A handbook of invalid cooking

by Mary A. Boland

Starch is an abundant and easily digested form of vegetable food, but it is incapable of sustaining life. It contains none of the nitrogenous matter needed for the nutrition of the muscles, nerves, and tissues. Indeed, it is said on good authority that many an invalid has been slowly starved to death from being fed upon this material alone.

Sugar. There are many kinds of sugar, the most familiar of which is cane-sugar, or sucrose (C₁₂H₂₂O₁₁). It is obtained from the juices of various plants, for instance, sugar-cane, beet-root, the sugar-maple, and certain kinds of palms. By far the greatest amount comes from the sugar-cane. It is made by crushing the stalks of the plant (which somewhat resembles Indian corn) and extracting the sweet juice, which is then clarified and evaporated until, on cooling, crystals appear in a thick liquid; this liquid is molasses, and the grains or crystals are brown sugar. White sugar is obtained by melting this brown sugar in water, removing the impurities, and again evaporating in vacuum-pans, which are used for the purpose of boiling the liquid at a lower temperature than it could be boiled in the open air, thus avoiding the danger of burning, and otherwise preserving certain qualities of the sugar. Loaf-sugar is made by separating the crystals from the liquid by draining in molds; and granulated sugar by forcing out the syrup in a centrifugal machine. The process of making beet-root sugar is similar. Sugar from maple sap is obtained by simply evaporating away the excess of water. In the East a considerable quantity of sugar is made from the juices of certain varieties of palm, especially the date-palm. Maple-sugar and palm-sugar are generally not purified.

Sucrose dissolves readily in water. By allowing such a solution to stand undisturbed for a time until the water has disappeared, transparent crystals are obtained, known as rock candy. Again, sucrose melted at a temperature of 320° Fahr. forms, on cooling, a clear mass, called barley-sugar. Heated to 420° Fahr. dissociation of the carbon from the water of crystallization takes place, the carbon appearing in its characteristic black color. This dark brown, sweetish-bitter syrup is called caramel. On cooling it forms a solid, which may be dissolved in water, and is used to color gravies, soups, beer, and so forth.

Exp. with Sulphuric Acid. A very pretty experiment to show the separation of the water from the carbon may be made by treating a little sugar in sulphuric acid. Put a tablespoon of sugar in any vessel that will bear heat, a thin glass or stout cup. Pour over enough concentrated sulphuric acid to thoroughly moisten it, let it stand for a few minutes, when it will be seen that the mass has changed color from white to a yellowish brown. The color increases in intensity until it is perfectly black, when the whole puffs and swells up, fumes are driven off, and a mass like a cinder remains. This is charcoal, or nearly pure carbon.

The explanation is as follows: So strong is the affinity of the acid for the water that it breaks up the chemical combination between it and the carbon, unites with the water, and leaves the carbon free. So intense is the chemical change that an enormous amount of heat is evolved,—so much, in fact, that a considerable part of the water is vaporized, leaving the more or less solid charcoal. The light color noticed during the first part of the union indicates that the chemical dissociation is just beginning, and that only a small amount of carbon has been set free.

Glucose. Glucose or grape-sugar (C₆H₁₂O₆) is one of the kinds of sugar found in grapes, peaches, and other fruits. It is about two and one half times less sweet than cane-sugar. It is manufactured on a large scale from the starch of corn.

Lactose. Lactose or milk-sugar is the sugar found in the milk of the Mammalia. That of commerce comes chiefly from Switzerland, where it is made by evaporating the whey of cow's milk. For sweetening drinks for infants and for the sick, milk-sugar is said to be less liable to produce acid fermentation than cane-sugar, and also to be more easily digested.

Sugar is a valuable nutrient, being very easily digested and absorbed. Cane-sugar is converted into glucose in the process of digestion by the pancreatic juice, and after absorption it is completely utilized in the body, furnishing heat and probably energy.