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

Wrinkled pea starch, separated into fractions containing intact granul es and fragmented granules together with small intact granules, respec tively, was hydrolysed by the alpha-amylase of Bacillus amyloliquefaci ens in a column. The solubilisation rate was similar for both fraction s and occurred in three stages; initially increasing, then slowly decr easing, and finally it was very slow. The mixtures of solubilised dext rins had DP (degree of polymerization) 2-100 and their compositions ch anged as the solubilisation proceeded through the different stages. Th e products were mostly linear and the composition of the granular resi dues indicated that amylose preferentially solubilised. Scanning elect ron microscopy could hardly reveal the site of the attack even though 20% of the granules had been solubilised. It is suggested that the enz yme attacked amylose chains in an amorphous state, whereas chain resid ues with DP 50-300 remained in the crystalline parts within the granul es.