B. Impact of the Sorghum Market Channel on Quality
While the U.S. sorghum industry strives to minimize changes in the physical and sanitary quality attributes as sorghum moves from the farm to export, there are points in the system where quality changes inevitably occur due to the biological nature of the grain. The following sections provide some insight on the reasons sorghum quality may change as sorghum moves from the field to the railcar or ocean vessel.
1. Drying and Conditioning
Farmers try to harvest sorghum with low moisture content, which may be less than 16%. Since these levels are close to sorghum’s safe storage levels, which are usually about 13 to 14%, only minimal amounts of drying and conditioning are generally necessary for sorghum to be safe for storage and transport. Conditioning involves the use of aeration fans to control both temperature and moisture, which are important to monitor for storage stability. Drying and conditioning may occur either on a farm or at a commercial facility. When sorghum is dried, it can be dried by systems using natural air, low-temperature, or high-temperature drying methods. However, high-temperature drying is utilized far less with sorghum than with corn.
2. Storage and Handling
In the United States, sorghum storage structures can be broadly categorized as upright metal bins, concrete silos, flat storage inside buildings, or flat storage in on-ground piles. Upright bins and concrete silos with fully perforated floors or in-floor ducts are the most easily managed storage types because they allow aeration with uniform airflow through the grain. Flat storage can be used for short-term storage, which occurs most often when sorghum production is higher than normal and surplus storage is needed. However, it is more diffcult to install adequate aeration ducts in flat types of storage, and they often do not provide uniform aeration. In addition, on-ground piles are sometimes not covered and may be subjected to weather elements that can result in mold damage.
Handling equipment can involve vertical conveying by bucket elevators, as well as horizontal conveying, usually by belt or en-masse conveyors. Regardless of how the sorghum is handled, some sorghum breakage will occur. The rate of breakage will vary by types of equipment used, severity of the grain impacts, grain temperature and moisture content, and by sorghum quality factors such as kernel hardness. As breakage levels increase, more broken pieces of sorghum are created, which leads to less uniformity in aeration and ultimately to higher risk for fungal invasion and insect infestation.
3. Cleaning
Cleaning sorghum involves scalping or removing large non-sorghum material and sieving to remove small, shriveled kernels, broken pieces of kernels, and fine materials. This process reduces the amount of broken kernels and foreign material found in the sorghum. The potential for breakage and initial percentages of broken kernels, along with the desired grade factor, dictate the amount of cleaning needed to meet contract specifcations. Cleaning can occur at any stage of the market channel.
4. Transporting Sorghum
The U.S. grain transportation system is arguably one of the most effcient in the world. It begins with farmers transporting their grain from the field to on-farm storage or local grain and river elevators using either large wagons or trucks. Sorghum is then transported by truck, rail or barge to its next destination. Once at export facilities, sorghum is loaded onto ocean-going vessels or railcars. As a result of this complex yet flexible marketing system, sorghum may be loaded and unloaded several times, increasing its susceptibility to broken kernels and breakage.
Sorghum quality changes during shipment in much the same manner as it changes during storage. Causes of these changes include moisture variability (non-uniformity) and moisture migration due to temperature differences, high humidities and air temperatures, fungal invasion, and insect infestation. However, there are some factors affecting grain transportation that make quality control during transport more diffcult than in fxed storage facilities. First, few modes of transport are equipped with aeration; consequently, corrective actions for heating and moisture migration cannot take place during transport. Another factor is the accumulation of fine material (spout-lines) beneath the loading spout when loading railcars, barges and ocean vessels. This results in whole kernels tending to roll to the outer sides, while fine material segregates in the center. A similar segregation occurs during the unloading process at each step along the way to final destination.
5. Implications on Quality
The intrinsic quality attributes such as protein cannot be altered within a sorghum kernel. However, as sorghum moves through the U.S. sorghum market channel, sorghum from multiple sources is mixed together. As a result, the average for a given intrinsic quality characteristic is affected by the quality levels of the sorghum from the multiple sources. The above-described marketing and transportation activities inevitably alter the various physical and sanitary quality characteristics. The quality characteristics that can be directly affected include test weight, damaged kernels, broken kernels, kernel size, moisture contents and variability, foreign material, and mycotoxin levels.