the end product will be affected. This is one area in which the home baker has to take particular care.

               New Size                          Weight                        Old Size

                      Very Large                      73g + over                      0 -1

                  Large                              63--73g                          1,2,3,              

                  Medium                          53--63g                          3,4,5,

                  Small                              53g + under                   6--7

Under European law there are two classes of egg quality  A & B  grade A being the highest grade.

The British Egg Information Service recommends using Large eggs in recipes that specify the old size 3 egg . As can be seen from the chart above it is quite possible to buy a carton of 12 Large eggs all weighing 73g or on the other hand they could all be 63g. If a recipe states 4 eggs this could lead to a difference of  40g. This represents a difference of at least 15%  extra. which will most certainly unbalance a given recipe. Whilst I appreciate this may appear as being pedantic,  it will explain why your results may vary from time to time when using the same recipe.

In a commercial situation the egg would be cracked and then weighed. A lot of recipes are written with the ingredients as % of (usually) the total flour weight. With modern digital scales it is now very easy for the home baker to weigh  ingredients, crack the eggs into a container and  lightly mix to combine the yolk and whites and place another container on the scales and press zero. Now you can pour the mixed egg into the container on the digital scales and weigh the required amount accurately  

The colour of a chicken egg depends on the breed of hen and does not effect the value of its contents.. An egg consists of an outer shell made of Calcium Carbonate and is porous, joined to the inside of this shell is a thin membrane, there is a space at the blunt end of an egg, between the shell and membrane known as the air cell/pocket, this acts as a shock absorber and also provides Oxygen for a chick if one is formed. The white of the egg consists of three layers,thin,thick and thin again. This supports the yolk in the centre when the egg is fresh. The yolk is suspended in the egg white by two strands, indicated in diagram above, as white squiggles above and below the yolk and  known as the chalaza. These also act as shock absorbers. The chalazae are often removed when making certain products to ensure a smooth texture, for example it is best to pass an egg custard through a strainer/sieve before filling and baking.

The Nutritional Value of an Egg

Eggs are very good in nutritional value, the white containing a high proportion of water, protein and minerals. The yolk is rich in protein, fats and vitamins A,D. the fat is in an emulsified state, which is easily digested. Naturally reared free range produced eggs tend to be higher in nutritional quality, with less cholesterol and fats and higher in vitamins. The content of the egg is very much dependant on what the hen eats. The egg is one of the few foods to naturally contain Vitamin D. They also contain Cholesterol, 1 large egg = 2/3rds of the daily intake but not all is absorbed by the body. 

The Function and Uses of Eggs in Baking.

Eggs enrich, flavour, moisten, shorten, help form glazes and in cake making, assist in the aeration of the product. The colour contained in the yolk gives an attractive shade to the crumb and helps to give structure to the finished product.

Whole Egg. 

Whole eggs are amongst the most important of all the bakers raw materials and are used in the production of cakes, sponges, biscuits, pastries rich fermented goods and even in some types of bread. A combination of the characteristics of whites and yolks provide all the qualities necessary to give a wide range of confectionery of good flavour, colour, texture, volume and keeping qualities.

Egg Whites. 

These are used mainly in the production of confectionery, products such as Royal Icing, Meringues, almond goods, marshmallows and rich sponge goods. Egg whites consist almost entirely of a solution of 1 part protein to 7 parts water. The solution is almost tasteless and when heated it coagulates to a white opaque solid ( E.G. an egg cracked into a hot frying pan starts of  with a liquid white which  quickly changes due to the heat, similarly an egg boiled in its shell produces a solid white. When whisked or whipped it has the power to to incorporate air to produce a light foam consisting of  millions of tiny air bubbles. This increase in volume and capacity  for retaining air explains why  egg whites are used to  maintain the aeration in meringues and other products.  N.B. As an example of this method of aeration by whisking of egg whites in making a sponge. The air bubbles trapped in the goods will expand  when baking in the oven and the protein in the egg and also in the flour will coagulate thus the volume obtained by whisking is retained in the finished product.

When whisking egg whites it is important to make sure that there is no trace of fat or oil, as this has a shortening effect and will therefore not be able to retain the air, this is very important when making meringues. Some meringue recipes will include a mild acid (lemon juice, cream of tartar) or pinch of salt. This has a strengthen effect on the protein which in turn will increase the volume and help with the retention of the air.  

Egg Yolks

These are used in in confectionery, particularly in sponges and cakes, as an enriching agent because of their high fat content and to give colour to the product. Also, due to a high protein it improves the food value of the product . They help in the formation of smaller air cells and as a result, give the goods a finer texture. Egg yolks set firmly when heated owing to the coagulation of the protein, changing from liquid to a firm solid there by helping to set the cake at its fullest volume during baking.

Storage of Eggs

Whole eggs can be tested for freshness by being put into  a bowl of water, if it is fresh it will sink to the bottom, if it is stale it will rise to the top and should be discarded. The reason for this floating or sinking is due to the air cell in the egg (see diagram of whole egg above). When an egg is fresh, its air cell is small, as each day goes by, the size of the air cell increases and it starts to act as a buoyancy bag, the bigger the air cell gets the higher the egg will float. As stated, it is advisable to discard any egg that starts to float off the bottom of the bowl.

Eggs in the U.K. are not washed/cleaned for sale, this ensures that the natural protection is retained and means that the shelf life  is good and do not necessarily have to be stored at a low temperature, unlike the U.S.A. where the eggs are washed but then have to be refrigerated. Chickens involved in U.K. egg production are inoculated against Salmonella one of  the micro-organisms responsible for for food poisoning. Eggs today in the U.K. are considered very safe to eat, provided that all the necessary procedures are carried out correctly.

Eggs should be ideally stored point down in their boxes/trays , in a cool, constant temperature. There should be a slight humidity and be stored away from strong smelling goods. All boxes on eggs purchased will inform of the Best Before date, the Class, Organic or Free Range, Country of Origin, and Farm I.D. it will also state its nutritional value.