STUDIES ON THE STRUCTURE OF PEA STARCHES .2. - ALPHA-AMYLOLYSIS OF GRANULAR WRINKLED PEA STARCH

Wrinkled pea starch, separated into fractions containing intact granules and fragmented granules together with small intact granules, respectively, was hydrolysed by the alpha-amylase of Bacillus amyloliquefaciens in a column. The solubilisation rate was similar for both fractions and occurred in three stages; initially increasing, then slowly decreasing, and finally it was very slow. The mixtures of solubilised dextrins had DP (degree of polymerization) 2-100 and their compositions changed as the solubilisation proceeded through the different stages. The products were mostly linear and the composition of the granular residues indicated that amylose preferentially solubilised. Scanning electron microscopy could hardly reveal the site of the attack even though 20% of the granules had been solubilised. It is suggested that the enzyme attacked amylose chains in an amorphous state, whereas chain residues with DP 50-300 remained in the crystalline parts within the granules.