THE EFFECT OF CA2-IONS ON THE ALPHA-AMYLOLYSIS OF GRANULAR STARCHES FROM OATS AND WAXY-MAIZE()

Granular oat starch was subjected to hydrolysis with Bacillus subtilis alpha-amylase in either calcium acetate or sodium acetate buffer and compared with the hydrolysis of waxy-maize starch granules. The enzyme was pumped through a thin layer of starch packed into a special colum n and further into an ion-exchanger that retained the enzyme but not t he dextrins solubilised from the granules. Both the amylose and the am ylopectin components of oat starch granules were attacked by the enzym e. Calcium ions increased the rate of solubilisation of the oat starch granules but not of the waxy-maize starch granules. However, the comp osition of the solubilised dextrins was clearly affected with both typ es of granules so that the molecular weight distribution of the produc ts shifted to smaller sizes in the presence of calcium. Other salts th at were tested with the oat starch granules did not affect the solubil isation rate. Scanning electron micrographs showed that the attack pat tern of alpha-amylase on oat starch is different from the attack on wa xy-maize granules. (C) 1996 Academic Press Limited