STARCHES
The starches are by far the most abundant of all elements in human food. They enter largely into the composition of nearly all plants and seeds. Under the influence of the sunlight, the green-colored plants gather up the CO2 of the air and, with the water absorbed from the ground, build up starch. The plant takes all the carbon from which starch is made from the air, but while the atmosphere contains almost eighty per cent of nitrogen, the plant is unable to use it; it must secure its nitrogen from the decaying refuse of the soil. Thus the plant utilizes the waste products found in air and earth in the building of its food substances.
Starch exists in the form of small granules. Since each little starch granule is surrounded by a woody envelope of cellulose, it becomes necessary to cook all starches thoroughly in order to burst this cellulose envelope and thus enable the saliva to begin, and other secretions to continue, the work of digestion.