Page:The Boston cooking-school cook book (1910).djvu/29

 grades; powdered and confectioners' sugars are fine grades, pulverized, and, although seeming less sweet to the taste, are equally pure. Confectioners' sugar when applied to the tongue will dissolve at once; powdered sugar is a little granular.

Cane sugar when added to fruits, and allowed to cook for some time, changes to grape sugar, losing one-third of its sweetness; therefore the reason for adding it when fruit is nearly cooked. Cane sugar is of great preservative value, hence its use in preserving fruits and milk; also, for the preparation of syrups.

Three changes take place in the cooking of sugar: first, barley sugar; second, caramel; third, carbon.

Grape sugar is found in honey and all sweet fruits. It appears on the outside of dried fruits, such as raisins, dates, etc., and is only two-thirds as sweet as cane sugar. As a manufactured product it is obtained from the starch of corn.

Milk sugar is obtained from the milk of mammalia, but unlike cane sugar does not ferment.

Fruit sugar is obtained from sweet fruits, and is sold as diabetin, is sweeter than cane sugar, and is principally used by diabetic patients.

GUM, PECTOSE, AND CELLULOSE

These compounds found in food are closely allied to the carbohydrates, but are neither starchy, saccharine, nor oily. Gum exists in the juices of almost all plants, coming from the stems, branches, and fruits. Examples: gum arabic, gum tragacanth, and mucilage. Pectose exists in the fleshy pulp of unripe fruit; during the process of ripening it changes to pectin; by cooking, pectin is changed to pectosic acid, and by longer cooking to pectic acid. Pectosic acid is jelly-like when cold; pectic acid is jelly-like when hot or cold. Cellulose constitutes the cell-walls of vegetable life; in very young vegetables it is possible that it can be acted upon by the digestive ferments; in older vegetables it becomes woody and completely indigestible.