| In recent years, during the storage and drying operations, grain damage problem is outstanding, which causes the vast waste and quality decline of cereal, and seriously restricts the development of grain industry in China. Based on the moisture adsorption and desorption theory and glass transition theory, this paper took Long yang, Zhun liang you, Dian jiang and Zhong jia zao the four rough rice varieties as the main research material, and ultilzed fissure ratio, fissure index and biological staining method to quantify and detection the fissures and research the change laws of hygroscopic expansion coefficient and the glass transition temperature the two thermal physical parameters in the process of storage and drying respectively of rough rice and their influences on fissure formation and propagation of rough riceThe main research contents and results as follows:1. The change laws of length, width and volume along with the moisture content of the single kernel of rough rice and brown rice law after adsorption and desorption equilibrium were studied, and the linear hygroscopic expansion coefficient and volume hygroscopic expansion were calculated and their change laws were analysed.The results showed that the length, width and volume of the sample kernels were linearly correlated with their moisture content after equilibrium, when the moisture content is higher the length, width and volume of single kernels were greater, conversely, they were smaller. The linear correlation of the length and moisture content of sample kernels after equilibrium was the best, then the linear correlation of the width, the linear correlation of the volume and moisture content was the worst. Compared to rough rice, the linear correlation of length, width and volume and moisture content of brown rice after equilibrium was better. The linear correlation of the volume and moisture content of samples of normal moisture content after equilibrium was better than that of samples of high moisture content. The hygroscopic expansion coefficient of brown rice is greater than that of rough rice in the same species.2. The fissures on rough rice and brown rice samples were observed through the light box method after adsorption and desorption equilibrium, and analysed qualitatively and quantitatively by fissure ratio and fissure index. The function relationship was established between the fissures and equilibrium moisture content, and the causes of crack formation and propagation were explained from the theoretical perspective of moisture adsorption and desorption and hygroscopic expansion. The results showed that when the moisture content of rough rice and brown rice of high moisture content was higher after equilibrium, the fissure ratio was lower, but when the moisture content of rough rice and brown rice of normal moisture content was closer to the moisture content before sample introduction, the fissure ratio was lower after equilibrium. When the moisture content of rough rice and brown rice of high moisture content was higher after equilibrium, the chap ratio was lower, but when the moisture content of rough rice and brown rice of normal moisture content was closer to the moisture content before sample introduction, the chap ratio was lower after equilibrium. The double fissures ratio of Long yang brown rice of normal and high moisture content and Zhun liang you rough rice of normal moisture content, The single fissure ratio of Zhun liang you brown rice and rough rice of normal moisture content were mainly accorded with the change trend above.3. To explore between the glass transition temperature and moisture content of rough rice, the glass transition temperature of rough rice with different moisture content was measured by using differential scanning calorimeter. And corresponding regression equations of their function relationship were fitted, the change rules of the moisture content and glass transition temperature were analyzed. The results showed that the glass transition temperature gradually reduced with the increase wet basis moisture content of rough rice. In drying process of Zhun liang you and Dian jiang the two rough rice, the drying temperature could be controlled under 39 ℃ to dry continuously. Also, the method of variable temperature drying could be adopted, the drying temperature should be always lower than the glass transition temperature of current moisture content, and the rough rice was always kept at the glassy state. Those methods could effectively inhibit the generation of fissures, and guarantee the head rice yield. In different thin layer drying temperatures, the glass transition temperature of rough rice was different under the same moisture content. The lowest glass transition temperature of Zhun liang you rough rice during drying is at the temperature of 55 ℃, the highest glass transition temperature during drying is at the temperature of 65 ℃. The lowest glass transition temperature of Dian Jiang rough rice during drying is at the temperature of 60 ℃, the highest glass transition temperature during drying is at the temperature of 70 ℃. The best fitting equation of function relationship curve between glass transition temperature and moisture content of Zhun liang you and Dian jiang rough rice is linear equation and power equation respectively.4. The change laws of thin layer drying curve and the function relationship between rough rice moisture content and supernate absorbance value after elution were obtained and by using fast green FCF staining method to conduct staining experiment for rough rice shelled by hand after thin layer drying. The absorbance value and fissures were linked to explain the relationship between moisture content and fissures. The mechanism of drying fissure formation and propagation was explained from the perspective of glass transition. The results showed that, at the same time, when drying temperature was lower, the moisture content of rough rice was higher as a whole. The function relation of moisture content and drying time of rough rice was accorded with exponential curve equation. The rise of drying temperature effectively shortened the needed time of achieving safe moisture content, the efficiency of drying was raised. Supernate absorbance value after elution decreased with the increase of rough rice wet basis moisture content. Rough rice absorbance value enlarged with the increase of the rate of fissure and breakage. The best fitting equation of the relation curve between supernate absorbance value after elution and the moisture content of the three varieties of rough rice is power function curve equation. In the process of drying, the glass transition of three varieties of rough rice all happened and produced fissures and even breakage. Fast green FCF staining method could be used as a rapid detection and quantification method to fissures and breakage of rough rice.In this paper, the innovations include:(1) The hygroscopic expansion coefficient of rough rice and brown rice were measured and analyzed(2) The fast green FCF staining method was used for rapid detection of rough rice fissures. |
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