INTERNAL STRUCTURE OF THE POTATO STARCH GRANULE REVEALED BY CHEMICAL GELATINIZATION

Potato starch was separated into four different size groups. The starch of a uniform granular size with diameters between 30 and 52 mum was chemically gelatinized at the periphery of the granules with aqueous calcium chloride (4 m) at 23-degrees-C. Chemically gelatinized starch at the periphery was mechanically removed from the granule by using a blender. The gelatinized starch and the remaining granular starch were subjected to iodine titration, gel permeation chromatography, amylopectin branch-chain-length, and phosphorus analyses. The results showed that amylose was more concentrated at the periphery than at the core of the granule. Amylose at the core had larger molecular size than that at the periphery. Amylopectin at the core had longer long B-chains than that at the periphery. Starch phosphate esters were more concentrated at the core than at the periphery.