STARCH: is one of the most important and widely diffused of the proximate principles of the vegetable kingdom, being found in nearly all plants, serving for them the purpose of reserve food. It is formed from the water, obtained by the roots from the soil, and the carbon-dioxide drawn from the air, the combination being effected by the action of the sun on the chlorophyll of the leaves and stems.
In spite of its presence in a multitude of seeds, fruits, roots, etc., frequently in large percentage and sometimes in comparatively pure state, there are only a few plants furnishing it in sufficiently large quantity and growing in sufficient abundance to be profitably utilized for its commercial production. The best known of these are Corn, Wheat, Rice and Potatoes. After them come MANIOC (which see), or Cassava, for both edible and industrial purposes, and Sago for the former only. The greater part of the American output is obtained from corn ; that of Europe from the potato.
There are two principal grades of starch, (1) that used for food and (2) that employed for manufacturing and industrial purposes. The latter may be roughly sub divided into (a) Laundry Starch, (b) starch for the finer manufacturing purposes, and (c) starch for calico manufacture, etc.
Food starches include such items as Arrowroot, Cornstarch, Sago and Tapioca (all described under their special headings).
In this country, potato starch is considered especially suitable for sizing yarns and for some kinds of silk and wool printing, but in the textile industries generally, rice and wheat starch are preferred to the potato product because of their greater stiff ening powers. Corn starch has still greater stiffening powers and is consequently the most highly esteemed for many purposes, particularly in the laundry business, because of the white, smooth, glossy finish which it gives.
Pure starch is a glistening white powder with a characteristic feeling when rubbed between the fingers. It is insoluble in alcohol, ether and cold water.
Making Starch from Corn.
The corn grain, after shelling, clearing and going through Magnetic Separators, which draw out any nails or metal fragments, is steeped in vats of warm antisepticized water for about twelve hours and is then roughly crushed in order to facilitate the separation of the hull, germ and endosperm—the last-named, the body of the corn, containing the starch, together with a certain amount of gluten, etc. In the separa
tor, the germs (which contain the oil) rise to the surface and the hulls sink. Both being removed for utilization in various forms (see table of products in the general article on CORN), the endosperms are ready for the extraction of the starch content.
First comes treatment with sulphur dioxide or a similar antiseptic, then grinding and agitating in "shakers." The resultant starch-milk is allowed to settle and the crude starch obtained passes to tanks where it is washed in, and mixed with, alka line water and is then run onto the "tables" where the starch is deposited. The tables, in numerous sections, each one hundred or more feet long, are set at a slight slope and are divided into canals, eighteen inches in width. The starch goes next to the "breakers," where it is again mixed with water, and thence to the centrifugal washers, refiners, etc., finally arriving in the muslin-lined drying boxes—constructed in sets, each box five to six feet in length and seven inches deep, with a perforated bottom. The boxes are connected with a vacuum chamber which rapidly extracts the water. The blocks thus obtained are cut into 7-inch cubes, kiln-dried and broken into various sizes.
Making Starch from Potatoes.
The potatoes are first carefully washed and put through machines which remove the stones, gravel and dirt. They are then ground by means of other machines and the resultant pulp is sieved under a continuous flow of water, which washes the greater part of the starch through, leaving a residue of fibrous matter, or pomace—which is in this country frequently discarded as of little value, the starch content being com paratively small, but in Germany is generally pressed for hog-feed.