7.2: Composition and Nutrition

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Table 1 Composition of eggs by percent of weight. Traces of sugar and ash are also present.
	Composition of Eggs (%) Whole Egg		Composition of Eggs (%) Yolk		Composition of Eggs (%) White
Moisture	73.0		49.0		86.0
Protein	13.3		16.7		11.6
Lipid	11.5		31.6		0.2
Table 2 Nutritional content of a large egg
		Whole Egg		Yolk		White
Weight		50 g		17 g		33 g
Protein		6g		3g		3g
Fat		5g		5g		Trace
Cholesterol		216 mg		216 mg		0
Calcium		25 mg		2 mg		27 mg
Iron		1.0 mg		0.6 mg		Trace
Sodium		63 mg		7 mg		54 mg
Potassium		60 mg		16 mg		47 mg
Vitamin A		96 RE		99 RE		0 RE

Note: B-complex vitamins, not itemized, are well represented in eggs, as are amino acids. RE = retinol equivalent, a term used in nutritional measurement.

Worth noting is the concentration of certain food elements in different parts of the egg. Note for example that all the cholesterol is in the yolk. The yolk is relatively rich in iron and the white is high in calcium.

In practice, when separating large eggs, one estimates the weight of the white as 30 g (1 oz) and the yolk as 20 g (0.7 oz). The color of the shell, which is either a creamy white or brown, is relevant to the breed of the hen, and there is no other basic difference in the content of the egg or the shell.

The color of the yolk depends on the diet of the hens. Bakers have a preference for eggs with dark yolks. Certainly the appearance of cakes made with such eggs is richer. Tests have found that, although eggs with darker yolks tend to produce moister sponge cakes, the cakes are somewhat coarser and less tender.