Study On Mechanism And Model Of Microbial Field And Multi-Fields Interaction In Grain Bulk

Grain safety plays an essential role in food security.During the process of storage,grain would certainly be affected by various physical and biological factors.And microorganisms in storage ecosystem would seriously affect the grain quality,then threaten its safety.Although people have done a lot of research on grain storage.The following problems still exist:(1)to study single factor changes,ignoring interactions among factors in grain bulk ecosystem;(2)to study physical factors change,ignoring impact of biological factors on grain bulk ecosystem;(3)Biological effects were mostly laboratory research,while field effects were rarely being studied.In order to solve the above problems,this paper introduced and defined a concept of grain microbial field,revealed the microbial field effect,established microbial field model,and analyzed grain bulk data in squat silos to verify the model.Finally,the grain microbial field theory was applied to grain storage safety management and control.The research relied on project of Research on the Application of Multi-Field Coupling Model Regulation and Regional Standardization for Grain Bulk which was a special fund for grain-scientific research in the public interest in 2015.The research contents and results were as follows:(1)The concept of microbial field in grain bulk was defined,and the changing law of microbial field was summarized.Field varies spatially and temporally.In grain bulk ecosystem,grain microorganisms change over time and space,and affect biological and abiotic entities in surrounding environment at the same time.Therefore,we proposed a definition of biological field:a biological field was the spatiotemporal distribution of a biological entity,with the ability of influencing the surrounding biotic and abiotic entities.In grain bulk ecosystem,microbial field interacts with other biological and physical fields,which could be depicted as week interaction,strong interaction and losing interaction.According to the strength of field effect,the succession process of grain microbial field could be divided into four stages:dormant stage,latent stage,self-excitation stage and decay stage.(2)A formula for calculating microbial field strength in grain bulk was established in this paper.In the stored grain ecosystem,fungi decomposes nutrients(carbohydrates,fats,proteins,etc.)to grow,and heat is produced.We can use the heat production of carbohydrate decomposition(the dominant fungal activity in stored grain)to illustrate how to quantitatively determine the strength of a biological field.The energy of grain microbial field was equal to heat produced by stored microorganisms metabolism,then field strength of microbial field was heat production by stored grain microorganisms in unit time and space.(3)The microbial field effect and calculation formula of grain bulk were verified by experiments.In the experimental study of induced,spontaneous,gradient temperature field and microbial field in warehouse,temporal and spatial changes of microbial field and field strength were calculated,and microbial field effect and calculation formula were verified.The microbial field experiments under induced and spontaneous conditions showed that microbial field in grain bulk varied spatially and temporally,and heat and moisture produced by microbial field had a strong impact on biological and abiotic entities,especially in upper grain bulk.Taking the gradient temperature field test and microbial field test which was carried out in a warehouse as examples,microbial field strength was calculated and microbial field calculation formula was proved.At the same time,temperature field could be expressed as a cubic polynomial of temperature difference in coupling process of microbial field with other physical and biological fields.Moreover,changes of grain microbial field could be predicted by quantifying the number of fungal spores.(4)The microbial field theory guided safety management and control during grain storage.Coupling and decoupling grain storage management and control methods based on microbial field and multi-fields interaction theory were preliminarily explored.According to formula of microbial field strength,heat absorbed by both large and small hot spots in corn grain bulk of squat silo was calculated.Comparing the heat absorbed by grain bulk with the heat taken out of the squat silo by ventilating,it was found that the heat(2.87×10~5kJ)taken out of the squat by aeration was higher than that absorbed by the small hot spot(1.98×10~5kJ),but lower than the maximum absorbed heat(1.00×10~7kJ)of the large hotspot.In this way,the microbial field of small hot spot appeared decoupling,but the large one was still in the self-excitation state.The heat taken out of the squat silo by chiller was 1.45×10~7kJ,higher than that absorbed by the large hot spot(1.00×10~7kJ).Therefore,decoupling of microbial fields in large hot spot had appeared.This study proved that decoupling energy in a certain time must be higher than the maximum energy of microbial field in grain bulk to achieve decoupling effect.The coupling effect of microbial field and physical field in grain bulk ecosystem was studied by grain microbial field theory,and two-dimensional and three-dimensional research of stored grain microorganisms were realized.This provided a solid theoretical basis for eliminating hidden mould danger in the storage process,and it was critical to realize safety management and control for automatic grain storage.