SynopsisX&geli-t,ype :~tnylodextriiis were prep:ired froin v:iriocis si:ircIi types: iiat,ive star& granrlles from potato, w:my miize, wt~iiikltd pe:i, :itid liigh-:itiiylose maize, and from a c*oiiiliiercial it111ylose ("Siiperlose"). 'l'hc. g r i i i i i i h st:trc-lles :iii(i t~.lrogr;ided amylose were treated with sulfuric, : i d :ii 22,"-2.i" for 13 t i i o i i 1 Ils, the ~~t~dissolved residues were washed free of acid : i t i d air dried. X-ray dilfrwtioii p i t teriis showed that, amylodextriii from w a y maize s1wrc.h (A-lype) :itid poixto st:trc.h (B-type) retain the same diffraction type as that. o f the p:iretit st:irch. 0 1 1 c o~~v e t~i o i~ of :l st:irc.h to an amylodextriii, the sharpness aiid iiit eiisity of the diIfr:~vti~~ii piteriis are either retained (waxy iryaize starch), improved (slightly wit 11 potato, signific.aiitly with high-amylose maize, atld very markedly with writikled pea) or developed (amylose). The results indicate that the crystallitie regioiis of a lint ive st.arc*h gr:itiiile, retrograded amylose, or amylodextriti are exceedingly resistant lo :ic.idir hydrolysis :it roo111 temperatiire. In contrast to the parent starches, iiittive :tiiiylodextriti.iiti little if at :ill with dilut,e iodine solution. The iodiiie stailis of dissolved :miylodext riiis were red (waxy inaize), red-pitrple (pOt,at,(J), o r purple (arnylosr, liigIi-:it~~ylose ni:tim, :I lit1 wrinkled pen).

SynopsisAlthough native B-type starch loses its sharp X-ray pattern on strong drying, the wet Nageli amylodextrin prepared from such starch gives a sharp B-pattern, that is only slightly reduced in sharpness by complete drying. Nageli amylodextrin dried admixed with a noncrystalline "filler" (e.g., starch sirup) gives an oxX-ray pattern essentially identical to that of the wet amylodextrin, except that the 16-A (No. 1) ring is greatly reduced in sharpness and intensity. Failure of the B-structure to collapse during drying indicates that water is not intercalated between turns of a helix or otherwise required to maintain the geometry and packing arrangement of the starch molecular chains. Rather, for native starch granules or amylose fibers, water relieves intercrystallite strains and consequent crystallite distortion induced by strong drying. For Nageli amylodextrin, the small molecules of starch sirup can penetrate the interstices between crystallites and prevent strain build-up during drying. For native starch granules, the interstitial regions are gel-like in character and less permeable to starch sirup molecules. A model for B-starch is proposed, that employs intertwined (double) helices.

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