Genomics and Applied Biology 2026, Vol.17, No.1, 16-25 http://bioscipublisher.com/index.php/gab 18 2.2 Types and operating modes of mechanical drying The method of mechanical drying involves using hot air to gradually remove the moisture from the rice grains (Chen et al., 2017). Commonly used equipment for farmers includes flat-bed type and tower type. There are options using coal, gas, or electricity. Small-scale grain producers mostly use intermittent operation, processing one batch at a time; larger grain processing centers tend to adopt continuous operation, with a larger processing capacity. This study selected a circulating flat-bed dryer. The temperature is controlled at around 45 ℃, and the drying stops when the moisture content drops to 14.5%. This method does not depend on weather conditions, dries quickly, and saves manpower. However, the investment in equipment and energy consumption is considerable. If the temperature is not controlled properly, it may also affect the quality of the rice (Wang et al., 2020). 2.3 Realistic constraints for farmers' choice of different drying methods In actual production, farmers do not first consider which method is "more advanced", but rather they first assess whether they can afford it (Peng et al., 2018). Once the funds and conditions are laid out, the choice usually becomes clear. Drying in the sun costs almost nothing, so small-scale farmers are more likely to use it, but this method is highly dependent on the weather. The thickness of the drying layer and the number of times it is turned must be closely monitored. In the event of continuous rain or nighttime temperature drops, moisture absorption and mold growth are prone to occur. Mechanical drying saves time and effort and is not affected by the weather. However, the equipment, energy consumption and maintenance are real costs. Larger-scale growers or cooperatives usually choose to build drying centers or purchase services to handle moisture quickly; while small-scale farmers still prefer to dry in the sun or leave the crops in the shed to dry (Zhao et al., 2020). Additionally, due to different subsidy policies and service conditions, the judgment also changes accordingly. In the end, it is a balancing act between the amount of money spent, the speed of work and the quality of the product. 3 Effects of Drying Methods on the Physical Quality of Rice 3.1 Characteristics of moisture content changes and comparison of stability In the end, drying is judged by how quickly and steadily the moisture content decreases (Yang et al., 2019). By comparing, it can be found that during mechanical drying, the moisture content decreases relatively evenly, with a smooth curve change, and the external environment has little impact on it. Natural drying is not as "obedient", as the temperature, humidity, and sunlight change, the moisture content also fluctuates accordingly. For two samples with moisture contents of 24.4% and 18.7%, the mechanical drying side basically shows a steady decrease; while the drying group experienced rehumidification during nighttime cooling or rainfall, and the data fluctuated significantly (Phanphanich and Mani, 2017). When hot air is continuously supplied, the drying rhythm is relatively controllable, but for natural drying, it needs to rely on frequent turning over and timely rain protection to compensate for the interference caused by the weather; otherwise, the efficiency and stability cannot be guaranteed. 3.2 Analysis of the differences between whole-grain rice rate and broken rice rate When evaluating the drying effect, the whole-grain rice rate is often the most intuitive (Siebenmorgen et al., 2014). After controlling the final moisture content at the same level in the experiment, the differences between the two methods became apparent. For example, for rice with an initial moisture content of 32.6%, the whole-grain rice rate after mechanical drying could reach 85.6%, while that after sun-drying was only 72.2%, and the broken rice was significantly more. The same is true for the burst-waist phenomenon. Under high moisture conditions, the burst-waist rate after sun-drying was close to 11%, while that after mechanical drying was only about 5%; at a moisture content of 24.4%, the burst-waist rate after sun-drying was still around 3%, while that after mechanical drying was less than 1% (Figure 2) (Liao et al., 2020). This difference is mostly related to whether the drying process is stable. The temperature in mechanical drying is controlled, and
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