Glucoamylase (EC 3.2.1.3) from Endomyces sp. IFO 0111 was bound with CM-cellulose at pH 4. The amylase activity in the bound form was found to be less than 2.5% of that in soluble state, and the bound enzyme was more labile to heat- and urea-treatment. However, the bound enzyme could be quantitatively liberated into solution at pH 6. Thus, the enzyme which had acted in solution at pH 6 could be recovered simply bylowering the pH and repeatedly used for another action at pH 6. When the glucoamylase was adsorbed on hydroxyapatite, it showed 10% of the amylase activity and 45% of the maltase activity, as compared with the corresponding amount of the enzyme in solution. K_m and V_max values of both states of the enzyme were determined for soluble starch and maltose. The enzyme increased its heat-stability upon being adsorbed on hydroxyapatite. Both types of the bound enzyme could be dried to stable powders in the presence of a high concentration of sugar.

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Superscope (recently developed by Nippon Denshi Co., Ltd.) was used in this study. Starch granules from adzuki bean (Phaseolus chrysanthos) and smooth bean (Pisum sativum var. arvense) were molded into replica by use of Bioden R. F. A. (acetylcellulose film of Ôken Shoji Co.), Bioden was softened by the vapor of methyl acetate, and the sample granules were molded by their own weight. This method or the so-called self-molding method was presumed to cause less physical deformation on the samples than the method of methacrylate resin coating reported formerly (Part X, 1968). Satisfactory results were obtained at relatively lower magnifications of 2000-5000.

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A Scanning electron microscope JSM-2 (Nippon Electron Co., Ltd.) was used in order to investigate stereoscopically the surface structure of starch granules from adzuki bean (Phaseolus chrysanthos), smooth pea (Pisum sativum var. arvense), and potato. The surface structure of starch granules was observed far more satisfactorily by this technique than by the conventional replica method. The characteristic fissures of legume starch granules were observed more clearly in case of adzuki bean starch by this technique than by the replica method. It was not clear whether the fissures were on the surface or inside of the granule by an optical microscope. It has now been clarified that the fissures of starch granules of adzuki bean starch were on the surface of the granules.

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Starch pastes (5%), which were prepared by heating at 100°C for 5 and 30 min, were kept at constant temperature of 10°C intervals between 70s and 0°C for 60 min. The rates and extents of retrogradation of the pastes were measured by the method of glucoamylase digestion (A-method) and iodine binding (I-method). The hot potato and sweet potato starch pastes were estimated to be 100% gelatinized form (a-starch) by the both methods. Though the hot corn and wheat starch pastes were estimated to be 100% a-starch by A-method, the pastes were estimated to be approx. 90% a-starch by I-method even in 30 min-heated pastes. The facts suggest the remains of a partly aggregate form of amylose in these cereal starch pastes. In general, the rate of retrogradation increased rapidly as the temperature was lowered and was max at 0°C. A leading role of amylose in retrogradation was indicated since more intence retrogradation was noted by I-method than by A-method. The temperature dependence of retrogradation of amylose was characteristic by the source of starch. The rates of retrogradation of the corn, wheat, potato and sweet potato starch pastes were increased rapidly below the temperature of 50-60°C, 40-50°C, 10-20°C and 10°C, respectively. No detectable retrogradation occurred in waxy rice and waxy corn starch pastes under the present experimental conditions.

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Gelatinization curves of cereal starches obtained by plastograph have higher viscosity than those of root or tuber starches, and have characteristic steep viscosity descent at about 95°C. Cereal starches have more fatty acid which can hardly be extracted by ethylether. In this paper, the effect of fatty acid upon plastogram of starch suspension was studied through defatting and restoration of fatty acid to cereal starch or adding it to sweet potato starch. Consequently, fatty acid was found to rise the gelatinization temperature higher, increase the peak viscosity and cause the steep viscosity descent. These facts might mean that fatty acid repress swelling by forming amylose-fatty-acidcomplex, but at high temperature the complex dissociates and the starch granule disperses which causes the steep viscosity descent. Furthermore, the effects of amount and kinds of fatty acid upon plastogram were studied. The most effective complex former was palmitic acid having the highest peak viscosity and the highest dissociation temperature. Myristic and Oleic acid were similarly effective complex formers. These effects were in proportion to the amount of fat-by-hydrolysis impregnated into starch granule. The insoluble starch particles remained in the enzymatically saccharified starch solution of cereal starch could be explained by introduction of amylose-fatty-acid-complex which dissociates at about 95°C.

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The gelatinization properties of heat-dried and heat-moisture-treated starches were studied by Brabender amylograph and plastograph.1) Amylograms of heat-dried starches could only detect the decrease of viscosity, but plastograms could detect the descent of gelatinization temperature and the decrease of viscosity. When corn starch was dried at 120sC for 20 hours, the whole viscosity curve of plastogram was descended greatly indicating decomposition during heating, and potato starch was more sensitive.2) On plastogram of heat-moisture-treated corn starch, initial gelatinization temperature did not change, but terminal gelatinization temperature rose and peak viscosity decreased. Plastogram of heat-moisture-treated potato starch had a characteristic viscosity curve detecting partial gelatinization and repression for dispersion. Being gelatinized, the temperature where the viscosity began to increase lowered widely, but the longer became the treating time, the higher became the temperature .3) On plastogram, heat-moisture-treated corn starch with 18% moisture did not gelatinized, but potato starch with the same moisture gelatinized during treatment. So, plastogram can detect gelatinized starch more sensitively than X-ray diffractmetry.

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The ability of heat inflation of various starch paste which were gelatinized at 100°C in highly concentrated starch suspension by plastograph and dried at room temperature were studied. The effects of gelatinization temperature upon the volume of heat inflation of starch were also tested. 1) The largest heat inflation of starch paste was potato starch; 7.7 times of initial volume. It was followed by tapioca, sago, waxy corn, sweet potato, rice, corn and wheat starch in the order of larger inflation. The order of heat inflation was similar to that of peak viscosity in amylogram, not in plastogram. 2) Next, the volume of heat inflation of starch paste gelatinized at various temperature was examined. Potato starch had two peaks of inflation volume at 70°C and 90°C of gelatinized temperature, however, every other kind of starch had only one peak, such as sweet potato at 90°, waxy corn at 95°, and corn starch at 100°C respectively.

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