Crystallinity was measured by X-ray diffraction method and watersaturated state was determined by means of the moisture contents calculated from the crystallinity for moistened cellulose and potato starch. In the X-ray diffractograms the upper areas which were separated by the straight line joined the points of intensity at 37" and 4" (8") of diffraction angle was the relative reflection area in the crystalline and amorphous portions, and the lower area was the background of the non-relative reflection area. The upper area separated by the smooth curve joined the minimum intensity at 4" to 37" of diffraction angle corresponded to the crystalline portion and the lower area to the amorphous one. The ratio of the crystalline portion to sum of the crystalline and amorphous portions was considered to be crystallinity. Crystallinity of the air-dried and the moisture-saturated (28%) samples of cellulose were 0.68 and 0.71, resp. The crystallinity of the air-dried and water-saturated (49%) samples of potato starch were 0.24 and 0.32, resp. ~ ~~ Untersuchungen uber die Beziehung zwischen Wassersattigung und Kristallinitat mittels der Beugungs-Methode fur feuchte Kartoffelstarke. Die Kristallinitat von feuchter Cellulose und Kartoffelstarke wurde mittels der Rontgenbeugungs-Methode, und der Wassersattigungs-Zustand wurde mit Hilfe der aus den Feuchtigkeitsgehalten errechneten Kristallinitat bestimmt. In den Rontgenbeugungs-Diagrammen waren die oberen Bereiche, die durch die gerade Linie zwischen den Intensitatspunkten 3 7 und 4" (8") Beugungswinkel getrennt waren, der relative Reflexionsbereich der kristallinen und amorphen Anteiie, und der untere Bereich warder Hintergrund des nichtrelativen Reflexionsbereiches. Der obere Bereich, der durch die flache Kurve die minimale Intensitat bei 4" bis 37" Beugungswinkel abgetrennt war, entsprach dem kristallinen und der untere Bereich dem amorphen Anteil. Das Verhaltnis des kristallinen Anteils zu der Summe aus kristallinem und amorphen Anteil wurde als Kristallinitat angesehen. Die Kristallinitat der luftgetrockneten und der feuchtigkeitsgesattigten (28 YO) Celluloseproben betrug0,68 bzw. 0,71. Die Kristallinitlt der luftgetrockneten und wassergesattigten (49%) Kartoffelstarkeproben betrug 0,24 bzw. 0,32.
The relative crystallinity of various moist potato starches were measured by X‐ray diffractometer. The diffraction patterns showed to become sharp with increasing of the amount of sorption moisture. Both areas of crystallinity portion were proportionally correlated with the amount of moisture. On the assumption that crystallinity of cellulose is 70%, that of native potato starch was showed to be 24%.
The hydrolysis of potato starch by 1‐N H2SO4/30% ethanol aqueous solution at 45°C increased linearly with increasing of hydrolysis time for 14 d. The relative crystallinity of native starch showed 0.343 and 0.350 by symmetrical reflection and transmission techniques, resp. The increasing ratio of relative crystallinity to hydrolysis time corresponded very closely with that of 1/hydrolysis residue up to 14 d. These facts suggest that only the amorphous region of the starch granules will be hydrolyzed by the acid. By differential scanning calorimetry the calorimetric enthalpy of potato starch containing about 200% moisture content was found to stay largely unchanged by acid treatment for 6 d. The swelling power at 70° and 80°C of potato starch reached to the minimum value and, moreover, from the gel‐chromatogram patterns of the acid‐treated starches, the crystalline region of the starch granules may begin to deteriorate slightly by acid treatment for more than 6 d, although the relative crystallinity by the X‐ray diffraction method increased slightly with passing of hydrolysis time.
The hydrolysis of corn starch by 1N H2SO4‐30% ethanol aqueous solution at 45°C increased linearly with increasing of hydrolysis time for 20 d. The relative crystallinity of native corn starch showed 0.350 by X‐ray diffraction and it increased gradually with increasing of hydrolysis time up to 8 d. The increasing ratio of 1/hydrolysis residue to hydrolysis time increased more largely than that of relative crystallinity after 14 d. On the other hand, the relative crystallinity of native corn starch by deuteration showed 0.341 very near to the value by X‐ray diffraction. Moreover, this increasing ratio of the crystallinity accompanied by acid hydrolysis showed an inclination similar to that given by X‐ray diffraction. These facts suggest that the exchanging of OH for OD groups may be caused very a little in crystalline region of corn starch granules.
Specific volumes of starch, crystalline portion and amorphous portion are discussed and the crystallinity is calculated from the specific volume. The specific volume of starch is calculated from the density by extrapolation of the moisture content zero. The specific volumes of the amorphous portion seem to be almost the same as that of cellulose. One is 0.673 for potato, waxy corn and waxy rice and the other is 0.684 for sweet potato, tapioca, wheat and corn. The crystallinities of the starches calculated from the specific volumes with a special equation are reported.StarchlStHrke 31 (1979) Nr. 3, S. 73-75
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