Research Of Early Mildew Point Location In Stored Grain By CO₂ Monitoring Method

This report mainly discusses the diffusion regulation of CO2 gas produced by the mildew grain in grain piles and the effects of different conditions on the CO2 gas concentration, with these results, we can locate the sites of mildew grain by the change of the CO2 concentration detected in stored grain. And the results will provide effective guidance for spoilage accurate processing in the large-scale grain storage.The diffusion regularity of CO2 gas produced by simulate mildew spot in the grain pile is studied, and the result shows that in less than 2 m, at the layer of the mould, the CO2 concentration is the highest, the lower second, upper minimum. With the increase of detection distance, the attenuation speed of the upper and middle scope is significantly higher than the lower attenuation speed, and the concentration of lower layer is significantly higher than the middle and upper ones when it is more than 2m. In addition, it happens almost at the same time when the CO2 concentration near origin mildew point change significantly, however,with the enlargement of the detection distance, the time of a significant rise in gas concentration in the lower layer is obvious earlier than others, at 3 m distance, the significant changes of CO2 concentration of lower layer can be detected 3 days earlier than the middle ones, and 5 days earlier than the upper ones.Amount of mildew grain has obvious impact on CO2 concentration. Results of the research on different amount of mildew grain show that the detected concentration of CO2 near the mildew grain of 5kg can reach the maximum of 0.768%, much less than the CO2 concentration of the 10 kg and 20 kg mildew grain, which can reach the maximum of 2.423%.correlation analysis was carried out on the CO2 concentration and amount of mildew, and the result show that they are in line with the exponential function, and the correlation coefficient can reach 0.99. the increase of CO2 concentration nearby 20 kg of mildew grain can be0.689% in the period of significantly change, however, it is only 0.161% when the amount of mildew grain is 10 kg, a quarter of the former.Depth of mildew point in grain bulk also has an obvious influence on the concentrationof the CO2 gases. The results of experimental on the same mildew grain which are in different depth show that the CO2 concentration can reach 2.063% when the mildew points ’s depth is1 m, however, it is 2.731% when the depth is 3m. Moreover, the embedding depth of mildew point also has an obvious influence on detecting range of CO2 gas. Detecting range of the CO2 from 1m depth mildew points is 1.5m, however, it is 2.3m when the detecting depth is 3m.The position of mildew point in grain bulk can be accurately determined through the analysis of different detecting results in grain bulk. Data analysis on CO2 concentration of different depth show that CO2 concentration of the 2m depth in the northeast corner is obvious higher than others, and the concentration of 3m depth is higher when it is 4m far, which shows the depth of mildew point may be 2m. Analysis of the data in 2m depth shows that CO2 concentration of three detecting point in the northeast change significantly(p<0.05). With the detecting data of 0.542%、0.151%、0.145% and the distance of 4m between each other, we can determine the space location of mildew grain. Result shows that mildew point is 0.84 m far from the eastern border, and 0.87 m far from the western border. Validation of the positing result shows that the inoculum amount of theoretical simulation of mildew point is 4.6 x 106cfu/g, far above the normal amount of 1 x 103 cfu/g, which proves the accuracy of positioning results. The amount of error between theoretical result and the actual result is 0.2m, which means a higher accuracy of positioning result.