A MEDIUM-sized egg has an energy value of 78 kilocalories (324 kilojoules) and the consumption of one egg a day would contribute only around three per cent of the average energy requirement of an adult man, and four per cent of an adult woman.

Eggs are a good source of essential minerals such as calcium, iron, phosphorus, zinc and iodine. Although eggs will remain safe to eat for around 28 days, the internal quality begins to deteriorate from the day they are laid. Newer eggs have firm whites that hold their shape. Poor quality whites usually indicate the egg has been laid for longer than you realise.

On occasion, you will find faults with your eggs, and it is useful to know the causes. Not all problems can be prevented but it is helpful to know the reason for problems in your table eggs.

The yolk colour of eggs naturally varies from light yellow to a deep-orange yellow, depending on what the hens are eating. Sometimes, free-ranging hens will produce eggs with green yolks, most frequently in the spring when plants are most lush.

Usually, shell membranes that lie just under the shell protect the egg from microbial and fungal infection. If this layer is damaged or malformed and they get into the egg, rot in patches or whole will occur. If, however, the inner membrane is damaged, the result can be bubbles in the white.

Small red to reddish-brown spots can be found in or around the yolk. They are usually caused by one of the tiny blood vessels in the ovary breaking at the time when the yolk is released.

Often people mistakenly think they indicate a fertile egg and it is the start of chick-forming. High levels of activity or disturbance, particularly at the time of ovulation, are likely to increase the incidence of these blood spots.

Meat spots are usually brown in colour, darker than blood spots, and they are found in the egg white (albumen) rather than the yolk. They consist of small pieces of body tissue, such as the internal wall of the oviduct. Their incidence varies according to the bird’s age and health, and also due to breed differences.

Some newly-laid eggs from older birds may have poor quality whites and viral disease can also cause the hen to lay eggs with poor quality whites.

TASRA ANJUM Lahore