Management of In-bin Grain Drying and Storage Systems for Improved Grain Quality and Prevention of Mycotoxins

<p>NON-TECHNICAL SUMMARY:<br/> Effective management of grain in the entire value chain, especially during post-harvest processing, is critical to mitigate current food safety/security concerns, particularly those related to mycotoxin contamination of grain and co-products. Mycotoxins, especially aflatoxin, are known carcinogens that pose a severe health hazard to human and animal consumers of grains and co-products.Freshly-harvested, high-moisture content grain must be dried to minimize (or prevent) excessive respiration and mold growth on grains. At present, most on-farm systems which use either natural air or slightly-heated air to dry grain are becoming very popular. With these systems, the grain could be dried more slowly which generally results in improved quality and also the drying practice reduces pressure on commercial driers. Although drying practice with on-farm
systems can lead to very positive results, they are weather dependent and unfortunately could lead to over drying of grain, fissured kernels that reduce milling yields, result in loss of functional performance, nutritional and sensorial quality of the grain and even development of harmful molds in areas of the bin that incur delays prior to drying. In particular, the development of mycotoxin-producing mold leading to mycotoxin contamination of stored grain in the on-farm systems has become a great concern to the grain industry.Recently-introduced technology for use in on-farm drying systems offers a means to utilize the advantages of low-temperature, in-bin drying systems, yet prevent the disadvantages that are sometimes incurred. The new technology is governed by the principle of Equilibrium Moisture Content (EMC), which is the moisture content that a specific grain will attain if
exposed to air with a given relative humidity and temperature for a long enough duration. Grain dried by continuous fan operation would be exposed to multiple drying/rewetting processes due to changing hourly/daily weather, resulting in inefficient and non-uniform drying. Natural air/low temperature (NA/LT) drying with fan operation in a given EMC window restricts the delivery of air that is too wet and/or too dry. The new NA/LT in-bin technology comprises cables to monitor not only air ambient conditions, but also grain moisture content and temperature throughout the entire grain bin mass and the data can also be accessed anytime via the internet. The systems have advanced fan and heater controls or self-adapting variable heat (SAVH) capability, which automatically adjusts the upper and lower EMC windows throughout the drying process, minimizing fan run-time hours and over drying costs,
as well as moisture content non-uniformity.These new in-bin systems are becoming very popular and have great potential for wider adoption by many farmers. However, the duration required to achieve drying with the new systems is greatly affected by prevailing weather conditions (temperature and relative humidity). The real problem is that the weather may not allow drying of the grain, particularly the upper layers, in a timely manner. When this happens, there is a great possibility for mold growth in the grain mass, with potential mycotoxin development, and grain quality related problems such as loss of grades, functional performance, nutritional and sensory value may ensue as well. For instance, across the U.S. Mid-South, prevailing weather conditions will dictate the upper moisture content limit of grains that can be stored in these new in-bin drying/storage systems without significant
"quality" deterioration and mold growth leading to mycotoxin development. The term ""quality"" could mean desirable characteristics for effective further processing and/or end-use. It is vital to know, for instance in the case of rice, how rapid grain ""quality"" attributes, such as grain yellowing, hardness, dry matter loss/respiration, milling, nutritional, functional (e.g. paste viscosity, stickiness, cohesiveness etc.) and sensory related characteristics change under prolonged high-MC conditions; and for the case of soybean destined for seed, how germination rate is impacted under different drying and storage conditions.The primary and practical questions the research will seek to answer for successful implementation of the new in-bin systems in Arkansas and the Mid-South are as follows: (1) what is the rate of grain "quality" reduction and mycotoxin development under various
drying/storage scenarios; (2) with respect to stored product ""quality"", what is the upper moisture content limit for grain (rice, corn, sorghum, and soybean) placed into these systems at various locations; (3) what energy savings could be realized with these new in-bin drying/storage systems?

<p>APPROACH: <br/>Laboratory studies will be set up to simulate conditions of temperature, relative humidity and air flow that are generally encountered in NA/LT in-bin drying/storage practices. Popularly grown grain cultivars of rice, corn, sorghum and soybean with varied moisture contents will be stored in the controlled temperature, relative humidity and airflow environment and the conditions under which drying/storage results in reduced grain quality and production of harmful mold/mycotoxins will be determined. The degradation rates of grain quality in terms of grades, nutrition, functional, and sensory values will be determined. The rates of mold development under typically encountered storage conditions will be determined and conditions which trigger mycotoxin development delineated.Accurate grain EMC information is crucial for accurate control of the newly-developed
in-bin drying technology. New EMC determination techniques will be utilized to accurately determine EMCs for specific grains grown in Arkansas, including rice, corn, soybean, and grain sorghum. Also, in order to develop better prevention strategies for mycotoxin development in the bins, a database on microbial loads on these grains at harvest will be established. The information will be crucial to accurately quantify rates of grain dry matter loss due to respiration during drying and storage. A wide spectrum of intrinsic and extrogeneous factors that could impact grain EMC and microbial load, such as grain varieties, growing locations, and growth conditions at harvest, among other agronomical cultural practices will be considered in these studies. Some past studies have used a mathematical modeling tool called The Post-Harvest Aeration and Storage Simulation Tool - Finite Difference
Method (PHAST - FDM) to predict in-bin drying and conditioning of grains. As a preliminary study, we modified the PHAST-FDM to simulate EMC-controlled and uncontrolled natural air drying of rice at four representative rice growing locations in Arkansas. Although the EMC-controlled drying strategy was found to be the best in terms of drying and fan operation costs, the findings from these simulations are yet to be validated experimentally. Such validations, which are crucial to improve predictions with the PHAST-FDM tool, will be performed in this study. More important and conspicuously missing in the preliminary modeling work and other similar studies on the use of the new NA/LT technology is consideration of grain ""quality"" aspects relevant to further processing and/or end-use application, as well as mycotoxin development. The study will determine "quality" and mold kinetics as
functions of moisture and temperature and integrate the results in the PHAST-FDM. The information is vital to establish the critical moisture content and temperature limits that would help ensure desired grain "quality" and prevent mold development while using these new in-bin drying/storage systems. Such information will be useful for limiting the intake grain moisture content and/or operating the fan accordingly, especially for representative location and harvest date combinations in the U.S. Mid-South.This research will be conducted in collaboration with OPI-integris and IntelliAir, the leading manufacturers of cabling systems used in monitoring grain temperature, relative humidity and moisture content during in-bin drying/storage. These companies, as well as other stakeholders and equipment manufacturers, have expressed strong interest to partner in this research, and to support
realization of the project objectives for multiple grains. In this study, simulation will be conducted using various fan control strategies to generate comparative results of the regimes of moisture content and fan run-times for various grains managed at different locations within Arkansas. Field studies will be done to validate models developed using laboratory studies to evaluate the implication of these new systems on the rates of grain "quality" reduction and mycotoxin development. The research partnership with the OPI-integris and IntelliAir is expected to lead to successful implementation of the recently introduced technology for in-bin grain drying/storage, especially in Arkansas and the Mid-South. The research team is also in consultation with farmers who have expressed great interest and have offered their bins equipped with the OPI-integris and/or IntelliAir cabling systems for
sampling to validate simulation and laboratory research. A continuous IR drying system equipped with catalytic infrared (CIR) emitters for drying and decontamination of grain will be built for pre-drying grain. The system will be tested for drying and decontamination of microorganisms on grain, especially the mycotoxin-producing fungi. The effectiveness of using these systems for grain pre-drying followed by natural air or slightly heated in-bin drying/storage to reduce degradation in grain quality, functional, and sensory characteristics, and growth of harmful molds will be investigated. At the same time, the feasibility of the system to achieve improved performance when IR heating is combined with pulsed UV treatment will be evaluated; Mathematical models will be developed to describe drying characteristics, kinetics of grain "quality" change, and microbial inactivation with the above
treatments for different grains.Multispectral imaging and spectroscopic techniques as well as analysis of volatile metabolites in headspace gases for detection and quantification of mycotoxin-producing fungi and associated mycotoxins will be investigated.The feasibility of using these techniques as alternative, rapid, real time and accurate methods for detection and quantification of mycotoxin-producing fungi in grain and co-products will be determined.