Amylase and Potato Starch

A thick paste containing 720 g. of starch in 9 liters of water was treated with malt a-amylase (until the mixture was only faintly colored 

Fraction Yield in per cent Color with iodine [ Id Mol. wt. P, % Maltose, %  

It is obvious that the fractions obtained in this manner are non-homogeneous and must contain mixtures of chains of somewhat varying lengths. Fraction PDIX, which was precipitated after concentration of the mother liquor, would be expected to be rather nonhomogeneous. This fraction was examined by means of adsorption analysis by Tiselius and Hahn, and was shown to contain 19% pentasaccharide, 40% hexa-saccharide and 38% of two higher saccharides, presumably hepta- and octasaccharides. The fraction PDXIII was investigated in the same 

The a-dextrin fractions, PDV to PDXIV, are completely saccharified also by salivary amylase. The salivary amylase produces more maltose from the anomalous fractions of the a-dextrins than does 8-amylase. The reason is, as pointed out above, that these fractions are not completely dextrinized. If we assume for example, that an a-dextrin of molecular weight 3400 contains two branching points (Fig. 5) only the part A-B is 

If the a-dextrins are treated for a long time with a-amylase they are saccharified more or less completely. This saccharification corresponds to the second slow action of the enzyme on starch. In contradistinction 

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The a-amylases rapidly alter the starch in such a way that the reaction mixture is no longer colored by iodine. With malt a-amylase and potato starch this is the case when about 7% of the D-glucosidic linkages are hydrolyzed, that is, when the apparent yield of maltose is 15-20%. (The experiments were carried out with a preparation of soluble starch.)... 

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