Cereal Chem 68:86-91   |  VIEW ARTICLE

Enzyme-Resistant Starch. III. X-Ray Diffraction of Autoclaved Amylomaize VII Starch and Enzyme-Resistant Starch Residues.

D. Sievert, Z. Czuchajowska, and Y. Pomeranz. Copyright 1991 by the American Association of Cereal Chemists, Inc. 

X-ray diffraction was used to follow the development of crystallinity in amylomaize VII starch samples after repeated cycles of autoclaving and cooling. Changes in crystallinity were revealed by the development of reflections at 0.529 and 0.398 nm. Reduced intensities of a peak at 0.449 nm, which likely reflected the V pattern of complexed amylose, suggested that amylose-lipid complexes melted out during repeated autoclaving and cooling. Diffractograms of enzyme-resistant starch (RS) residues, isolated from amylomaize starch samples by treatment with Termamyl and amyloglucosidase, displayed single peaks at 1.662 and broad diffraction lines at 0.537 and 0.398 nm. The patterns suggested that chain fragments, packed in a B-type crystalline structure with a slightly enlarged crystal lattice, contribute to formation of RS from amylomaize starch. Structures resistant to enzymatic hydrolysis, assessed by X-ray and differential scanning calorimetry measurements, differed in crystallinity and resistance to thermal dissociation depending on the treatment of amylomaize starch. Differences in association between the chain fragments, presumably originating from amylose and varying proportions of interspersed, less-ordered segments, were assumed to account for these findings. Conditions applied for preparation of RS, such as type of amylolytic enzyme used in the isolation procedure, also affected thermal and crystallographic properties of RS.