Flour and endosperm starch prepared from rice grains of three Japanese rice cultivars milled from 90 to 30% of their original weight were subjected to physicochemical/structural analysis in order to examine the relationship between milling ratio and physicochemical/starch structural properties. The peak viscosity of the rice flours was found to increase with decreasing milling ratio, while that of the purified starches did not change significantly. The gelatinization peak temperature of the rice flours was found to decrease while enthalpy changes increased with decreasing milling ratio. The gelatinization peak temperature of the purified starches was not found to change significantly with different milling ratios. Differences in structural properties of purified starches were examined by gel-filtration chromatography of isoamylase debranched starch. The FI (percentage of amylose) and FIIb/FIIa (ratio of short-to-long chain amylopectin) were found to be constant for all three cultivars for milling ratios ranging from brown rice to 30%.

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To clarify the cooking and processing properties of foxtail millet flour, effects of additives on the physical properties of foxtail millet flour were studied. Four additives, sugar, salt, oil and milk, were added to foxtail millet flour, and the mixtures were measured for their viscosity and gel texture by a Rapid Visco Analyzer and a Tensipresser, respectively. The results were compared with Japanese barnyard millet, rice and wheat flour. Furthermore, foxtail millet flour was partially substituted for two kinds of wheat flour, and their mixing properties, viscosity and gel texture were examined. The pasting curve of foxtail millet flour was similar to that of the wheat flours. The gel texture of foxtail millet flour was low in firmness and adhesiveness. The firmness of the gel was twice as high as that of the control when 0.5% salt was added to foxtail millet flour, and it was 6 times higher when oil was added. The firmness of the gel was the highest when milk was added to the foxtail millet flour and it was increased more by adding milk, salt and oil together. Thus, foxtail millet flour could be used for cream croquettes because food made with foxtail millet flour was easy to shape. The dough texture of hard wheat flour measured by Farinograph did not show a significant change when replacing 10% of hard wheat flour with foxtail millet flour. According to the expansion of volume and sensory evaluation, foxtail millet flour could be substituted for 10% of hard wheat flour and used for bread.

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Two isolation methods, the Matsunaga et al. method and the improved Matsunaga method, were compared for the purpose of isolating high quality foxtail millet starch in a short period of time. Using the improved Matsunaga method, the foxtail millet starch was washed and sedimentated repeatedly after neutralization of sodium hydroxide by hydrochloric acid. The starch isolated by the improved method was high in yield, and low in protein and ash content. Thus, with the improved method, high quality foxtail millet starch was able to be prepared in 7 days. The starch isolated contained 18.5% amylose, showed X-ray diffraction pattern A, had an average diameter of 9.3-11.0 μm, larger than the average diameter of Japanese barnyard millet starch, and showed a polygonal shape like Japanese barnyard millet starch. The pasting curve was similar to that of corn starch. We thought foxtail millet starch could be used effectively in the same way as corn starch, because the results of DSC showed that foxtail millet starch retrogrades faster than rice or wheat starch.

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Effect of the heat-moisture treatment of glutinous rice on the gelatinization temperature, the color tone of rice, and promotion of the hardness of mochi-kiji were studied. Heat-moisture treatment was carried out under both the limited moisture condition (the sealing system) and 100% relative humidity condition (the open system), using Hakuchomochi from Hokkaido, adjusting to 15.2 and 20.3% of moisture content of rice. By means of the heat-moisture treatment, the gelatinization temperature of glutinous rice shifted to the high temperature, and the hardness of mochi-kiji increased. The movement to the high temperature was affected by the method of the heat-moisture treatment, the heating temperature, the heating time, and the moisture content of rice before the treatment. It was recognized that a closed relationship existed between the effective accumulative temperature [[heating temperature - 80°C]×heating time (h)] and the gelatinization temperature. The gelatinization temperature of the heat-moisture treated rice showed an almost fixed value, when the total effective temperature was 120 (°C·h) in the sealing system, and was 60 (°C·h) in the open system. The whiteness of glutinous rice decreased with the heat-moisture treatment. However, the whiteness of the heat-moisture treated rice was improved by reducing to 88% the percentage milling.

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Kokuto samples that have been traditionally produced in Okinawa Prefecture were dissolved in water and insoluble contaminants were removed by centrifugation. Water-soluble oligosaccharides contained in the supernatant fraction were subjected to charcoal and HP-20 columns to analyze the contained oligosaccharides. There were several oligosaccharides which were not digested by highly branched dextran glucodextranase, indicating that cyclic oligosaccharides are present in Kokuto. These oligosaccharides eluted at the same retention times as those of isomaltooligosaccharides composed of glucose units of 7, 8 and 9 (CI-7, CI-8 and CI-9) by HPLC analysis. These oligosaccharides were not digested by an α-amylase or by an α-1,3-glucanase but digested by an endodextranase. Mass spectrometry analysis also indicated that the molecular mass of these oligosaccharides was the same as those of CI-7, CI-8 and CI-9. We assumed that cyclic isomaltooligosaccharides exist in Kokuto, which human beings have been eating for long time.

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Starch granules are synthesized in a semicrystalline structure and have characteristic morphology and properties depending on the botanical origin and the organ of the plant. Surface gelatinization studies have shown that the internal structures of starch granules are not homogeneous and vary with radial locations, from the hilum to the periphery. The internal structure of maize starch granule coincides with the biosynthesis and development of starch granules and the expression of starch synthase activities during the maturation of maize kernels. The enzyme digestibility of starch granules relates to the internal structure and the internal surface area of the starch granule as revealed by confocal laser-scattering micrographs. Short branch-chains of amylopectin (DP 6–12) destabilize the granule structures, resulting in lobed or compound starch granules and small granules. Ratios of long branch-chains to short branch-chains of amylopectin molecules affect the shape of the molecule, e.g., cylindrical versus conical shapes. The shape of the amylopectin molecule may affect the packing of the molecules in the granule and, in turn, determines the morphology and the size of the starch granule.

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There are many kinds of polysaccharides composed of glucose, mannose, galactose, xylose, arabinose, glucosamine and so on. It is not so easy to follow their functions; however, it is possible to suggest them through some information on the physiology and/or ecology of microorganisms and plants. Generally, original skills, abilities, discoveries and ideas are also necessary in order to take large steps in research. I would like to introduce some attractive matters in the science of polysaccharides in addition to an explanation of the polysaccharides (succinoglycan, β-1,2-glucan, chitin, xyloglucan, β-1,3-glucan, amylopectin) examined. Furthermore, the utilization of biomass has been anticipated as a solution to the problem of the environment and polysaccharides are the main materials of biomass. A technique for the saccharification of polysaccharides to monosaccharides and a technique for fermenting monomers to useful materials like bioethanol should be studied.

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1. Developmental changes in starch properties of 9 plant species. Developmental changes in starch properties of 9 plant species (taro, Chinese yam, arrowhead, kiwi fruit, potato, squash, chestnut, Chinese radish and ginkgo nuts) were examined. By Scanning Electron Microscopy, the particle size of starch granules of the nine plant species were found to increase during the early developmental stage. The amylose contents of starch granules of the nine plant species tended to increase during the early developmental stage. X-ray diffractograms of starches could be divided into those showing pattern changes (taro, Chinese yam, chestnuts and ginkgo nuts), A-type pattern (arrowhead) and B-type pattern (kiwi fruit, Chinese radish, potato and squash) throughout development. The initiation temperature for gelatinization of taro, Chinese yam, arrowhead, Chinese radish and chestnut starches tended to be lower in the later stage of development than in the earlier stages. The initiation temperature for gelatinization of kiwi fruit, ginkgo nuts, potato and squash rarely changed throughout development. 2. Some properties of various starch granules. The mean particle size of konjac, taro, takenokoimo and bamboo shoot starch was 1.2-1.3, 1.4, 2 and 3.7 μm, respectively, being very small. The susceptibility of their starch granules to hog pancreatin was very high. The amylose contents of takenokoimo and taro starches as determined by the enzyme-chromatographic method were 10.8 and 13.5%, respectively, being very small. In contrast, the amylose contents of saffron, arrowhead and azuki bean starches were 29.2, 29.2 and 30.4%, respectively, being very large. The initiation temperature for gelatinization of katakuri and takenokoimo starches by photopastegraphy and differential scanning calorimetry were 44, 46.8°C and 73, 76°C, respectively. The former was the lowest, and the latter was highest. 3. Observation of various starch granules by Scanning Electron Microscope (SEM) and field emission scanning electron microscope (FE-SEM). On SEM starch granules in the slices of konjac bulbs (Zairai, Akagi and Haruna) were found to be polygonal in shape. In particular, the small polygonal granules in slices of Zairai were assembled like a soccer ball. The appearance on the surface of sotetsu trunk starch granules attacked by pancreatin was quite similar to that of normal maize starch granules. By FE-SEM observation, a string with the width of 20 nm was found on the surface of taro starch granules. 4. Gelatinization and swelling of starch as seen on imaging. Under a polarized-light microscope, the appearance of gelatinization and swelling of katakuri and potato starch and starch granules in slices of azuki bean cut by microtome was recorded with a video camera; then the video was edited to a speed 9-12 time faster to demonstrate the progression of changes in the image.

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Biochemical studies of enzymatic reactions using their inhibitors (substrate analogues) are useful for understanding the catalytic mechanisms of enzymes, especially those which are difficult to explain only by biogenetic investigations. We have presented the rational molecular design of the carbohydrate active enzyme inhibitors on the basis of Phillips’s lysozyme-subsite model. 1) α-Amylase inhibitors: We performed a chemo-enzymatic transformation of maltooligosaccharides into both-end-modified oligono-lactones to be of potential utility as substrate analogue inhibitors for mammalian α-amylase. The products were L⁴G2O, L⁴G3O and BG3O, which are competitive inhibitors for mammalian α-amylase. In this case, the lactone form was essential for the occurrence of an α-amylase inhibitor. Administration of L⁴G2O produces significant improvements in both blood glucose and insulin response, and this evidence will provide the support for its therapeutic potential in treating diabetes mellitus and obesity. 2) β-Glycosidase inhibitors: cycloalkyl β-D-glucopyranosides were synthesized by the transglucosylation of a β-glucosidase from fungi. Among three β-glucopyranosides synthesized, only CPEM-β-G was found to inhibit the sweet almond enzyme activity. As it is easily expected that CPEM-β-G is much more likely to inhibit the activity of an enzyme from plant origin compared with that from fungi, we studied the possibility of using CPEM-β-G as an inhibitor of the β-glucosidase activities of extracts from cut flowers on the basis of their kinetic data. Finally, we have presented an outline of our experiments for the investigation of some β-glycosylamidines (highly selective inhibitors of β-glycosidases) as the results of our joint research.

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