This section is from the book "Mrs. Rorer's Diet For The Sick", by Sarah Tyson Rorer. Also available from Amazon: Mrs. Rorer's Diet For The Sick.
Vegetables are divided into four classes: those rich in nitrogen - muscle and tissue-building foods; those containing carbohydrates - sugars and starch; fatty vegetables - nuts and olives; and succulent vegetables, containing little but water and mineral matter.
In the first class we have old peas, beans and lentils, soy beans and the chick pea of the East. Starch is also found in goodly quantities in these vegetables. Cereals and cereal foods, as bread and Italian pastes, contain both nitrogen and starch.
In the second class, carbohydrates, we have rice, potatoes, yams, taro, cush-cush, cassava, tapioca and sago.
In the third class, vegetables containing mineral matter and water, are cabbage, carrots, turnips, spinach, cress, cymlins, cucumbers, lettuce, tomatoes, very young green peas, string beans, onions and christophines.
Vegetables as a rule should be cooked in water, in an uncovered vessel. Rapid boiling frequently toughens the fibre of underground vegetables. Cooked at 210o Fahr. they become tender quickly, and retain their flavor and color. Rice and macaroni, however, should be boiled rapidly, not that the water is hotter, but the motion of rapidly-boiling water washes apart and separates the particles. All starchy vegetables must be cooked at the boiling point.
All vegetables must go over the fire in boiling water. To green vegetables add a teaspoonful of salt to each half gallon of water in which they are to be boiled. Underground vegetables, the roots and tubers of plants, are better cooked in unsalted water. For instance, turnips are white, sweet, palatable and easily digested if cut into blocks and cooked carefully in unsalted water. If boiled rapidly in salted water, they lose their color, flavor and digestibility, and are coarse and unpalatable. Raw cabbage with French dressing is digested by a person in health in two and a half hours; boiled it takes five hours.
Dried vegetables, as peas, beans and lentils, must be cooked in soft water, if possible. The salts of lime in hard water coagulate the casein and render it dense and difficult of digestion.
For the sick, all vegetables must be freshly gathered, otherwise do not use them. They should be thrown in cold water the moment they come from the market. Do not add salt to the water as it draws out the juices and hardens the fibre.
For the convenience of persons who are on restricted diet, the vegetables in this book have been arranged in groups, so that their chemical constitutents may be seen at a glance.