Egg is one of the most nutritious foods on earth, it contains all the required vitamins and minerals required by man to live healthy. There are some parameters to be considered in determining the quality of eggs.
The quality will be determined by both the external and internal qualities of the egg.
The external qualities to be considered are:
• Shape of the egg:
Round or Long eggs are undesirable as they are not liked by commercial poultry keepers because they are difficult to pack into trays or crates and are liable to become broken.
• Shell quality:
The shell of eggs must be durable to handling. A broken egg cannot be sold. There is a strong correlation between shell strength and shell thickness. This means thickness of shell is determined by many factors including the physiology of the bird, air temperature, nutrition and disease conditions. Infectious bronchitis has a particular effect on shell development.
• Shell color:
The color of the egg shell is determined by a thin layer of ooporphyrin . the color of the shell has no effect on the nutritional quality of the egg but in several countries notably in the UK, consumers have preferred brown shelled eggs to white shelled eggs and have paid a premium for them.
The internal qualities of egg.
There is nothing more likely to put a consumer off eggs than for them to be given eggs with substandard internal quality. The internal characteristics that should be considered are as follows.
• Blood and meat spots:
Blood spots are caused by blood being released into the yolk when the follicle ruptures from the ovary. Meat spot normally come from the oviduct and are most commonly found in the albumen. Neither blood nor meat spot is harmful to the consumer but their presence is not likely to impress consumers. The predisposition to both characters is inherited and the amount of these faults can be reduced by selection of stock. Blood spots are more common in birds fed on high level of vitamin K.
• Yolk color
The color of the yolk is determined by the presence or absence of xanthophylls, some of which are not precursor of vitamin A. The color of the yolk is not a guide to to the yolk’s nutritional value since vitamin A itself is colorless. The color of the yolk is influenced to a large degree by nutrition. In fact it is possible to influence the color of the yolk to a very precise degree by the feeding of artificial pigments such as canthaxanthine.
• Proportion of thick white
Eggs containing a large proportion of thick white are normally regarded as being high quality. This is because on storage the amount of thick white decreases and thin white increases. Therefore there is a natural association between thick white and quality. Certain diseases, notably infectious bronchitis, reduce the proportion of thick white.
Stale eggs will have undesirable taints due to rotting. Eggs stored for a long time are more likely to be unsound. This can be determined by immersing the eggs in water. Those who float are more likely to be old and unsound.
Tainting may also be caused by feeding inferior quality fish meal.