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Determination of Total Available Carbohydrates in Forage Legume Roots by Extraction with Takadiastase, Amyloglucosidase, or Sulfuric Acid¹

Takadiastase ("Clarase 900"), amyloglucosidase ("Diazyme 160"), and a combination of the two enzymes were compared with and without acid hydrolysis of the filtrates for the ability to extract sucrose and starch and convert them to reducing sugars in the determination of total available carbohydrates (TAC). Sucrose, soluble starch, and alfalfa root samples varying in TAG content and ratio of sucrose to starch were used as substrates. Comparisons also were made between TAC values obtained by the enzyme combination and by O.2N H₂SO₄. Clarase 900 recovered significantly more sucrose but significantly less starch than did Diazyme 160 or the enzyme combination. A mild acid hydrolysis subsequent to the enzyme stage enhanced sucrose recovery but not starch recovery.

When used on the root material without acid hydrolysis, the Clarase 900 and the enzyme combination gave similar TAC values. Diazyme 160 values were significantly lower than the other two treatments. Acid hydrolysis of the enzyme filtrate increased the TAC values of most of the root samples.

The enzyme combination method gave TAC values up to three-fold higher than the 0.2N H₂SO₄ method when legume root samples were high in starch content, but the acid method gave higher values when TAC were low.

Key Words: Acid hydrolysis • Starch • Sucrose

² Project Associate (now Assistant Professor, Department of Plant and Earth Science, Wisconsin State University, River Falls, Wisconsin 54022) and Professor of Agronomy, Iowa State University.

Received for publication January 28, 1969.