Submitted to: Stored Products Protection International Working Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 10/20/2003
Publication Date: 12/1/2003
Citation: Dorner, J.W. 2003. Stack-curing and storage of peanuts for prevention of postharvest aflatoxin contamination. Stored Products Protection International Working Conference Proceedings. CAB International, Cambridge, MA. pp. 539-545.
Interpretive Summary: Aflatoxin contamination of peanuts is a serious problem wherever peanuts are grown. Contamination can occur while peanuts are maturing on plants (preharvest) or after they have been harvested and during storage (postharvest). Postharvest contamination is a particular problem in parts of the world where facilities are not adequate to properly dry harvested peanuts and maintain peanuts at a safe storage moisture content. A study was conducted to determine the potential for aflatoxin contamination of peanuts that are slow-cured in stacks, a method of curing peanuts that was widely used in the United States during the early to mid-1900's. This method involves placing poles into the ground that have two cross-pieces about a foot above ground level. Harvested peanut plants are placed on the cross-pieces and wound around the pole with pods facing the pole and foliage facing outward. The finished "stack" has the pods near the center where they are protected from the weather by the vines. In this study eight stacks were constructed for each of two digging dates in south Georgia. Half of the stacks received supplemental irrigation to mimic curing conditions that might normally be experienced in humid, tropical areas of the world where postharvest aflatoxin problems are greatest. Results showed that the only significant aflatoxin formed in stacks from the first harvest (when ambient temperatures were higher) that received supplemental irrigation. Although irrigated stacks from the second harvest received abundant rainfall and supplemental irrigation, they were not contaminated. Results overall indicate that stack-curing of peanuts may be a better way to cure and store peanuts in parts of the world where postharvest aflatoxin contamination is still a serious problem. Further investigations in those specific areas are warranted.
Technical Abstract: Postharvest aflatoxin contamination of peanuts is a serious problem around the world. In many areas, the lack of mechanized drying of harvested peanuts and lack of adequate storage facilities to maintain proper moisture conditions facilitate the growth of Aspergillus flavus and A. parasiticus and the contamination of peanuts with aflatoxins. In the early to mid-1900's in the USA, peanuts were cured by constructing "stackpoles" around which freshly dug peanut plants were "stacked" off the ground. Peanut pods were in the center near the pole and plant material and foliage faced outward. Studies have been carried out to determine the potential for aflatoxin contamination of peanuts cured in stacks. Peanuts were dug at optimum maturity in south Georgia at two different times and were cured conventionally (windrow curing followed by artificial drying) as well as in stacks. Half of the stacks received substantial supplemental irrigations in addition to natural rainfall to create the worst possible curing and storage conditions. Conventionally cured peanuts were harvested after windrow curing for three days, and stacks were harvested after a curing period of about six weeks. All peanuts were evaluated for A. flavus growth and aflatoxin contamination. Results from the first harvest showed that significant (P 0.05) aflatoxin (mean = 118 ppb) formed only in stacks receiving supplemental irrigation (49.5 cm of combined rainfall and irrigation). Stacks from the first harvest, which were not watered, received 14.2 cm of rainfall, but contained only 2.6 ppb of aflatoxin. Conventionally harvested peanuts were not contaminated. No peanuts were contaminated with aflatoxins from the second harvest even though the irrigated stacks received 53.8 cm of rainfall and supplemental irrigation.