Rice flour can be substituted with powder from such starch-rich vegetables, as potatoes, sweet potatoes, taros and yams when making rice bread. We examined in this study, the effect of on staling of rice bread when substituting rice flour with potato powder. There was no difference in the specific loaf volume of bread with sweet potato, taro and yam powder substituting for rice flour and the control bread (100% rice flour). However, the specific loaf volume when substituting with potato powder was significantly decreased with increasing substitution ratio. The crumb hardness 3 days after baking was significantly lower than the control when substituting with sweet potato powder. Thermostable β-amylase included in sweet potato powder, produced a large amount of maltose by starch degradation during bread baking. Significant maltose was also detected in the crumb of rice bread substituted with sweet potato powder. We infer from these results, that maltose produced by β-amylase in sweet potato powder inhibited the recrystallization of starch, and prevented staling of the rice bread.

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Undesirable cooked rice called ‘mekko-meshi’ results when rice cooking is accidentally interrupted or raw rice is kept under warm conditions in a rice cooker. This study clarifies the effect of soaking conditions on the physicochemical and sensory properties of cooked rice. A Nipponbare rice sample was soaked in water for a soaking time of 0-12 hr at a water temperature of 20-90°C. The rice soaked at 65°C for 4 hr produced cracking on the ventral side of the rice grains, and the inner parts of the rice grains held more water than the outer parts. The surface stickiness and adhesiveness of the cooked rice after soaking in the 65-90°C range were less than the results for normal cooked rice. A sensory test revealed the texture of the cooked rice to be non-uniform and inferior after soaking in the 65-90°C range. The same effects were also apparent in old rice and Indica rice samples.

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Hardening due to retrogradation of the starch in rice flour gel limits the palatable lifespan of conventionally manufactured rice cakes and dumplings to only 2-3 days. This prompted us to investigate methods for slowing the aging process. The hardness of conventional 40% (w/w) rice flour gel increased within 2 days. However, adding a sugar (trehalose or maltose) to the gel made from the Awayukikomachi low-amylose cultivar slowed this hardening. Rice flour gel made by using Ohisa's method from Awayukikomachi or Yukimusubi flour (25%, w/w), maltose (25%, w/w), and water (50%, w/w) remained soft for 9 days, in contrast to traditional rice flour gel (24%, w/w) to which 28.6% (w/w) of maltose had been added. This new formula for rice flour gel has potential for use in the manufacture of rice cakes with a markedly extended usable lifespan.

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A good texture of fried food results from light deep-frying. Flour, egg and breadcrumbs are the basic materials used for the fried coating. We examined the effects on the fried coating texture of adding sodium hydrogen carbonate, albumen flour, mayonnaise, sake and crushed eggshells to the basic coating materials of flour and water. We also examined the effects on the fried coating of using frying oil (salad oil) mixed with lard. The weight ratio after heating, the solution separation rate, and the color difference were measured, and a sensory evaluation and compression test were conducted on these fried samples. Each sample was evaluated at similar levels for all parameters for comparison with the basic fried coating.

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The effects of how tea is brewed on its taste were investigated.
The amino acid and catechin contents in the tea solution were reduced with increasing number of times the tea leaves were extracted. Both the umami and astringent taste factors increased linearly with increasing amount of tea,umami increasing up to 10 g of tea leaves while astringency gradually increased beyond that concentration.
The astringency increased with increasing extraction temperature for the same tea leaves. The umami taste rapidly decreased to an extraction temperature of lukewarm water (40°C) and then there was little change up to an extraction temperature of boiling water (100°C).

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We assessed the control of oxidative deterioration when a high-voltage negative-ion generator (HNiG) was used during deep frying. Using the HNiG resulted in lower browning of the frying oil, and lower production of the trans-isomers of fatty acids than when it was not in use. The water content of bread being fried deceased rapidly when the HNiG was operating. Using the HNiG halved the contents of 14 types of such oil odour elements, as 2,4-decadienal and 2,4-heptadienal. Natural cooling progressed more rapidly when the HNiG was operating as the deep fryer was switched off, suggesting that there was an increase in the fluid flow of the frying oil.

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The palatability and antioxidative activity of a Nikkan-bancha infusion (Japanese traditional tea in Oyodo-cho, Nara) was evaluated to compare with green tea and roasted green tea. The aroma of Nikkan-bancha was measured by an electronic nose system to show greater similarity to hydrogen sulfide, organic acid and aldehyde, and a higher intensity of the aroma index than green tea and roasted green tea (p < 0.01). A sensory evaluation showed that the aroma of Nikkan-bancha was gentl and less forceful. Although the taste sensor showed less umami, and astringency, and more bitterness, the sensory evaluation showed higher more umami and sweetness, and less astringency. It was suggested that the astringency weakened umami and sweetness, but strengthened bitterness in the sensory evaluation of the tea infusion. The antioxidative activity of Nikkan-bancha was measured to be about half that of green tea.

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