Effect On The Quality Of Tempering On Microwave Drying Soybeans

During the harvest season, it is difficult to maintain the safe storage moisture (<13%wet basis) for soybeans due to being affected by climate. Therefore, artificial drying has become an important process for high-moisture soybeans (18-20% wet basis). China is one of the major soybean producing countries. During the drying process, the drying rate of soybeans should not be too fast and the corresponding internal temperature should not be too high because of its thin seed coat. During the microwave drying of soybean, while the microwave has the characteristics of fast drying, but due to the impact of soybean tissue structure, microwave power can not be too large, can not play the advantages of microwave.In this paper, by adding tempering stage in high power density microwave drying soybean,fast drying, and can guarantee the drying quality.In this paper, it selects 0.6W/g power density as the research parameters whose drying rate is faster , energy consumption is lower,but the cracking ratio reaches 27%. Joining the tempering process to drying process, we research the internal temperature, moisture content,drying rate, cracking rate, withstanding extreme pressure, energy consumption and internal the organization of soybean.The results show that, addition of tempering could increase drying rate and reduce the internal temperature and burst rate of soybean. In the microwave drying soybean process,the tempering section is set at the maximum drying rate, which can effectively improve the drying rate and shorten the drying time and reduce the cracking rate. When the power density was 0.6W/g, in the drying process of the moisture content reducing from 20% to 12%, tempering section was set at after drying 30min and the drying effect was the best.Although the longer the tempering time, the lower the cracking rate, but the longer the tempering time, resulted in the increase of drying time and energy consumption. In this study, when the power density was 0.6W/g, tempering time being 30min could get the best drying effect after 30min of drying. When the drying finished, the cracking ratio of internal temperature was 52?, the cracking ratio of soybean was 4.67% and the whole energy consumption was 780kJ. Compared with 0.6W/g, the cracking ratio reduced by 82.7%.Compared with that without tempering which was 0.2W/g, the drying time reduced by 63.9% and the energy consumption reduced by 63.9%. The addition of any drying methods will change the internal structure of soybean, and the formation of water channel will disperse the original dense internal structure, which can reduce the extreme pressure.