Pertinent Problems in Starch Chemistry

It is hoped that the development of improved fractionation methods will provide fresh stimulus to starch research. There are innumerable problems which require clarification, and this survey would scarcely be complete without mention of some typical outstanding points. 

Construction of the starch granule. It is unlikely that the several fractions are haphazardly thrown together to form the granule. Three types of granule structure have been proposed (1) Location of one fraction as a surface hull-substanz, (2) alternate onion-like layers of the fractions, and (3) arrangement in radial or trichitic fashion. The orientation of the individual molecules must also be considered. 

Hydration and gelatinization. There is still no clear picture of the mechanism of granule gelatinization, despite the voluminous literature 

Retrogradation. This has been employed as an omnibus term, to cover almost any type of desolvation. Methods should be devised to evaluate retrogradation on a more exact basis. Light scattering methods may have application to indicate particle size and molecular aggregation. 

Fractionation of various starches. A wide variety of starches should be separated by Pentasol precipitation, to determine the distribution of the fractions. Comparison of the physical properties of the purified fractions from typical starches (especially corn, wheat, rice, potato, tapioca, canna, lily and arrowroot) should clarify specific differences in chemical structure. 

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