粮仓储粮霉变CO_2法监测值主要影响因素

Effect of CO_2 method on monitoring mildew of stored grain in warehouse and its main influencing factors

利用检测粮堆二氧化碳(CO_2)浓度变化的方法对储粮霉变进行监测,但该方法为间接测定,需对影响粮堆CO_2检测值的粮堆相关因素及传感器相关参数进行全面分析。试验结果表明,不同温度下储粮中霉菌生长早期阶段的霉菌增长量均与CO_2浓度变化同步,两者相关性系数>0.99;较低的温度可使霉菌生长产气量显著降低,在霉菌生长量相当的状态下,30℃比20℃条件下测得的粮堆CO_2浓度值高4.7倍。粮食颗粒间空隙度等多种因素均可显著影响CO_2气体扩散,稻谷粮堆比小麦粮堆的孔隙度高约30%,稻谷粮堆在相距CO_2发生源50cm的监测点比小麦粮堆测得的峰值浓度高50%,峰值时间提前4d。对粮堆不同深度发生的霉变(距粮面1,2m),监测点设在粮面下3m可减少外界气体交换的影响,监测效果优于深度为1m的监测点。CO_2气体检测过程中,高的取样气流速度可显著降低检测值;对于各种规格的输气管道,适宜的检测气体取样量为管道内部理论体积的1.5倍。通过合理设定参数,CO_2法可灵敏地监测储粮霉菌活动。

The mildew of stored grain will affect the safety of food,which can be monitored by the method of detecting the change of carbon dioxide（CO_2）concentration in grain bulk.As an indirect method,it is necessary to analyze comprehensively the related factors of grain bulk and the parameters of CO_2 sensor,which cansignificantly affect the detection value.The results showed that the mould count in the initial stage of the stored grain fungi growth was synchronized with the change of CO_2 concentration at different temperatures,and the correlation coefficient was greater than 0.99.CO_2 production decreased significantly at low temperature,the CO_2 produced at 30 ℃was 4.7 times higher than that at 20 ℃in the grain bulk of similar mould count.CO_2 gas diffusion was significantly affected by grain porosity and other factors.The porosity of rice was 30% higher than that of wheat,but the peak concentration of grain pile at the monitoring point 50 cm from the source of CO_2 was 50% higher than that of wheat pile,with 4 days earlier of the peak time.The monitoring point of 3 mbelow surface of grain bulk ccould reduce the effect of external gas exchange,and the monitoring effectiveness was better than that of the monitoring point with depth of 1 mwhen mildew position at 1 mor 2 mfrom grain bulk surface.The gas flow velocity and sampling quantity should be determined in the process of gas detection,and the detection value ccould be significantly reduced when the gas flow velocity exceeded the specified flow rate,and the gas sampling volume should be 1.5 times of the theoretical volume in the pipeline.Therefore,the carbon dioxide detection method by setting parameters reasonably could sensitively monitor the activity of mould in stored grain,and this was practically valuable for high efficiency in preventing and controlling the damage of mould.