MICROSCOPY OF STARCH - EVIDENCE OF A NEW LEVEL OF GRANULE ORGANIZATION

Considerable information on starch granule structure may be gathered f rom a review of published data. Evidence from a range of different (pr edominantly microscopic) techniques is compared and discussed, allowin g the presence of a level of starch granule organization between that of the amylopectin lamellae and the large 'growth rings' to be deduced . This structural level of the granule involves the organization of th e amylopectin lamellae into effectively spherical 'blocklets' which ra nge in diameter from 20 to 500 nm depending on starch botanical type a nd their location in the granule. The presence of short, radial 'chann els' of amorphous material within starch granules from some starch var ieties is confirmed. The organization and structure of the crystalline and amorphous amylopectin lamellae is also discussed. Consideration o f the information regarding starch granule structure and organization to date has significant implications on the internal architecture of t he starch granule, and it is evident that the presence of the blockets and amorphous channels play a role in both the resistance of starch t o enzymic attack and the structure of the semicrystalline shells. (C) 1997 Elsevier Science Ltd.