Potato Starch.
—In this country potato starch is manufactured chiefly in Maine, Wisconsin, and Colorado. The factories are of a very primitive type, the machinery consisting of a rasper constructed usually by wrapping a wooden cylinder with sheet-iron punctured so that the ragged edges of the hole are on the exterior surface as shown in [Fig. 41]. Water is added at the time of rasping, and the starch pulp goes onto gauze shaking tables where the starch grains are washed through the sieve, as indicated in [Figs. 42] and [43]. The separated starch and water go into settling tanks. Where the starch has settled into a firm mass it is broken up and sent to the drying kiln. Potato starch is highly prized as a sizing in the textile industry.
Fig. 41.—Rasping Cylinder for Making Starch.—(Courtesy Department of Agriculture.)
Fig. 42.—Shaking Table for Separating the Starch From the Pulped Potato.—(Courtesy Department of Agriculture.)
Use of the Potato in the Manufacture of Spirits.
—A much more important technical use of the potato is in the manufacture of distilled spirits. Distilled spirits made from the potato are not generally used for potable purposes but are devoted to industrial uses. In the United States, very little if any distilled spirits are made from the potato. In Europe, however, especially in Germany, the industry is one of great magnitude. Practically all of the industrial spirits used in Germany and in many parts of Europe are made from the potato. The process is a simple one. The pulp of the potato, or starch, separated therefrom is subjected to the action of malt or other diastatic action for the purpose of converting the starch into sugar. In some cases this conversion takes place by more strictly chemical means, namely, by heating the pulpy matter or the starch separated therefrom in a proper state of dilution, in contact with an acid at a high temperature and pressure. Hydrochloric acid or sulfuric acid is usually employed for this purpose. The action of the acid converts the starch into fermentable sugar, namely, dextrose, a form of sugar differing in its quality and character from that produced by malt known as maltose. Both sugars, however, are fermentable to the same degree and produce, for equal quantities of sugar, the same quantity of alcohol. When the starch is converted into sugar by one or the other of these methods it is subjected to fermentation by an appropriate quantity of yeast which is of the same family as that used in the alcoholic fermentation of other saccharine products.
Fig. 43.—The Potato Rasping Cylinder Arranged for work.—(Courtesy Department of Agriculture.)