SALTS
Of all salts found in the body, the most abundant and valuable is sodium chloride (NaCl), common salt; it exists in all tissues, secretions, and fluids of the body, with the exception of enamel of the teeth. The amount found in food is not always sufficient; therefore salt is used as a condiment. It assists digestion, inasmuch as it furnishes chlorine for hydrochloric acid found in gastric juice.
Common salt is obtained from evaporation of spring and sea-water, also from mines. Our supply of salt obtained by evaporation comes chiefly from Michigan and New York; mined salt from Louisiana and Kansas.
Salt is a great preservative; advantage is taken of this in salting meat and fish.
Other salts—lime, phosphorus, magnesia, potash, sulphur, and iron—are obtained in sufficient quantity from food we eat and water we drink. In young children, perfect formation of bones and teeth depends upon phosphorus and lime taken into the system; these are found in meat and fish, but abound in cereals.
STARCH (C6H10O5)
Starch is a white, glistening powder; it is largely distributed throughout the vegetable kingdom, being found most abundantly in cereals and potatoes. Being a force-producer and heat-giver it forms one of the most important foods. Alone it cannot sustain life, but must be taken in combination with foods which build and repair tissues.
Test for Starch. A weak solution of iodine added to cold cooked starch gives an intense blue color.
Starch is insoluble in cold water, and soluble to but a small extent in boiling water. Cold water separates starch-grains, boiling water causes them to swell and burst, thus forming a paste.
Starch subjected to dry heat is changed to dextrine (C6H10O5), British gum. Dextrine subjected to heat plus an acid or a ferment is changed to dextrose (C6H12O6). Dextrose occurs in ripe fruit, honey, sweet wine, and as a manufactured product. When grain is allowed to germinate for malting purposes, starch is changed to dextrine and dextrose. In fermentation, dextrose is changed to alcohol (C2H5HO) and carbon dioxide (CO2). Examples: bread making, vinegar, and distilled liquors.
Glycogen, animal starch, is found in many animal tissues and in some fungi. Examples: in liver of meat and oysters.
Raw starch is not digestible; consequently all foods containing starch should be subjected to boiling water or dry heat, and thoroughly cooked. Starch is manufactured from wheat, corn, and potatoes. Corn-starch is manufactured from Indian corn. Arrowroot, the purest form of starch, is obtained from two or three species of the Maranta plant, which grows in the West Indies and other tropical countries. Bermuda arrowroot is most highly esteemed. Tapioca is starch obtained from tuberous roots of the bitter cassava, native of South America. Sago is starch obtained from sago palms, native of India.
SUGAR (C12H22O11)
Sugar is a crystalline substance, differing from starch by its sweet taste and solubility in cold water. As food, its uses are the same as starch; all starch must be converted into sugar before it can be assimilated.
The principal kinds of sugar are: cane sugar or sucrose, grape sugar or glucose (C6H12O6), milk sugar or lactose (C12H22O11), and fruit sugar or levulose (C6H12O6).
Cane sugar is obtained from sugar cane, beets, and the palm and sugar-maple trees. Sugar cane is a grass supposed to be native to Southern Asia, but now grown throughout the tropics, a large amount coming from Cuba and Louisiana; it is the commonest of all, and in all cases the manufacture is essentially the same. The products of manufacture are: molasses, syrup, brown sugar, loaf, cut, granulated, powdered, and confectioners’ sugar. Brown sugar is cheapest, but is not so pure or sweet as white 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.