FOOD SCIENCE AND PROCESSING 3 (2+1)

Lesson 17 : Eggs

Pigments

1. Shell: The color giving substances in the egg-shell are ooporphyrins, derivatives of haemoglobin give brown color and oocyanin, a product of bile formation gives bluish green color to the shell Combination of these two substances in different proportion gives different shades of color to the egg shell. The egg shell devoid of these two pigments is white in color. These genes determine shell color. The color of the shell is white in majority of the breeds. Sometime, it is in shades of brown, depending upon the breed. Color does not indicate quality or the nutritive value.


2. Egg white: Egg white contains small amounts of ovoflavin due to which a greenish tinge can be seen. The more the riboflavin in the egg white, the greener is the color.


3. Egg yolk: The color of the egg yolk varies from a pale yellow to brilliant orange depending upon the amount and type of the pigment present in the diet of the hen. The color is due to the presence of carotenoids and xanthophylls. The carotenoids can be converted into vitamin A in the body. Mostly deep coloured yolks are rich in vitamin A content. Xanthophylls are responsible for the yellow colour and are not converted to vitamin A. If the hen is fed with pure vitamin A, the yolk may be rich in vitamin A but there may not be any color.