Taste, nutritional value, availability, and the cost make egg universally popular. Due to the taste, ease, and flexibility of cooking, egg preparations are favourite among bachelors and working couples. This traditional breakfast food is also consumed in different forms though out the day. Even though eggs are of animal origin, there are appreciable numbers of "eggetariens" among the vegetarians. Some people even consider unfertilised egg as vegetarian. The eggs of hen, duck, goose, quail, turkey, and turtle are consumed. Among them hen variety is the most popular one.
Nutritive value of Egg
The egg is to provide complete food for the chick embryo unlike all most all mammals, where mother continues to provide all nutrition till birth and even after birth during early life. This requirement of nature makes egg rich in essential nutrients. The shell pigmentation of white or brown does not bear any relation to the nutritive value. Egg protein are best in quality and are taken as standard for comparing the quality of other food proteins. Egg protein is better digested, absorbed, and utilised by the body than any other source.
A hen's egg weighs about 55 to 60 gm and consists of 10% outer layer, 60% white and 30% yellow yolk. Outer shell consists of calcium carbonate, white portion is made up of protein known as egg albumin which is of high biological value. Egg contains about 11% proteins. Egg white is also a good source of riboflavin. The yolk contains mainly fat. Egg supplies fat in an emulsified form, which can be very easily digested and assimilated in the body. Egg yolk contains 1.33gm of cholesterol per 100 gms. The egg yolk is a source of vitamin A, B vitamins, calcium, phosphorous, lecithin and iron. Iron of yolk is easily digested and assimilated in the body.
An average hen's egg of 60gm consists of 7.9gms of protein, 7.9gms of fat, 103kcl, 36mgs of calcium, 132mgs of phosphorous, and 1.26mgs of iron. Egg powder contains about 49% of proteins and 43% fat and it is also a good source of vitamin A and riboflavin. It is rich in cholesterol (3.9gm per 100 gm) and is a good source of iron and phosphorous.
Soft boiled and poached eggs are better than eggs cooked in other ways. The yolk is easily digested even by infants of 9 months old. Eggs are useful in slimming diets since they have only negligible amounts of carbohydrate but plenty of protein, vitamins, and minerals.
Limiting factor of egg is that it does not contain vitamin C. Raw albumin contains an anti digestive factor that interferes with digestion. Egg also has a compound called avadin, which react with biotin (Vitamin H) and make it unavailable. Both these factors get destroyed on heating.
Eggs are the ideal nutritive food for the ill and convalescent patients. Those who suffer from gastrointestinal tract disorders, particularly in diseases of the colon eggs are the best food because of their nutritional value and lack of residue.
A common question asked to me is about the recommended number of eggs per person. There is an ambiguity about it. The British heart foundation recommends eating no more than four eggs a week. But the world health organisation how ever suggests an upper limit of ten eggs per week from all sources including mayonnaise, biscuits, cakes, mousses and sauces.
Nutritive value of eggs per 100 gm*
*Source: National Institute of Nutrition
Storage and testing of fresh egg
Fresh eggs have the best nutritive value. Eggs stored in a cool place and away from any odour stay fresh for a longer period. It must be stored with the pointed end down, so that the yolk remains centred in the egg and away from the air pocket.
The method of testing fresh eggs is to dip them in water. A rotten egg due to liberation of gases like carbon dioxide and ammonia will float while a fresh egg sink to the bottom.
Allergy and infection
Eggs or its products may be the cause of allergies in some people. It usually manifests as skin rashes or breathing difficulty. Avoid not only egg but also egg preparation such as biscuits, cakes, souffles, sauces, puddings etc. The common infection by eggs is by the salmonella group of organisms. If eggs are well cooked this danger is prevented.
Eggs may cause constipation due to low residue and easily digestibility. Include fibrous foods such as green vegetables and fruits in one`s daily diet. Patients suffering form gallbladder disorder should avoid egg yolk since the fat in yolk could cause contraction of the gall bladder resulting in pain and discomfort.