Eggs

What is an egg?
‘Eggs’ means eggs in shell, other than broken, incubated or cooked eggs, that are produced by hens of the species Gallus gallus and are fit for direct human consumption or for the preparation of egg products while ‘broken eggs’ means eggs showing breaks of both the shell and the membranes, resulting in the exposure of their contents;


The composition of eggs…
The egg weights around 60g and consists of four distinct parts. These parts are the yolk (ovum), the white (albumen), the inner and outer shell membranes that keep the white together and the outer cover of eggs. The egg white has a thick and a thin layer and the chalazae. The chalazae are twisted strands of thickened protein that are arranged in order to hold the yolk in its central position within the egg. The colour of the eggs can be white and brown. However it is possible that the brown colour of eggs has different intensities while we can find blue, rose and green eggs. The colour of the eggs depends on the hen’s breed. The outer cover shell consists of about 97% calcium carbonate and the remaining 3%, is mostly protein that has an effect on its structure.

The outer shell of eggs

The egg without its  outside shell

Putting pressure to an egg without its outside shell

a frozen egg cut in the middle-crosscut

The code of an egg

The eggs are a very important part of our diet because we consume them frequently. What an egg can offer us as food in our diet?  The edible portion of the egg, i.e. the white and the yolk, has different chemical compositions. All of the fat and the fat-soluble vitamins are contained in the yolk, while the white is composed of a large amount of water and protein. The white contains practically no fat. The eggs contain all the known vitamins but no Vitamin C. The eggs consist of the outer shell cover which is 9% of the total weight: 62% of the total egg weight is the white and 29% of it is the yolk. It is noted that the yolk contain approximately 16.5% protein as part of its weight while the albumen contains around 11% protein as part of its weight. 

 The egg is a functional food and is used as an emulsifier, a binding agent or stabilizer and many other uses in the food industry. In addition, the protein in raw eggs is only 51% bioavailable, whereas that of a cooked egg is nearer 91% bioavailable, meaning the protein of cooked eggs is nearly twice as absorbable as the protein from raw eggs

The quality of eggs…

  The European Union has set a series of Legislation that concerns the quality of eggs. The egg quality involves functional, aesthetic and microbiological properties of the egg yolk and albumen. Eggs must be stored in cool rooms at a temperature of 10 °C. A consumer should preserve his eggs in the fridge after their purchase. The main parameters that affect egg quality are diseases, egg age, temperature, humidity, handling, and storage. Other important quality characteristics are texture, color, shape, soundness and cleanliness. The shell of each egg should be smooth, clean and free of cracks. The eggs should be uniform in color, size and shape. The ‘sell-by date’ means the maximum time limit for delivery of the egg to the final consumer.

The producer code’ means the distinguishing number of the production site. Eggs are classified in categories A or B according to their quality. The eggs of class A must meet the following quality characteristics:

1. --The shell and cuticle of an egg must be of  normal shape, clean and undamaged; 
2. -- The air space of an egg must have a height not exceeding 6 mm, stationary; however, for eggs to be marketed as ‘extra’, it may not exceed 4 mm;
3. --The yolk must be visible on candling as a shadow only, without clearly discernible outline, slightly mobile upon turning the egg, and returning to a central position;
4. --The white must be  clear and  translucent;
5. --The presence of germ must have an  imperceptible development;
6. --Foreign matter and foreign smell are not permissible;

Class B eggs shall be eggs which do not meet the quality characteristics of class A above.

Class A eggs are graded by weight as follows:

1. --XL — very large: weight ≥ 73 g;
2. --L — large: weight ≥ 63 g and < 73 g;
3. -- M — medium: weight ≥ 53 g and < 63 g;
4. --S — small: weight < 53 g.

The weight-grading shall be indicated by the corresponding letters or terms or by a combination of both, which may be supplemented by the corresponding weight ranges. When Class A eggs of different sizes are packed together in the same pack, the minimum net weight of the eggs shall be given in grams and the indication ‘Eggs of different sizes’ shall appear on the packaging. The packaging of eggs class A must display visibly and legibly the packing centre code, the quality grading, the weight grading, the date of minimum durability, the farming method (for example organic , conventional or other). The packaging of eggs class B must display visibly the packing centre code, the quality grading and the packing date. The words “extra” or “ extra fresh” may appear as an additional quality indication when eggs are packed until the ninth day of laying the eggs by hens. The date of minimum durability is fixed at no more than 28 days after laying the eggs by hens.

 

 

 

Eggs different parts of its structure 

 

1. Eggshell
2. Outer membrane
3. Inner membrane
4. Chalazae
5. Exterior albumen
6. Middle albumen
7. Vitelline membrane
8. Nucleus of pander
9. Germinal disc
10. Yellow yolk
11. White yolk
12. Internal albumen
13. Chalazae
14. Air cell
15.Cuticula