While buying an eatable the first prerequisite for all of us is its quality. We can gauge the quality of vegetables and fruits by looking at them, packed goods carry best before dates but eggs…. It is really a question difficult to answer. Although there are lots of industrial measures by which eggs are graded on their quality which might help us in choosing superior quality eggs.
Candling: The quality of the egg in the shell is evaluated by candling. The egg is held against a source of strong light. Candling can reveal: a crack in the shell, the freshness, the firmness of egg whitealbumin, the position and mobility of yolk and the possible presence of foreign substances like blood spots, moulds and developing embryo. As the eggs deteriorate, the chalaza weakens and the yolk tends to settle toward the shell rather than remain suspended in the firm white. Under such circumstances the yolk is more fully visible when the egg is candled. Dark yolks cast a more distinct shadow than light coloured yolks.
Floating in water: If the egg sinks it is considered as good. Poor quality eggs float due to increase in size of the air cell and due to loss of moisture. To test the freshness of an egg, plunge it into a 12 per cent solution of salted water : A fresh egg falls at once to the bottom; An egg 2 days old floats midway; An egg 4 days old rises to the surface; A 2-week old egg floats on top.
In India eggs are graded according to their weight into 4 grades. Extra large-more than 60 g, large- 53-59 g, medium- 45-52 g, small- 38-42 g. Clean eggs with unbroken shell are graded on quality depending upon depth of the air cell. Centering of the yolk and free from defects are given grade A and B in India.
So now when you go egg shopping you can look for these markers of quality assurance.