1Vlaize-statch.—Ths grain of tho maize or Indian corn plant (Zea Mays) contains a largo proportion of staroh, the average quantity being about 53i per cent. in flat yellow American maize, and 54i ill the flat white and round yellow varieties. In ita oceurrenco and association, the atarch of the maize closely resembles that of wheat ; it differs in that the accompanying gluten forms a less tough mass, and rnay be separated without having recourse to fermentation, thus affording a bye-product of greator value for cattle-feeding purposes. The grain is cleaned, soaked in water for 24-30 hours, erushed in a roller-ruill or ground to paste between millstones, and washed iu cyliuder-sieves as described for potato-starch (see Fig. 1287, p. 1825). The starch-milk thus separated is poured upon inclined tables where the starch granules are deposited, while the nitrogenous niatters pass on to capacious tanks, and gradually subside, t,o be subsequently collected and mixed with the hulls for cattle-food. Tho starch which settles in the inclined tables forms a good paste for finishing textiles, without further treatment. Tho quality may be improved by the application of alkaline solutions, which dissolve tho remaining gluten.
There aro several modified methods of manufacturing maize-starch. Watts steeps the maize at a temperature of 25°-60° (77°-140° F.) until slight fermentation has set in. Leconte soaks the grain in a eaustio soda solution, washes it in a wire sieve, and crushes it between millstones on whioh plays a jet of wator. The stareh-milk is filtered on to the inclined tables.
Tho finer qualities of maize-starch aro largely used as a substitute for arrowroot and for making biscuits, while the lower grades serve for laundry purposes. The most extensive factories where it is produced are Brown and Polson's in Scotland, Erkenbrecher's in Cincinnati, and the Glen Cove Co. in New York ; it is also made in Brazil, New South Wales, France, and Hungary on a cousidet able scale.
Plantain-starch.—This starch, sometimes called Guiana arrowroot or plantain-meal, is extracted from the unripe fruit-pulp of Musa paradisaica, by slicing, sun-drying, powdering, sifting, and washing with water. The article is mostly exported as meal to Europe, and the starch is manufactured after arrival. The flour is said to eontain 66 per cent. of starch.
Potato-starch (Fa., Fecule de Pomme-de-terre; GER., Kartoffelstii rke).—The potato (Solanum tuberostsm [esculentump contains starch to the extent of 15-25 per cent.; the amount varies according to the soil, climate, manuring, and storage—freezing and sprouting being alike detrimental. About 66-75 per eent. of the contents are obtained by the manufacturer.
There are chiefly two methods of tnanufacturing potato-starch. According to the older and commoner plan, the potatoes are first cleaned and then grated. The cleaning embraces the washing
away of the attached dirt, and the elimination of stones and other foreign bodies. Many machines have been devised for the purpose, one of the best being Venuleth's, shown in Fig. 1282. It consists essentially of an iron receptacle a for the dirty potatoes, a shaft b carrying wooden beaters c, which revolve in a trough of water, provided with an iron grating which allows the dirty water to escape into a lower trough d, whence it can be withdrawn at the door e. The washed potatoes pass into the box f, ready to be conveyed by tbe elevators g, into the grating-machine, which usually stands on the floor above.
Another form of washing apparatus is shown in Fig. 1283, and is known as Champonn,ois'. It consists of a wooden tank a filled with water, in which revolves a cylinder b, formed of open wood work. The potatoes are fed by the hopper c, washed by the rotation of the cylinder, and thrown by the lips d upon the external inclined plane e, also formed of laths.
The grating or grinding of the washed potatoes ruptures their cells, and liberates the starch to a greater or less degree. Of the numerous graters in use, one of the best is Champonnois', shown in Fig. 1284.
The potatoes are introduced by the hopper a, aud are forced by the rapid rotation of the fliers b (800-1000 rev. a minute) ag,ainst the short saw-like teeth of the raspers c. Water is at the same time injected at d; e f are the fast and loose pulleys, and a fly wheel is fixed on the end of the shaft g. The motion of the machine is reversed every 6 hours to equalize the wear, still the raspers require sharpening after 48 hours' use. The whole interior needs frequent washing out with clean cold water, and the raspings should be removed at very short intervals.
The grated paste next requires treatment to separate the starch granules from the cellular and fibrous matters. This is effected by sifting-machines of various kinds with the aid of water. One of the simplest forms is shown in Fig.
1285 ; the brushes b rotate over the surface of the wire or hair sieve, while water is supplied by the pipes a ; motion is given by the pulley c and bevel-wheels d.
Siemens' bolting-sieve is shown in Fig. 1286. The grating-cylinder c is secured to a simple wooden frame e ; the paste falls from the oylinder upon the bolting-sieve h, supported from the frame by bars f. Tbe grating-cylinderis driven by a pulley, and trans mits motion to the pulley d, which connects with the sieve by the bar g. The sifted paste is con ducted by k to the re ceptacle /. Water is admitted to the cylinder at a, and to the sieve at i, while b is the feed hopper. The liberated starch is conducted into settling-tanks.