Enzymically Induced Changes in the Turbidity of Starch Solutions*

The usual methods for detecting the action of amylolytic enzymes on starch are confined to three types of measurements: (1) increase in reducing action; (2) decrease in viscosity; and (3) decrease in the color of the resulting dextrin-iodine complex. Optical methods based upon the changes in optical rotation (1) and upon the refractive indices of the individual split-products (2) have been less frequently employed. Yet one of the most characteristic properties of starch solutions is the fairly intense Tyndall effect they exhibit, especially some time after their preparations. This opalescence can be ascribed to the light-scattering effect of the high molecular constituents of the substrate, the amylopectin moiety probably contributing a major portion. When amylolytic enzymes are added to such solutions, certain well defined changes in the opalescence or turbidity are observed. As will be shown in this paper, each type of amylase used gives a characteristic turbidity pattern. A display of these patterns, as well as some of the pertinent, factors affecting the turbidity changes, is presented.