Sudachi, Citrus sudachi, is a major local food in Tokushima Prefecture, and over 98% of this fruit is produced in Tokushima Prefecture. After juice is extracted from sudachi, sudachi peer is not used effectively. Sudachitin, a polymethoxylated flavone is isolated from sudachi peer, and its structure is similar to nobiletin, which possesses anti-inflammatory and anti-obesity actions. First, we evaluated the effect of sudachitin on lipid and energy metabolism in mice fed a high-fat diet. C57BL/6J mice were fed a high-fat diet treated with 5mg/kg/day sudachitin orally for 12 weeks. The mice treated with sudachitin showed significantly decreased body weight gain, body fat and viscera fat compared to that of mice fed a high-fat diet. Moreover, sudachitin improved glucose intolerance and insulin resistance in these mice. We concluded that sudachitin may improve metabolic syndrome by enhancing energy metabolism. Purified sudachitin cannot be used as a food ingredient because of the possibility of side effects and it is too expensive for clinical use at present. Therefore, we tried to produce a sudachi powder which contained sudachitin at high concentration from the dried sudachi peer containing a low amount of sudachitin. It is possible to adjust the content step-by-step from 1% to 80%. We also evaluated the function of sudachi peer extract powder using an animal model of obesity. The mice treated with sudachi peer extract powder showed significantly decreased body weight gain compared to that of mice fed a high-fat diet.

We evaluated the taste intensity of various sugar products derived from sugar cane using a taste sensing system and confirmed the relationship against sensory testing as well as the components present. Measurements were conducted with various sensors of the taste sensing system. As the taste information values for salty taste (first taste of CT0 sensor), umami koku (savory “fifth” and rich taste) (aftertaste of AAE sensor), and mineral bitterness (aftertaste of AN0 sensor) could be obtained in all specimens used for testing, these three sensors were selected. In addition, it was confirmed that these three taste information values are lower in refined sugar and higher in brown sugar and kokuto, and were dependent on the compounding ratio of kokuto, which suggests that these values can be used to evaluate differences in sugar products derived from sugar cane. Subsequently, a PC1 score was obtained by principal component analysis of these taste information values. It showed a high positive correlation (r＝0.981) with the intensity of kokuto taste in sensory testing. This suggests that the intensity of kokuto taste in sensory testing can be evaluated with the taste sensing system and can be used as a kokuto taste index. In addition, the PC1 score and the intensity of kokuto taste in sensory testing showed a high positive correlation with cation (particularly potassium), anion (particularly sulfate), and polyphenol contents, and a high negative correlation with saccharine content (particularly sucrose). Positive correlations were thus observed for the basic substances of salty taste and mineral bitterness.

We conducted sensory testing and taste evaluation using a taste sensing system of kokuto (non-centrifugal cane sugar) produced in Okinawa and Kagoshima, and confirmed the relationship between the results and the components present. According to sensory testing, kokuto produced in Okinawa generally has strong egumi (bitter and astringency taste) and a relatively similar taste. On the other hand, kokuto produced in Kagoshima has different strength of egumi and a characteristically distinct taste other than egumi, depending on the island where it is produced—that is, its taste quality is not similar. It has become clear that the strength of the taste information values for salty taste, umami koku (savory "fifth" and rich taste), and mineral bitterness can be evaluated by selecting the appropriate sensor in the taste sensing system. With regard to these values, kokuto produced in Okinawa generally showed higher values, while kokuto produced in Kagoshima has a different balance depending on the island where it is produced. This tendency mirrors the results of sensory testing. In addition, PC1 scores obtained by principal component analysis of the taste information values coincide with those of sugar products derived from sugar cane (kokuto taste index) obtained in a previous report at a relative coefficient r＝1.000. This suggests that kokuto taste index can be used as an indicator for measuring the taste intensity of sugar cane-derived kokuto. We measured saccharide, polyphenol, and mineral contents in kokuto and color differences, and conducted principal component analysis of the mineral contents. These contents are correlated with kokuto taste index, and minerals, which are substantially present in kokuto, have a particularly strong effect on the intensity and quality of taste.

Water often controls the processability and preservability of foods, especially those of the low-water content, by means of mobilities of water and food polymer molecules. Glass transition is a concept of dynamics governs the mobilities and physical properties of foods as well. An explanatory address with a focus on the glass transition in foods was then presented in this workshop.

Solid food products are typically in an amorphous state, and their physical properties change dramatically at the glass to rubber transition temperature (T_g). T_g decreases with increasing water content because of water plasticizing effects. When T_g becomes lower than the ambient temperature, a glass to rubber transition occurs at the ambient temperature. The water content at T_g＝25°Cis usually described as the critical water content (w_c). In this review, the effect of glass to rubber transition on the texture of cookies, the caking of mango powder and the compressibility of soup powder is explained. T_g of the food samples was evaluated by differential scanning calorimetry or thermal rheological analysis. w_c was determined from the relationship between T_g and water content. Fracture properties of the cookie samples changed from brittle to ductile at w_c. Caking of mango powder occurred at water contents above w_c. Hardness of soup powder compressed at temperatures above T_g was much higher than when compressed at temperatures below T_g.