In order to improve air pressure utilization and working performance, the direct seed-metering device for rice was designed with spoiler blades embedded in the air cavity. The study was carried out using theoretical analysis and hydrodynamic methods to obtain the optimum structure of the spoiler blades. Taking the rotating speed of the air cavity, the negative pressure of the air cavity, and the filling height as the test factors, the multiple regression analysis and the response surface analysis were carried out to obtain the best working parameters of the seed-metering device with spoiler blades. The results showed that when the rotating speed of the air cavity was 23.56 r/min, the negative pressure of the air cavity was 4.97 kPa and the filling height was 12.82 cm, the qualified index was 95.21%, the missing index was 3.28% and the multiple index was 1.51%, which was the best seeding performance. Comparing the test with the seed-metering device without spoiler blades, the results showed that the installation of spoiler blades can improve the performance of the seed-metering device under the best working parameters. This study provide a reference for the design of direct seed-metering device for rice.
This article is purposed mainly to analyze the drying characteristics in the internal moisture of rice at different drying temperatures using low-field NMR. The signals of the relaxation time were applied to determine the moisture content and dynamic characteristics of various phases. According to the experimental results, the migration of strongly chemically bound water and other phases of water was a bi-directional process. The first half of the process can be dried at high temperatures to remove moisture rapidly, while the second half can be lowered to reduce the moisture gradient. Besides, the first half was dried at 65 C and the second half at 35, 45 and 55 C, which led to an increase in energy consumption by 9.62%, 6.99%, and 2.54% as well as an extension to the drying time by 65, 40, and 18 min. The results will provide a theoretical basis for optimizing the drying process for rice. Practical ApplicationsLow field nuclear magnetic resonance was applied to study the drying characteristics of rice, and to determine the variation pattern and migration characteristics of water in different phases of rice with varying temperatures during the drying process. On this basis, a high-quality variable temperature drying method was proposed. Moreover, this method is applicable to the variable temperature of the rice drying process.
In order to improve the content of GABA in japonica rice, so as to improve the nutritional composition and enhance the added value of rice, this study explored a combined process of low-pressure steam enrichment of γ-aminobutyric acid (GABA) content in japonica rice and low-pressure superheated steam (LPSS) drying of japonica rice. The low-pressure energy and the energy stored in rice grains were used to promote water absorption and activation of rice germs in a steam environment. Under the action of glutamate decarboxylase, the germ glutamate underwent an enzymatic reaction to generate GABA, which was transferred to and stored in the rice endosperm due to the concentration gradient and water gradient. After germination, LPSS was successively applied to dry the rice grains. The response surface method was used to optimize the parameters of low-pressure wet steam enrichment and LPSS drying of the rice grains. The experimental results showed that when the pressure was 0.026 MPa, the temperature was 60.66°C, the time was 5.01 h, and the flow rate was 0.31 L/h; the GABA content produced by low-pressure wet steam germination of japonica rice peaked at 94.1751 mg/100 g. When the germinated and enriched japonica rice was put through LPSS drying with a pressure of 0.021 MPa, a temperature of 66.55°C, a time of 1.57 h, and a flow rate of 0.28 L/h, the GABA content peaked at 104.161 mg/100 g. The results show that the combined process of low-pressure steam enrichment and drying continuously produced GABA in the soaking enrichment and drying stages, and the content of GABA in the drying stage accounted for 10% of the total content, which effectively increased the content of GABA in japonica rice and shortened the enrichment time. This study provides a technical reference for industrialized production of GABA-rich brown rice, embryonic rice, and polished rice.
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