The gel strength of potato starch-corn starch mixed gels was studied, and the following results were obtained.
1) The gel strength of mixed starch gels increased 10-20% higher than the controls, when 10-50% of corn starch was admixed with potato starch.
2) The microscopic observation indicated that corn starch granules remained as swelled particles in the mixed starch gel, while mixed wheat starch or waxy corn starch granules did not remain.
3) The change of the gel strength of the mixed starch gel during preservation under low temperature after heating up to 85°C, was similar to that of potato starch gel, while, after heating up to 120°C, similar to that of corn starch gel.
These suggests that swelled corn starch granules in mixed starch gel contribute to the gel structure as a filler and as a result the gel strength increases markedly.

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Sensory evaluations of cooked rice were carried out and physicochemical properties of milled rice were measured simultaneously on thirty-four kinds of non-glutinous rice harvested in 1982.
Then, palatability evaluation (overall in sensory evaluations) was taken out as criterion variable and twenty-one items of physicochemical properties were picked out as predictor variables, and multiple regression analysis was carried out.
As the results, multiple regression equation was obtained as follows.
y=-0.12716x₃-0.09285x₆+0.09020x₇+0.09457x₉-6.59552x₁₄+2.64251 (coefficient of determination: 70.14%) Using this multiple regression equation, palatability of rice can be passably estimated by measurement of five items of physicochemical properties; namely, protein of milled rice (x₃), maximum viscosity (x₆), minimum viscosity (x₇) and breakdown (x₉) in amylographic characteristics of milled rice flour, and starch-iodine blue value of residual liquid (x₁₄) in cooking quality of milled rice.
Moreover, adequacy of this multiple regression equation was investigated on eighteen kinds of non-glutinous rice harvested in 1983.

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[in Japanese]

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This review deals with two kinds of physical modifications of starch which have been socalled “warm water treatment” and “heat-moisture treatment.”
A temperature-composition diagram illustrating the gelatinization and the melt of starch granules has been constructed from the DSC data that show two kinds of endothermic transitions for the starch-water system. The diagram obtained corresponds to that of the crystalline polymerpoor solvent (diluent) system. Thermal phase transitions of the starch-water system have been discussed using the diagram.
The effect of warm water treatment on starch granules has been studied: This treatment causes the sharpening and the rise of the gelatinization temperature range, and the reduction of the swelling power and the solubility. The structural changes in granules during the treatment have been interpreted in terms of the annealing of semicrystallites of starch molecules. In fact, photomicrographs presented in the paper well shows the annealing process of starch granules with increasing temperature. It was concluded that this treatment brings about increases in homogeneity of both individuals and populations of starch granules through the process of annealing of starch crystallites.
Heat-moisture treatment brings about changes in the physical properties of starch through the process of the “melting” of starch granules. In the case of potato starch, the “B” pattern of X-ray diffraction is changed to “A” or “C” pattern, involving increases in heterogeneity of granular structure. The gelatinization properties of potato starches treated at various moisture levels and temperatures were examined and the relationships between the treatment conditions and the gelatinization properties have been clarified. From the results, it was concluded that heat-moisture treatment brings about irreversible disordering of granular structures with increasing of associative forces among starch molecules in granules.
Degradation of the physically modified starches with amylases and mineral acids were also studied. Susceptibility of heat-moisture treated potato starches to amylases was much larger than that of untreated one, but not in the case of corn starch. Microscopic observations by SEM showed that the degradation of the treated potato starch with glucoamylase from R. niveus and α-amylase (liquefying type) from B. subtilis (BLA) proceeded in the different mode each other. Differences in the action mode of BLA on the digestion of corn and the treated potato starch were also shown. In contrast to the heat-moisture treated potato starch, the warm water treated potato starch showed less susceptibility to amylases than the untreated one did. Some scanning electron micrographs of acid-modified potato starch granules were also presented.
In conclusion, the possibilities of the utilization of the physically modified starches were described.

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The basic concept and outline of the subsite theory were described, which correlates quantitatively the subsite structure (the arrangement of subsite affinities) to the action pattern of amylases in a unified manner. The subsite structures of several exo- and endo-amylases and an α-glucosidase were shown in histograms, from which the binding modes of linear substrates and glucose can be predicted.
The theory is effectively utilized as follows: 1) Interpretation of the substrate specificity of the amylase. 2) Calculation of the change in product distribution in the course of hydrolytic reaction catalyzed by the amylase. 3) Characterization of the nature of subsites by spectroscopic methods and chemical modification. 4) Prediction of change in action pattern by chemical modification. 5) Detailed analysis of mechanisms of amylase-catalyzed reactions by fast reaction techniques.
Several actual examples of application of the theory to amylases, including glucoamylase, Taka-amylase A and bacterial liquefying α-amylase, were described.

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