Study On Fissuring Law Of Rice Kernel In Drying-Tempering Process

Paddy rice is one of the important food crops in china, due to harvest seasons and regions of moisture content is quite different, such as the South in July harvested rice moisture content of 23% -27%,the North October harvested moisture content of 15% -20%,so it need to be dry in order to achieve a safe storage moisture content of 13%. However,unreasonable mechanized drying and drying process can lead to fissure or even crack in rice kernel during drying process. High fissuring rate and crack rate will affect the head rice yield(HRY) and eating taste of rice, resulting in lower economic value, so after a constant drying process,the drying rate of rice crack is an important indicator of rationality.Tempering, as an important part of grain processing, storage and circulation, has dual characteristics of saving energy consumption and improving product quality, by adding a reasonable tempering process can make the fissuring rate of rice kernel reduced.In this paper, the experiments were carried out on different temperature of hot-air drying and drying-tempering in different conditions to rice kernel. The drying characteristics of rice kernel and the law of fissuring were studied. The results showed that the drying rate of rice kernel increased with the drying temperature, the drying time was shortened while the drying time of rice kernel was decreased with the increase of drying temperature. The fissuring rate also increased, when the drying temperature of 40 ? and 45 ?, the fissuring rate increase of less than 3%. In the drying-tempering experiment, the tempering process could increase the drying rate, and restrain the fissuring rate effectively.The results showed that when 50 ? drying-5 0? tempering, the increment of fissuring rate of rice kernel was reduced to below 3%, and the drying rate was the fastest. In the low temperature drying - high temperature tempering experiments: when the process conditions of 40 ? drying - 5 5 ? tempering and 45 ? drying- 60 ? tempering, the tempering ratio selection 1:3,each time 10 min, the fissuring rate of rice kernel is less than 3%.High temperature tempering process and the longer tempering time help eliminate rice internal moisture gradient, in order to promote uniform water distribution, so as to improve the drying rate and reduce fissure.