Skip to main content
ARS Home » Southeast Area » Dawson, Georgia » National Peanut Research Laboratory » Research » Publications at this Location » Publication #324495

Research Project: Postharvest Systems to Assess and Preserve Peanut Quality and Safety

Location: National Peanut Research Laboratory

Title: Storing Peanuts in Grain Bags

item Butts, Christopher - Chris
item WARD, JASON - Mississippi State University

Submitted to: Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE)
Publication Type: Proceedings
Publication Acceptance Date: 1/1/2016
Publication Date: 7/11/2016
Citation: Butts, C.L., Ward, J.K. 2016. Storing Peanuts in Grain Bags. Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE). doi:10.13031/ids.202456481.

Interpretive Summary: Farmers stock and shelled oil stock peanuts were loaded into grain storage bags and stored for 60 days from May to July 2015. The 90 tons of in-shell farmers stock peanuts were taken out of conventional bulk storage at approximately 6% moisture content and loaded into two grain bags. The peanuts were unloaded from hopper bottom trailers into a grain cart, then unloaded from the grain cart into a gravity flow bag loader. The gravity flow bag loader is basically a hopper that has the grain bag attached to a horizontal outlet, and as the peanuts flow out of the hopper and into the 9-ft diameter grain bag, and slowly pushes the bag loader forward. In the same fashion, two grain bags were filled with shelled oil stock from a commercial oil mill. Sensors to measure temperature and relative humidity inside each of the bags were installed and readings recorded every 4 hours. A probe was inserted into each bag on a weekly basis, and a handheld meter was used to monitor the oxygen levels in each bag. After 30-days, one of the farmer stock bags was unloaded using a grain vacuum. Then after 60 days, the remaining farmers stock bag and the two oil stock bags were unloaded. The gravity feed bag loader fllled the bag bags as designed. The two farmers stock bags each held 51 and 48 tons of farmer stock peanuts and required 2.75 and 2.25 ft/ton respectively. Each oil stock bag held 47 t each and required 1.3 ft/ton. The oxygen levels in the two farmer stock bags decreased from an ambient concentration of 21% to 9% in 15 days. After 20 d storage, the oxygen level in the oil stock decreased and stabilized at 14%. The grain vac performed very well when unloading the first farmers stock bag. When the bag was opened, very wet , moldy, and musty smelling peanuts were discovered in the top of the bag for the entire length of the bag. Using the vacuum, we unloaded the wet moldy peanuts into a peanut trailer, the dried them before grading. We then used the vacuum, to unload the remainder of the bag into hopper bottom semi-trailers. Due to the mold, the peanuts were transported directly to the oil mill for shelling and use as feedstock for the oil expeller instead of entering the edible trade. The vacuum extractor clogged due to poor adjustment by the operators when unloading the second farmers stock bag, and so the bag was unloaded using a skid-steer loader. We tried to use a conventional bag unloader to unload the grain bags with oil stock. The grain bag is opened on the end and fed onto a roller on the bagger. Two small augers, pull the material from the edges of the bag into a central auger that moves the material flowing into into the small transfer augers into a waiting trailer. As the material flows out, a roller rolls up the empty bag, much like a toothpaste tube is rolled up as it is emptied. However, the oilstock peanuts clumped together and did not flow into the transfer augers, causing too much tension on the grain bag, and caused the grain bag to tear. A skid steer loader was used to complete the unloading process. Because the farmers stock peanuts were used as feedstock for the oil mill instead of edible peanuts as originally intended, their value decreased 66% as a result of the storage from $432/ton to $125/ton, making storing farmers stock peanuts in grain bags an unsuitable alternative storage method. No condensation or moisture problems were observed in the oil stock peanuts. However, before oil stock is stored in grain bags, unloading equipment needs to be modified or developed for material with poor flow characteristics.

Technical Abstract: A study was executed to determine the potential of storing farmers stock peanuts and shelled peanuts for crushing in hermetically sealed grain bags. The objectives of the study were to evaluate equipment for loading and unloading the grain bags, the capacity of the grain bags, and the changes in quality. In May 2015, approximately 90 t of farmers stock peanuts from the 2014 crop were unloaded from a commercial warehouse, transported to Dawson, GA and loaded into two 2.7-m diameter grain bags. Similarly, 85 t of shelled oil stock peanuts from a commercial oil crushing facility in Dawson, GA were loaded into two 2.7-m diameter grain bags. Peanuts were unloaded from the hopper truck into a grain cart, then into a gravity flow bag loader. After a 30-d storage trial, one farmers stock storage bag was unloaded on 10 Jun 2015. After 60 d in storage, the remaining farmers stock and both oil stock bags were unloaded on 07 Jul 2015. Temperature and relative humidity sensors were installed in each bag and monitored throughout the storage period. Oxygen levels were measured periodically using a handheld oxygen analyzer. Oxygen content in the farmers stock peanuts decreased from ambient levels (21%) to an average of 8.6% after 15 d is storage. After 20 d storage, the oxygen content in the oil stock had decreased to 14%. A vacuum extractor was used successfully to unload one farmers stock bag. Due to improper adjustments on the vacuum extractor, a skid steer loader was used to unload the second farmers stock bag. An attempt was made to to unload the oil stock bags using a conventional bag extractor, but the poor flow characteristics of the oil stock peanuts caused the bag to tear and a skid steer loader was used to complete the process. Moisture migration and subsequent condensation caused considerable mold in the top of both of the farmers stock bags resulting in the peanuts being unsuitable for human consumption and reducing the value from $342/t to approximately $125/t for oil stock, a 63% reduction in value. No mold was observed in the oil stock bags when they were unloaded. Based on these studies, sealed grain bags would be unsuitable for storing farmers stock peanuts. Sealed grain bags could possibly be used to store oil stock peanuts for 60 d, but suitable unloading equipment would have to be found or developed.