Untersuchungen über den Einfluß von Keimung und Wachstum der Kartoffel sowie der mineralischen Düngung auf die Eigenschaften von Fruchtsaft und Stärke

Investigated are the growth of the potato and its properties, alkaline earth and phosphoric acid contents of potato juice and starches, and also their viscosities, in 4 different diggings in dependence upon the season and the phosphoric acid fertilizing, and finally also storage and germination of the potato. Storage and germination effect a reduction of the alkaline earth content (Ca and Mg) in the juice and an increase in the alkaline earth content in the starches, the viscosity of which decreases; the phosphoric acid content in juice and starch remains, however, constant (table 1). Phosphoric acid fertilizing accelerates growth and increases the crop yield of the potato, but not its starch content; the starch yield only gets bigger as a consequence of the higher crop yield of potatoes in the corresponding ratio by about 25% (table 2). Unlike storage and germination, the growth of the potato leads to an increase in the alkaline earth content in the juice; but there is no dependence on the phosphoric acid fertilizing (table 3). The growth of the potato tuber has a different effect on pure cell and native starches. The alkaline earth content of the pure cell starch at first increases with the growth of the potato and then remains constant. Native starches, however, show no influence by growth; in them there is also no dependence of alkaline earth content on phosphoric acid fertilizing, while the pure cell starch clearly shows smaller alkaline earth content. The phosphoric acid contents of both starches are slightly dependent on growth, however, not on phosphoric acid fertilizing (table 4). The viscosities of all starches are quickly increased by the growth of the potato and achieve maximum values at normal crop time, which greatly decrease, if the potato stays too long in the soil. Phosphoric acid fertilizing increases the viscosity of the pure cell and native starch independent of the season, but in all cases, the viscosity maximum of the pure cell starches is achieved earlier than that of the native starches, also independent of the time of harvesting (table 1‐3). The difference in pure cell and native starches, and the higher phosphoric acid contents of the native starch point out to modification of the starches by ferment processes in the cell sap, the lower viscosity to decomposition reaction, the higher phosphoric acid content to phosphorylation of the starch by the potato juice.