Veränderungen bei der Stärke und anderen Kohlenhydraten durch thermische Einflüsse

The paper describes the changes in potato carbohydrate in the manufacture of dry products. In all types of German potatoes examined and also in the dry products made from them, sucrose, glucose and fructose were found. Xylose, which is said to cause rapid discoloration of the dry products, was not present. The content of reducing sugars varies in fresh potatoes between 1.0 and 4.7% in dry substance and in dry products between 1.7 and 2.9% in dry substance. According to American research, dry potato products should not have more than 2.7% reducing sugars with a water content of 6%. This circumstance was fulfilled in all dry products eximined, with the exception of one sample. An electrophoretic separation of the starch in its components of amylose and amylopectin was possible with borate buffer (pH = 10) and at a tension of 1900 V only if soluble starch is used, because neither potato starch nor wheat starch could be brought into solution in borate buffer. It was also not possible to separate into amylose and aminopectin‐glycolate by making a starch glycolate. On separating the starch components in an acid‐basic aluminiumoxide column, a cleavage of the higher molecular amylopectin components could be observed, in the examination of thermically treated starch of potato powder. This cleavage starts as soon as the steam treatment is in operation, in the manufacture of dry products. The average degree of polymerization of potato dry products is between 138 and 170 anhydroglucose units. For pure amylopectin starch, 2000 anhydroglycose units were found, for a corn starch with 50% amylose, 214, and for a self‐manufactured potato starch, 1250. The change in the starch and the other higher molecular carbohydrate components in the manufacture of dry products does not take place through heat effect during the drying process but as early as the steam process. The lower degree of polymerization is not only due to modification processes in the starch molecule (depolymerization of the amylopectin molecule) but to a slight extent to the fact that lower molecular polysaccharides are also involved, which are present as component of the potato substance. The amylose content of the dry products examined various between 23.0 and 29.5%. The varying amylose content is primarily caused by the use of different types of potatoes. After steaming under a pressure of ½ atm. and 1 atm., a slight reduction of amylose content is to be observed. A depolymerization of the amylopectin cannot be proved by this method.