Research On The Deterioration Of Rice Post-drying Quality With Vacuum Drying

Drying is necessary to rice processing and storage after post-harvest, directly affecting its edible value and commercial value of rice. Drying quality was researched with constant temperature and variable temperature drying by vacuum and tempering was researched. Main conclusions are as follows:(1)According to different vacuum drying condition, rice drying curves and drying rate curves were drawn under different condition of constant temperature and variable temperature vacuum drying. While the vacuum drying temperature, vacuum degree, the initial moisture content is higher, the rice drying rate is greater; the shorter drying time is needed for safe water. While compared to constant temperature drying, variable temperature can improve the rate significantly.(2)The effect of constant temperature vacuum drying on the quality of rough rice:the fissuring rates and the fatty acid value of paddy increased with the increase of relative vacuum. The correlation analysis showed that the fissuring rate showed a highly significantly positive correlation with both of the fatty acid value and the amylase content. The crack rate showed a significantly positive correlation with their hardness, adhesiveness and gumminess of cooked rice; and the head rice rate had a significantly negative correlation with their hardness, adhesiveness and gumminess of cooked rice. The results of the SEM showed that the degree of binding of starch granules and protein structure was sloppier, drying cracks was thicker, the number was larger with the higher drying temperature, the greater the relative degree of vacuum and the higher the drying rate.(3)Drying temperature, temperature drying rate and their interaction on rice blast waist, whole polished rice rate, and fatty acid values has a significant impact, influence the roughness of rice was not significant; the tempering can obviously reduce critical waist rate, fatty acid value of rice, increase the rate of the whole white rice. Variable temperature-drying methods on the retro gradation of rice gelatinization value, minimum viscosity influence significantly; tempering affect significantly for the retro gradation of rice gelatinization value. Using membership degree comprehensive evaluation method of variable temperature drying rice quality index comprehensive evaluation after, when from high to low temperatures and cooling dry, appropriately increase the temperature difference, after working on rice quality more favorable; When gradually from low to high temperature heating drying, appropriate to reduce the temperature difference, can better ensure the quality of rice after dry.