Kaoru Sakamoto

[Purpose] Previous studies have shown that sake lees are rich in ingredients derived from raw materials and their metabolites, which are by-products of the sake brewing process, a traditional Japanese technique. Additionally, studies have indicated that sake lees possess health benefits. However, the disposal of sake lees has recently become a challenge due to their limited applications and shelf life, as well as shifting food preference, particularly among the younger generation. Hence, this study focused on mature lees, which can be stored for a long time and have a unique flavor, and the microorganisms in them. The study also reported changes in nutrients and functional ingredients produced by aminocarbonyl reactions and microbial activities during storage. This study further explores cooking methods that utilize the unique ingredients and flavors of sake lees to expand their applications. [Method] The samples were provided by a sake brewer in Hyogo Prefecture who brews using the traditional natural fermentation inherited from the Edo period (1603-1868). They were obtained during the sake brewing process using Yamada Nishiki rice from Hyogo. Previously, we reported on sake lees stored for 50, 100, and 200 days at room temperature, along with a separate sample of 3-year lees. We compared six types of sake lees including 1000-day lees with an extended storage period. In addition, we isolated and cultured bacteria in the sake lees and 200-day lees, and identified the species by the 16SrRNA gene analysis. Based on these results, we analyzed the cooked products made from sake lees and stored lees. [Results and Discussion] The genetic analysis identified two bacterial species in both sake lees and 200-day lees. One is B. subtilis which includes natto bacteria, and the other is P. megaterium, commonly found in fermented foods and wine. The latter produces vitamin B12, which explains its abundance in sake lees, despite its low concentration in raw rice. To promote broader use of sake lees, we explored cooking methods such as heating or pairing them with cheese or citrus fruits to balance their characteristic flavor and improve their appeal.

[Objective] Various confections such as fondant and whiskey bonbons are made by utilizing the phenomenon of sugar recrystallization. One of these confections, glaze, is made by adding water and liqueur to powdered sugar and is used to coat baumkuchen and donuts. The cause of the stickiness of glaze during storage has not been clarified, and there have been no studies that have investigated the crystalline state of glaze in detail. Therefore, in order to clarify the cause of the stickiness of glaze, we focused on the amount of reducing sugar and the crystalline state of sugar. [Method] Glazes were prepared using three types of powdered sugar from different sugar refiners. X-ray diffraction, reducing sugar, viscosity, and weight change under low and high humidity conditions were measured for the powdered sugar and glaze, and observations were performed using a polarizing microscope and SEM, and HPLC analysis was performed. [Results and Discussion] The three types of powdered sugar showed similar XRD waveforms. Microscopic observation revealed that the glaze was in a state where amorphous and crystalline substances coexisted. It was confirmed that powdered sugar contains trace amounts of reducing sugar, so the effect of reducing sugar on glaze quality was examined. Glazes without added reducing sugar were less affected by humidity even under high humidity conditions, but glazes with added reducing sugar were prone to drying out in low humidity environments and absorbing moisture in high humidity environments. The crystals in the glaze with added reducing sugar were small, and the reducing sugar hindered the recrystallization of sugar. When the glaze with added reducing sugar was separated into aqueous and solid portions and analyzed by HPLC, the proportion of reducing sugar was higher in the aqueous portion, making it clear that reducing sugar is involved in hygroscopicity. It was found that reducing sugar hinders sugar recrystallization and promotes moisture absorption reactions under high humidity conditions, thereby reducing the quality of the glaze.

Purpose: According to the survey of recipes for Akashiyaki in the previous report, the proportions of flour, egg, and dashi soup in Akashiyaki varied depending on the recipe, and for flour, there were recipes using only wheat flour and recipes using wheat flour and wheat starch (Ukiko, Jinko). Since there are different kinds of wheat starches with different particle sizes, we prepared Akashiyaki using four kinds of wheat starches with different particle sizes from wheat flour and compared the effect of flour on the properties of Akashiyaki. Methods: Four kinds of wheat starches with different particle sizes were used as wheat flour. The ratio of powder: egg: dashi stock =0. 8:1:3 was used and baked in a takoyaki pan. At a measurement temperature of 20°C., the following were measured: height, mass, breaking load, breaking strain, stress at 10% and 20% strain, color difference, salinity, and sensory evaluation. Results: Wheat flour was slightly higher in Akashiyaki than wheat starch, lighter in mass, higher in breaking strain and breaking load, higher in a* and b* values of color difference, and was evaluated as having a darker yellow color, being the toughest, and being easier to chew. Among wheat starches, the higher the particle size, the higher the Akashiyaki, the lower the b* value, and the paler, firmer, and stickier yellow color in the sensory evaluation. These results suggest that the gluten content of wheat flour and the viscosity of wheat starch are higher than those of wheat starch. There was no difference in the salt content of Akashiyaki depending on the type of flour, but in the sensory evaluation, the taste of dashi soup was stronger in wheat starch than in wheat flour. This may be due to the fact that wheat starch contains less protein than wheat flour, and Akashiyaki made with wheat starch seems to be softer. The characteristics of the powder affected the taste of Akashiyaki.

Objective: We believe that germ-sprouted rice aims to combine the good taste of polished rice with the nutritional value of brown rice. Although embryo bud milled rice containing 80% or more embryo buds is distributed as rice whose nutritional value is guaranteed, its consumption does not account for a large percentage of the total rice consumption. Therefore, with the aim of expanding the use of germ rice, we examined the rice characteristics of easy-to-eat germ rice that are different from those of conventional germ-polished rice. Methods: Two types of germ rice with different germ retention rates and polished white rice were pounded at Touban Co. The water absorption rate, color difference, texture, reducing sugar content, and GABA content were measured and sensory evaluation was conducted for the germinated rice. Results and Discussion: The germ retention rates of the two types of germ rice were 52.8% and 43.5%, respectively. When the water absorption was measured at 5°C and 40°C, the germ rice had a higher water absorption rate at both temperatures. In addition, water absorption at 5°C was higher than at 40°C. The higher water absorption of the germ rice was thought to be due to the difference in the method of pounding. The color difference ΔE between germinated rice A and B was found to be 1.41, which was enough to visually recognize the difference, and there were significant differences in L* and a* values. In the texture measurement, no difference in hardness was observed in comparison with polished rice. The reducing sugar content indicated that the sweetness of the germinated rice increased after prolonged soaking, and the GABA content of the germinated rice was lower than that of the brown rice but higher than that of the polished rice, and the amount varied depending on the cooking method. In the sensory evaluation, significant differences in whiteness, gloss, aroma, and overall evaluation were observed between the two types of germ rice, indicating that even a 9.3% difference in germ retention rate significantly affected the evaluation.