Behavior of dextrins towards taka-diastase.

That taka-diastase, when allowed to react under the appropriate conditions, will hydrolyze starch and maltose completely or almost completely to glucose has been known for some time (2, 9). It might, therefore, be expected that dextrins, which are intermediates in the hydrolytic breakdown of starch to maltose, should be similarly susceptible to taka-diastase. Results contrary to this expectation were obtained in a series of experiments carried out by the writer. Solutions of starch, dextrins, and maltose were prepared, containing 125 mg. of the carbohydrate per 100 ml. of solution. The starch and dextrin solutions were boiled for 3 minutes before being cooled and made to volume. For the digestion 20 ml. aliquots of the solutions (containing 25 mg. of carbohydrate) were mixed in Erlenmeyer flasks with 20 ml. of thymol-saturated acetic acid-sodium acetate buffer solution, pH 4.45, and 10 ml. of dialyzed taka-diastase solution, corresponding to 50 mg. of original taka-diastase (Parke, Davis and Company, Detroit, Michigan). The flasks were tightly stoppered and incubated for 44 hours at 37-38”. Blank digests, in which the carbohydrate solution was replaced by an equal volume of distilled water, were included in all series. At the end of the digestion period the reducing power of the digests was determined by a previously described semimicromethod (8). A 20 ml. aliquot of each digest was then hydrolyzed with 1.6 ml. of 25 per cent hydrochloric acid for 1 hour in an autoclave at 15 pounds pressure. This treatment is known to result in the complete breakdown of starch and dextrins to glucose (3). The hydrolysates were cooled down, transferred to 50 ml. standard flasks, neutralized, and made to volume. The reducing power was then again determined. By expressing the reducing power after taka-diastase digestion as a percentage of the reducing power after acid hydrolysis (with the necessary corrections for blank values and dilutions) a measure of the degree of completeness of the taka-diastase digestion was obtained. The results are given in Table I. As will be seen, all the destrins proved more or less resistant to takadiastase under conditions under which starch and maltose were almost completely hydrolyzed. The degree of resistance increased with the darkness in color of the dextrins, and remarkably similar results were obtained