Diabetes is a lifestyle disease, and its prevention and treatment are extremely important. Since Hoku243 presents fewer short-branched glucans and more long chains in the amylopectin starch, its starch is resistant to gelatinization and the boiled rice grains are non-sticky and brittle. The prevention of abrupt increases in postprandial blood glucose level (BGL) after consumption of Hoku243 (produced by high pressure treatment (HPT) after soaking in unsalted rice koji miso) was investigated in Sprague-Dawley (SD) rats. The BGL at 90 min and area under the curve (AUC) for 120 min after eating were significantly lower in SD rats fed Hoku243 than those in rats fed the control diet, consisting of Koshihikari rice (1% or 5% level). The addition of glucose, glutamic acid, and dietary fibers by soaking in an unsalted rice koji miso (unsalted miso) suspension made the boiled rice tasty and harder. After HPT, the texture of the boiled rice grains became harder, but sticky, which made the rice acceptable in terms of palatability and bio-functional in terms of digestion delay. It is now possible to produce palatable and bio-functional boiled rice grains by HPT and soaking in unsalted miso.
Application of a real-time PCR system for the detection of blending and the quantification of the blending ratio of rice was investigated. Quantitative measurement by real-time PCR was performed using two types of primer sets ; one was an improved rice cultivar identification kit, while the other was newly developed for the determination of total amount of rice DNA. Calculation formulae for blending ratios were developed based on standard curves of both primer sets. These formulae were verified using DNA solutions extracted from the Koshihikari containing 5% or 25% of another rice sample. Calibration errors were less than 30% of the expected values.
Rice production is about 755 million metric tons (as paddy) in the world per year, and one of the most important crops because it supplies about half the energies of all the calories from foods to the human being. As a staple food, high-yielding and high-palatability is very important properties for rice. In 2013, Japanese traditional dietary culture, "Washoku", was registered as a cultural heritage by UNESCO. Rice is one of the main food materials of "Washoku", which is harmonized well with nature, and prepared using seasonal and regional characteristic agricultural and marine products. Family members, friends, and community residents enjoy "Washoku" on special days, such as festivals, ceremonies, etc. In Japan, high-yielding rice cultivars were bred until 1970s to secure the food supply, but high-quality rice became more necessary since 1980s because of economic growth and diversification of food habit. Eating quality of rice is evaluated by the sensory test and physico-chemical measurements. As some dishonest rice retailers mislabeled low-quality rice as premium rice, we developed a PCR method to authenticate rice cultivars. It became possible to identify the seed varieties in the rice products, such as cooked rice, as samples. Recently, Japanese government developed various kinds of "specialty rice" cultivars to enhance the utilization of rice as the rice consumption has been decreasing in Japan. Japanese consumers have become interested in rice cultivars which promote health lately. Therefore, the market of bio-functional rice, such as low-protein rice, high-resistant-starch rice, or germinated brown rice, is promising in Japan. Food products can be labeled with health claims as the "Foods with Function Claims" when supported by clinical trials or the systematic reviews. Many researchers, in Japan, are now trying to develop the healthy rice products to prevent diabetes, hypertension, or dementia using new rice cultivars as materials.
We developed an enzymatic colorimetric method for the quantification of α-D-mannose 1-phosphate by adding phosphomannomutase, mannose 6-phosphate isomerase and glucose 6-phosphate isomerase to a conventional glucose 6-phosphate assay using glucose 6-phosphate dehydrogenase. In this method, α-D-mannose 1-phosphate is converted into D-glucose 6-phosphate via D-mannose 6-phosphate and D-fructose 6-phosphate and the resultant D-glucose 6-phosphate is ultimately converted into 6-phosphogluconolactone under concomitant reduction of thio-NAD+ to thio-NADH, which can be quantified by its wavelength of 400 nm. This method is not altered by the presence of D-mannose, D-mannosamine, N-acetyl-D-mannosamine, L-mannose, β-1,4-mannobiose, α-1,2-mannobiose, methyl α-D-mannoside or dimethyl sulfoxide and it would be useful in studies involving enzymes such as phosphorylases belonging to glycoside hydrolase family 130, which release α-D-mannose 1-phosphate as the reaction product.
