This fundamental study investigated a method to control deterioration in the quality of edible oil through autoxidation of its unsaturated fatty acid content by adding the natural food materials, green tea powder and pumpkin powder, at levels between 1 wt% and 5 wt%. The experiment was carried out at 40 °C for 12 days. The results showed that adding green tea powder at a level of 5 wt% limited the maximum peroxide value (POV), a measure of the primary products of autoxidation of unsaturated fatty acids, to 51%; reduced the carbonyl value (CV), a measure of the secondary products of the oxidation of unsaturated fatty acids, by 76%; and suppressed oxidative rancidity by 85%. Adding pumpkin powder at a level of 5 wt% reduced POV and CV by up to 15% and 32%, respectively, and oxidative rancidity by 36%.

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 We developed a novel approach for analyzing chewing vibrations in which vibration signals are isolated as short vibrations called cracklets and analyzed based on the frequency domain of each signal. The results of an oral stimulus test demonstrated that the perception of food texture was evoked only when the vibration stimuli were presented without actual food consumption. A discrimination test in which we used a discrimination ratio to examine the differences between the original chewing vibrations and modified vibrations created by deleting some cracklets demonstrated that segments of normalized cracklet energy affected the sensory texture perception of rice crackers.

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 Jerusalem artichoke tubers contain a functional ingredient called inulin. Processed foods, such as tea made by roasting these tubers, have been developed. In this study, we evaluated the color, inulin content, and taste quality of tea made from roasted Jerusalem artichoke tubers that were steeped at different temperatures and time periods and examined the conditions at which there was high palatability and inulin content. On increasing the steeping temperature and time period, the tea became darker and the inulin content increased. Regarding taste quality, the umami taste increased to such an extent that humans could distinguish the difference in taste with the increase in steeping time, while the changes in the bitter and astringent tastes were small. In the sensory evaluation, no difference in taste was observed in each condition. The results indicated that steeping tea in hot water for 2 min or longer or steeping it in cold water for 2 h or longer would produce a generally preferred tea color and high inulin content.

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