Studies On The Dring Characteristics Of Rice Fluidized Bed Drying And Effects On Its Quality After Drying

As China's grain output continuously growing for the last twelve years,the annual gain output pressure even huger,timely drying the newly-harvested paddy rice with high moisture content is particularly necessary.This paper studies the fluidized bed drying-tempering process of paddy rice,analysising quality change rules of paddy rice after the fluidized bed drying-tempering method.Using responsing surface analysis to obtain the optimal parameters of fluidized bed drying,and exploring the quick nondestructive testing technology on the water content of paddy rice which using low field nuclear magnetic resonance technique.The main conclusions are as follows:1.Mathematical simulation of fluidized bed paddy drying characteristic curves under different initial moisture content and different drying temperature,comparing the models,page model was the best fittinged model.In the same drying temperature,higher initial moisture content of paddy rice,longer time needed to get to the safe moisture content.Under the same initial moisture content,drying temperature increase,shorter time needed to get to the safe moisture,and drying rate increased.2.Effect of the fluidized bed drying conditions on the quality of paddy rice: The moisture removal of each drying pass(MREDP),air temperature and the tempering time have a significant influenc on the additional crackle ratio increment(ACRI),amylose content,peak viscosity,breakdown viscosity,and setback viscosity of the rice(p<0.05).With the MREDP increasing,increased the ACRI and the setback viscosity,decreased the amylose content,peak viscosity and breakdown viscosity;With the drying temperature increasing,ACRI,a value,amylose content and setback viscosity increases gradually,while the b value,peak viscosity and the breakdown viscosity decreaseing;With the tempering time increased,decreased the ACRI,L value,amylose content and setback viscosity,but increased a value,peak viscosity,breakdown viscosity;With shorter tempering time,higher air temperature and larger MREDP,the microstructure of the rice grain changes which including the starch granule's arrangement become loosener,the gap between starch grains become larger,local crack become deeper.3.ACRI of the rice under fluidized bed drying was extremely significant positive correlated with amylose content,setback viscosity,but extremely significant negative correlated with peak viscosity,breakdown viscosity;The surface color L value and b value was extremely significant positive correlated;a value and b value breakdown viscosity have an extremely significant positive correlation,but significant negative correlated with amylose content;b value and amylose content was extremely significant negative correlated;amylose content and breakdown viscosity was extremely significant negative correlated;the peak viscosity and breakdown viscosity showed a significant positive correlation.But with the setback viscosity was extremely significant negative correlated;the breakdown viscosity and setback viscosity was extremely significant negative correlated.4.In order to optimize the fluidized bed drying process of paddy rice,the BoxBenhnken response surface experimental design of three factors and three levels were used to analysising.The results showed that the drying efficiency,the additional crackle ratio increment,the chalky kernel ratio and hardness of paddy rice increased with the increasing of the temperature of drying air and the moisture removal of each drying pass,while the fatty acid value and adhesiveness decreased.However,the ACRI,FAV and hardness decreased and the adhesiveness of rice increased when the tempering time increased.The membership degree comprehensive rating scores achieved highest under the optimum drying condition,which were the air temperature of 60 ?,the MREDP of 2.50%(dry basis)and the tempering time of 3 h,.It has been proved that the results were reliable and effective since the experimental data and the simulated value with no significant differences(p>0.05).5.There is an obviously positive linear relationship between the moisture content and the NMR relaxation spectrum of T21 peak area,peak area of T22 and the T2 peak area.The fitting equation of moisture content and T21 peak area: y=0.00005x-0.0572(R2=0.9812).With LSD multiple comparison,it is concluded that the difference between the two methods of 105 degrees oven drying method and magnetic resonance method is not significant(p>0.05).The higher moisture content of the rice,the more clear the nuclear magnetic image.The linear relationship between the gray value and the moisture content is fitted.With the moisture content of rice increasing,the gray value of NMR image reducing.The linear equation of moisture content(x)and NMR image gray value(y)is: y=-0.2286x+11.204.(R~2=0.9259).