The investigation was conducted to clarify the process of digestive degradation, of starch granules using adult rats fed raw amylomaize V starch (amylose contents 49.'3%) and raw normal corn starch. The starch granules were collected from stomach, small intestine, cecum and large intestine, at various intervals after feeding, and their morphological changes were observed on a scanning electron microscope. Most of amylomaize starch granules from stomach remained intact and had a smooth surface, but a few with numerous shallow fissures were also recognized. The majority of granules from small intestine shortly after feeding did not suffer from enzymatic erosion, but there existed some granules covered with a few large fissures on the central part of the surface. These microscopic features displayed that the fissures were deepended and enlarged stepwise with progress of digestion. Thereafter, the damaged granules seemed to be broken down into fragments by both enzymatic and mechanical actions of small intestine. From cecum and large intestine, some amylomaize starch granules were found which received on the surface additional erosions to those from small intestine. This observation seemed to suggest that degradation of starch granules were brought about not only by pancreatic enzymes but by intestinal microbes. In the case of normal corn starch, most granules from small intestine held circular pits randomly distributed on the surface, and some of the pits reached deeply through the layers inside. With the progress of digestion, these erosion extended along the lateral of the pits to come the interior layer structure in sight. Normal corn starch granules were hardly recovered from cecum or large intestine, because of a rapid breakdown by enzymatic action. From above results, the mode of enzymatic erosion of amylomaize starch granule was substantially different from that of normal corn starch granule, and amylomaize starch granule showed to be much less susceptible to pancreatic amylase. The changes of physiochemical properties of amylomaize starch granule after incubation with the extract of rat small intestine were also examined. The modified amylomaize starch with degradation of about 30% was prepared by using the extract of rat small intestine in vitro. Some characteristics of this modified starch, such as X-ray diffraction spectrum, limit of Q-amyloysis and elution pattern of pullulanase hydrolyzate on Sephadex G-50, were unaltered from the original. Similar results were obtained in the case of modified normal corn starch with the degradation of about 60%, by the extract of rat small intestine. From this result, enzymatic degradation of amylomaize starch granule was supposed to occur uniformly at both crystalline and amorphous parts.

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A new amylase from Streptomyces griseus NA-468 was isolated and some properties were studied. The amylase was purified by means of acetone precipitation, CM-Sephadex C-50 column chromatography and Sephadex G-100 gel filtration, and a single band, which has the activity of producing maltotriose from starch was obtained on a polyacrylamide disc gel electrophoresis. The purified amylase showed maximal activity at 45°C and pH 5.6-6.0. The amylase hydrolyzed amylose completely, and produced 51% of maltotriose from waxy corn starch, though pullulan, β-cycrodextrin and waxy corn starch β-limit dextrin were not attacked. From the two-dimensional paper chromatogram of the digests of maltooligosaccharides, it was suggested that the amylase cleaved regularly the third glucosidic bonds from the nonreducing end of the substrates.

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We confirmed that starch granules of potato, Chinese yam (tubers of Dioscorea batatas), banana (fruits of Musa cavendishii), lily (bulbs of Lilium sp.), gingko (seeds of Gingko biloba), high-amylose corn, lotus (tubers of Nelumbo nucifera), chestnuts (seeds of Castanea crenata), kuzu (Japanese arrowroot, Pueraria lobata) and sweet potato were respectively in decreasing order more resistant to the action of pancreatin than were those of normal corn, wheat, rice, red corn (maize morado) and taro (roots of Colocasia antiquoruni). Although starch granules of roots and tubers were, in general, more resistant to the action of amylase than those of cereals, taro starch granules were highly susceptible and starch granules of banana, gingko and chestnuts were rather resistant to the action of pancreatin comparing with those of the normal corn. We also examined relative susceptibility to pancreatin of starch granules of 13 cultivars of legumes (Vicia faba, Pisum sativum var. arvense, Phaseolus vulgaris, Vigna sesquipedalis, Vigna angularis, and Dolichos lablab). These starch granules were, in general, less susceptible to the enzyme action than those of the normal corn. By scanning electron microscopy (SEM), damage on the surface layers of legume starch granules could not be observed after the action of pancreatin, but, step-shaped inner structures of some granules were visible. Starch contents of starchy legumes, soybeans and peanuts were 35-40, 0.8-1.4 and 5.1%(on wet weight basis), respectively. Starch granules with smooth surfaces embedded in cells of dissected cotyledon were observed by SEM of ungerminated seeds of legumes and peanuts. After 7 days of germination, although some starch granules had smooth surfaces, some other granules had rough surfaces. However, patterns of enzymatic erotion of the starch granules visible in the dissected endosperms of normal corn following the early germination period were seldom observed in the case of the cotyledon of germinating legume seeds except for those of azuki beans and peanuts.

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The objective of the present investigation is the establishment of the appropriate techniques to improve the taste qualities of rice grown in the Hokkaido area by the application of the basic knowledge in the field of starch science. Results obtained are as follows: 1) Some physical and chemical methods for evaluating the taste qualities of rice, namely, the blue value method of Juliano, texturometer measurements and Brabender amylography, were modified and applied to the Hokkaido rice. The taste qualities of the Hokkaido rice are quite different from those of the Honshu (the Mainland of Japan) rice in the criteria such as pasting characteristics, retrogradation properties and amylose contents. 2) It was essential to put the better properties of gelatinization and retrogradation in the rice cultivar adapted to the Hakkaido area to improve the taste qualities of the rice. The author proposed that the development of the rice cultivar having the lower amylose contents and adapted to the area is the immediate importance as one of the approaches for quality improvements of the Hokkaido rice. 3) Amylose contents in the Hokkaido rice are influenced by the genetic backgrounds and the environmental conditions such as temperature during ripening period and supply of fertilizers. a) Amylose contents of rice grown at 23°C during all ripening period were 3.6% lower than those at 13°C by growth-cabinet experiments. Amylose contents were also affected by temperature in the night and in the, day during the ripening period, b) The blue value method is one of the effective methods to select individual rice from mother group. Because the method has good corelations to genetic variations. c) The taste qualities of rice were significantly inferior by deficiency of either phosphorus or potassium in the paddy fields. The qualities also tended to be lowered by increasing the amounts of nitrogenous fertilizer supplied.

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Recent advances in structural studies of cyclodextrins and their inclusion complexes are reviewed with 48 references. Especially, X-ray crystallographic data are cited in detail in relation to structures in solution and binding forces of the complex.

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