Effect Of γ-ray Irradiation On Drying Characteristics And Qualities Of Rice And Wheat

There are deficiencies when grain dried with traditional hot-air method, such as low drying efficiency, inferior qualities, and so on, It is found that, besides sterilization, γ irradiation can increasing the water activity and accelerate the diffusion of water during drying. However, the effects of drying after y irradiation pretreatment on the qualities of agriculture product are less studied. In this thesis, irradiation dose, drying temperature and initial moisture content, significantly affecting on the drying characteristics and processing, eating and seed qualities of rice and wheat, are selected as the experimental factors throughout the paper. Single factor analysis and multianalysis are employed to investigate the effect of three factors on drying characteristics, processing, eating and seed quality. Besides, experimental result are analysed from microstructure, physicochemical properties.1. Effect of irradiation on drying characteristics of rice and wheat.1) Three effects (irradiation dose, drying characteristics, initial moisture content) can affect the microstructure, water activity and calorifics properties of rice and wheat. These effects can change the drying characteristics and surface temperature of rice and wheat significantly.2) Basing on the single factor analysis and multianalysis, three factors can significant affect the drying time and mean dehydration rate, and second-degree polynomial models are founded. These models can effectively forecast the effect of three factors on drying time and mean dehydration rate.3) According experiments, the irradiation dose can affect the equilibrium moisture content and moisture diffusion coefficient of hot-air drying significantly. New adsorption-desorption models of equilibrium moisture content and moisture diffusion coefficient are established based on the traditional models.4) Base on the traditional semi-experiential drying models, better models affected by three factors are founded and the coefficients are fitted.2. Effect of irradiation on processing and eating quality of rice and wheat.1) According experiments and analysis, irradiation dose has no significant effect on processing quality of rice due to the disorganization making the tissue more compact when shrinking during drying, and this counteract the effect of disorganization. Drying temperature and initial moisture content have significant effect on processing quality, and this because different temperature grads and moisture grads formed in different temperature and initial moisture content, and these cause different degree of weeny crack for different internal stress. Besides, three factors have no significant relative with the processing quality of wheat. It is because that the processing quality of wheat can not be affected by the destroy of internal tissue and the weeny crack.2) Basing on the microstructure observation and theory analysis, gamma irradiation can destroy the large molecule including starch, protein and fat significantly. The activity of hydrolyse enzyme is differed when drying temperature and initial moisture content changed. Three factors all have significant relative with the indexes of eating quality of rice and wheat.3) Basing on the single factor analysis and multianalysis, three factors affect the apparent amylosecontent, gel consistency, gelatinisation temperature, wet-gluten content, gluten water holding rate, and value of fatty acid significant and second-degree polynomial models are founded. These models can effectively forecast the effect of three factors on the indexes of eating quality of rice and wheat.4) Viscosity properties is relative with the structure of starch of rice and wheat closely, basing on the viscosity experiments, the viscosity indexes are all affected by three factors significantly. 2. Effect of irradiation on seed quality of rice and wheat.1) Basing on the microstructure observation and theory analysis, gamma irradiation and drying temperature can destroy the embryo of rice and wheat. The irradiation dose and drying temperature have significant relative with the short-term germination characteristics of rice and wheat. And the irradiation dose has significant relative with the long-term germination characteristics of rice and wheat due to the self-repair ability of rice and wheat and the their respiration during storage. Besides, the irradiation dose and drying temperature have significant relative with the short-term and long-term activity characteristics of rice and wheat also due to the conjunct effect of destroy of embryo, the self-repair ability of rice and wheat and the their respiration during storage.2) The irradiation dose and drying temperature have significant relative with the microorganism content due to the destroy of gamma irradiation on organism cell and restraining growth of microorganism caused by high temperature. The initial moisture content affects the total microorganism content significantly and cannot affect the detect rate of mildew due to the different physiology properties belonged to different microorganisms have. For the same reason, content of different microorganisms show different changes during storage.