STUDIES ON THE STRUCTURE OF PEA STARCHES .1. INITIAL-STAGES IN ALPHA-AMYLOLYSIS OF GRANULAR SMOOTH PEA STARCH

A diluted solution of Bacillus amyloliquefaciens alpha-amylase was pumped through a layer of smooth pea starch granules in a column and further into a bed of ion-exchanger that retained the enzyme but not the solubilised dextrins. The design of the experiment prevented a secondary hydrolysis of the originally solubilised dextrins. The granules were quite resistant to hydrolysis and collected dextrins from the initial stages of the solubilisation of both large and small granules had d.p. (degree of polymerization) 2-100. Large granules that were treated with a more concentrated enzyme solution in a test-tube, were solubilised up to 7%. The granular residues contained increased amounts of dextrins in the d.p.-range 50-300. Scanning electron microscopy revealed an extensive fragmentation of the granules and the enzyme had preferentially attacked the starch in layers between the ''growth rings.''