This section is from the book "Mrs. Allen's Cook Book", by Mrs. Ida C. Bailey Allen. See also: The Conscious Cook: Delicious Meatless Recipes That Will Change the Way You Eat.
A slight knowledge of the composition of vegetables is of great help in their preparation. They are made up of countless little cells, each containing a semi-fluid material holding the sugar, protein, starch and salts in solution. The layer next the skin is richest in salts. Knowing this the thinking housewife will realize that vegetables must be cooked in such a way as to retain the semi-fluid material, and to keep in the salts. So she will always use boiling water, which has the property of bursting the starch grains immediately, so holding the nutriment in the vegetable; preferably she does not pare them at all, steaming them instead. As the plant grows older the cell walls harden into woody fiber, necessitating longer cooking, and as soon as the vegetables are taken from the ground the water commences to evaporate, and they become withered or shriveled, as the case may be.
To overcome this, it is necessary to put them into cold water, so that they may re-absorb the moisture, remembering that this treatment should be used only when necessary, as every minute of soaking means a proportionate loss of salts.