Egg is a single cell and are laid by female animal of different species such as birds, reptiles, amphibians. Eggs are eaten by human beings as a nutritional food source for thousands of years. Mostly eggs are round or oval in shape. The anatomy of egg is, it consist of shell, outer membrane, inner membrane, vitelline membrane, yolk, albumin, air cell, germinal disk and chalazae. The most commonly used eggs for food are hen’s egg. Eggs are inexpensive and widely available source of protein. It not also serve as a nutritional foo but also serve a function in different recipes.
Structure and composition of egg
During consumption of egg, we see three main parts of egg, the shell, yolk and white.
Egg shell
Eggshell is the outer covering which is hard and protect inner ingredients in the egg. Egg shell is made of calcium carbonate, magnesium carbonate, calcium phosphate, soluble and insoluble proteins. The main component of egg shell is calcium carbonate (CaCO3). It contain 95% CaCO3 and the remaining 5% are calcium phosphate, magnesium carbonate, soluble and insoluble proteins components. It is considered as waste material after using egg.
Egg white
Egg white is the second major component of the egg that surrounds the egg yolk. Main components of egg white is water and protein. Water is 88% and protein is 11%. It contains bulk of egg protein. When egg is incubated function of egg white changes and used as a growth material by chick. It contains fewer nutrients.
Egg Yolk
Another component of egg is yolk. Main components of yolk are water, proteins, fats, some minerals and vitamins. It contain 48% water, 18% proteins and the major nutritional component which is 33%. It is cholesterol and fatty acid rich.
The percent composition of egg yolk and white are shown below in table
| Nutrients | Egg White | Egg yolk |
| Water | 88.0 | 48.0 |
| Protein | 11.0 | 17.5 |
| Fat | 0.2 | 32.5 |
| Minerals | 0.8 | 2.0 |
Nutritional value
Egg is a healthy and nutritional food. Egg provide high quality proteins with essential amino acids, vitamins (such as vitamin A, vitamin D, choline and selenium) and minerals. Egg also provide cholesterol and saturated fats. Selenium act as an antioxidant which helps immune system, while vitamin A and E helps to improve night vision. Folate and riboflavin helps to transform food inti energy during digestion. It provide 70 calories and 5grams fat to our body. One large size egg provide 6 grams protein and 212 milligrams of cholesterol. It is nutrient rich food material.
| Nutrient | White | Yolk | % Total in White | % Total in Yolk |
| Protein | 3.6 g | 2.7g | 57% | 43% |
| Fat | 0.05g | 4.5g | 1% | 99% |
| Calcium | 2.3 mg | 21.9 mg | 9.5% | 90.5% |
| Magnesium | 3.6 mg | 0.85 mg | 80.8% | 19.2% |
| Iron | 0.03 mg | 0.4 mg | 6.2% | 93.8% |
| Phosphorus | 5 mg | 66.3 mg | 7% | 93% |
| Potassium | 53.8 mg | 18.5 mg | 74.4% | 25.6% |
| Sodium | 54.8 mg | 8.2 mg | 87% | 13% |
| Zinc | 0.01 mg | 0.4 mg | 0.2% | 99.8% |
| Copper | 0.008 mg | 0.013 mg | 38% | 62% |
| Manganese | 0.004 mg | 0.009 mg | 30.8% | 69.2% |
| Selenium | 6.6 mcg | 9.5 mcg | 41% | 59% |
| Thiamin | 0.01 mg | 0.03 mg | 3.2% | 96.8% |
| Riboflavin | 0.145 mg | 0.09 mg | 61.7% | 48.3% |
| Niacin | 0.035 mg | 0.004 mg | 89.7% | 9.3% |
| Pantothenic acid | 0.63 mg | 0.51 mg | 11% | 89% |
| B6 | 0.002 mg | 0.059 mg | 3.3% | 96.7% |
| Folate | 1.3 mcg | 24.8 mcg | 5% | 95% |
| B12 | 0.03 mcg | 0.331 mcg | 8.3% | 91.7% |
| Vitamin A | 0 IU | 245 IU | 0% | 100% |
| Vitamin E | 0 mg | 0.684 mg | 0% | 100% |
| Vitamin D | 0 IU | 18.3 IU | 0% | 100% |
| Vitamin K | 0 IU | 0.119 IU | 0% | 100% |
| DHA and AA | 0 | 94 mg | 0% | 100% |
| Carotenoids | 0 mcg | 21 mcg | 0% | 100% |
Does body need it on daily basis?
Our body need eggs on daily basis because it is highly nutritious food. It provide calcium, magnesium, manganese, iron, zinc, copper, essential proteins, selenium and different vitamins such as vitamin A, E, D, K, folate, B6, B12, riboflavin niacin, thiamin, pantothenic acid. It also provide fats, carotenoids and cholesterol. Most of these essential nutritional compounds are needed on daily basis for our body. Egg also increase level of high density lipoprotein (HDL). High level of HDL decrease the rate of heart diseases, stroke and many different health problems. It provide 212 milligrams of cholesterol and our body need approximately 300 milligrams of cholesterol on daily basis. It provide choline which helps to build membrane. Eggs contain lutein and zeaxanthin which is necessary for eyesight. Selenium act as an antioxidant which helps immune system. Vitamin B-12 make red blood cell and synthesize DNA. It contains vitamin D which is important for strong teeth and bones.
In a study published in 2013 in European Journal of Nutrition “30 healthy men (age of 21.7 ± 1.2 years; BMI, 23.1 ± 2.7 kg/m²) were randomized to one of three test breakfasts, on three separate occasions, separated by 1 week. The breakfasts consisted of eggs on toast, cereal (cornflakes) with milk and toast, or a croissant and orange juice. Participants showed increased satiety, less hunger and a lower desire to eat after the breakfast containing eggs relative to the cereal (p < 0.02), and croissant-based meals (p < 0.0001).
It is important to eat egg on because it’s a nutritional food and provide essential nutrients. The study also concluded that egg is important food choice at breakfast. It decreases the risk of heart diseases and diabetes.
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