Читать книгу The Boston cooking-school cook book - Fannie Merritt Farmer - Страница 9

Table of Contents

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.