Study On CO₂ Characteristics Produced By Insects And Moulds In Stored Grain

During grain storage, moulds and insects could cause serious harm to grain. Earlier detection of mouls and insects was the key to prevent the harm deteriortion. This report mainly studied the CO2 characteristics released by moulds and insects in stored grain under different conditions, so that we could establish a new mothed for grain monitoring and distinguish the grain storge damage of moulds and insects by using CO2.The results showed that both the moisture contents and the temperature affect the rate of CO2 released by moulds. Temperature significantly affected the CO2 rate when the grain moisture contents above the safe moisture. 10-fold of CO2 amount increased when storage temperature rose from 20 ℃ to 25 ℃. Temperature was not significantly affected the CO2 rate when the grain moisture contents under the safe moisture. CO2 rate was only 0.5mg/g.d after storage 30 d. Effect of temperature on stored grain insects has no contact with grain moisture content. Rate of CO2 released by stored grain insects increased with the temperature increase. 60% and 11% amount increased when storage temperature rose from 20 ℃ to 30 ℃. The sensitivity of the temperature changes was same between different insects.The grain moisture content significantly affected the amount of CO2 released by moulds. The safe cereals with 13% moisture content, amount of CO2 was below 10 mg with increased less than 5% after storaged 30 d.In 15% moisture content of wheat, rate of CO2 increased 15.6 times in 9 d with increasing the 2% moisture content of wheat. The moisture content of grain has no significant effect the CO2 amount released by maize weevil and other insects(p>0.05), the moisture content of wheat above the basic need of insect has little cntribution on CO2 production.The species of moulds significantly affectd the amount of CO2 released by moulds. The same number of A.flavus produced more CO2 than Penicillium. In 15% moisture content of wheat, gas production of A.flavus was 2.5 times of Penicillium, this difference was exacerbated with increasing the grain moisture content.Different kinds of insects also produced different CO2 amount. Tribolium castaneum produced 6 times CO2 of Sitophilus zeamais. Sitophilus oryzae and Sitophilus zeamai has no significantly difference with CO2 production because of the similar size and habits.The amount of moulds and the state of moulds both affect the mildew produced CO2. The dormant moulds in safe grain produced little CO2 and has no damage to grain; The growth fungi produced more CO2 and cause greater damage to grain.The CO2 amount released by insects only related to the insect numbers, linear correlation coefficient r2>0.95.Grain varieties could affect the growth of fungal; thereby affect the amount of CO2 produced by fungi. In high moisture grain, the fungi in wheat growth 7 d earlier than in rice, the CO2 produced by wheat was 63.7% higher than rice. Grain varieties have no significantly difference to incest on CO2 production. This was the different characteristics of fungi and pests when growing in different types of grain.Adult and larval of stage of Sitophilus zeamai produced more CO2 than in pupae and eggs. These differences could be monitored by CO2 thus distinguishin the gphysiological period of Sitophilus zeamai and predicting the population of insect development in the future.Insect activity can significantly increased the amount of moulds when fungi and pests stoored together. The CO2 amount in the system was significantly higer than they storage separate. With the increase of the grain moisture, the contribution about moulds amount cause of pests’ activity was gradually reducede the diversity decreases gradually.The pattern obtained from laboratory was the same good applicability in grain warehouse, the correlation coefficient was larger than 0.95. This reseatch has contribute to development a grain safety storge system based on CO2 monitoring, and laid a data base on determine the biologica speices, population and the damage extent. CO2 monitoring technology may be possible to apply to reduce grain losses, ensure grain security in grain storage in the future.