1. With the development of “Rural revitalization”, China’s grain output has ranked first in the world, reaching a new high and remaining stable at over 1.2 trillion jin for nine consecutive years.[...

To optimize the microwave drying process of paddy rice and improve its quality, the effects of hot air temperature, microwave power, and grain layer thickness on the post-drying potassium content, calcium content, vitamin B₁ content, and free fatty acid content of rice were investigated. Using response surface methodology, an experimental scheme based on the Box-Behnken design was constructed to analyze the influence of these three factors on the four nutritional and biochemical indicators. A multi-index optimization model was established and validated. The results showed that all response indicator models were statistically significant. The optimal process parameters were determined as follows: hot air temperature of 52.47°C, microwave power of 20 kW, and grain layer thickness of 2.78 cm. The corresponding predicted values were potassium content of 3724 mg/kg, calcium content of 113.7 mg/kg, vitamin B₁ content of 0.290 mg/100g, and free fatty acid content of 21.5 mg/100g. Validation experiments demonstrated that the dried rice under these conditions exhibited excellent quality, with relative errors between predicted and measured values below 3%, indicating the reliability of the model and the significant improvement in rice drying quality achieved by the optimized process. Furthermore, visual process reference charts were developed to provide a theoretical basis for adjusting process parameters in practical production.

To enhance the uniformity and efficiency of rice drying, an infrared hot air combined drying test bench was developed, and the air flow distribution inside the pipeline was optimized to achieve efficient and uniform drying. The pipeline structure was optimized by using computational fluid dynamics simulation technology, with relative standard deviation (CV) and uniformity index (UI) as evaluation indicators. The airflow uniformity of the optimized pipeline and the temperature uniformity of the drying chamber were verified through experiments. The numerical simulation results showed that after the structural optimization, the UI of the pipeline outlet was increased from 92.27% to 97.23%, and the CV was decreased from 22.34% to 14.62%. Experimental verification shows that the wind speed uniformity index of the optimized pipe section is 97.67%, which is in good agreement with the simulated value (the relative error of the average speed is 1.50%), and the temperature change in the drying chamber is stable within ±2.5%. Further drying performance tests were conducted on two types of rice. Under the conditions of a hot air temperature of 45℃, a wind speed of 3 m/s, and a thin layer thickness of 20 mm, the performance of infrared hot air combined drying and hot air drying was compared. The performance test results show that the infrared hot air combined drying only takes 120 minutes, which is 18.75% shorter than the single hot air drying time, and still maintains a relatively high drying rate during the deceleration and dehydration stage. Improving the uniformity of air flow distribution can significantly enhance the uniformity of drying. Infrared hot air combined drying has good application potential in terms of improving efficiency and energy conservation.

In order to research the drying and adsorption characteristics of banana. Experiment on banana slice drying and absorption were analyzed in the article. The vacuum drying was used in the banana slice drying experiment. In drying experiment, moisture of banana slices decreased at 75°C in 151 minute. G1 weight decreased from 33.95g to 28.99g and G2 weight decreased from 33.51g to 28.8g. In absorption experiment, the weight of banana slice increased from 28.99g to 30.75g.When the humidity reached balance between the banana slice and the atmosphere, banana slice weigh had no changes. Banana slice surface has a huge difference in character before and after drying. The sorption process in some materials was irreversible because the entropy changed during the adsorption and desorption process.