Managing Stockpiles to Reduce Aflatoxin Potential

Recent studies supported by the Almond Board of California have shown that certain conditions can lead to the growth of the aflatoxin-producing molds Aspergillus flavus and A. parasiticus and aflatoxin production in almond stockpiles.

UC researchers Bruce Lampinen and Themis Michailides began a research project in 2007 to examine temperature and moisture conditions in stockpiles, and to develop recommendations for stockpiling that will minimize the potential for growth of Aspergillus.

The researchers found that stockpiling of in-hull almonds with a total fruit (hull, shell, kernel) moisture content above 9%— 9.2% in these studies—can lead to problems, particularly on the outer areas of the piles where condensation builds up under the tarps and moisture accumulates.

By contrast, in stockpiles where the initial moisture content of in-hull almonds was low—at or below 5.7% total fruit moisture content—there was minimal mold growth and no aflatoxin production.

The studies will continue this year to refine guidelines, but these findings suggest:

• To be on the safe side until more is known, in-hull almonds that have a total moisture content exceeding 6.5-7% should not be stockpiled. As a practical guide, kernels, shells and hulls that "snap" when bent between fingers are certainly safe.
  
  
• If piles are stacked too wet, there will be condensation and mold growth at the outer portions of the piles. Consider opening up the piles in the daytime when relative humidity is lower, and closing them at night when relative humidity is high.
  
  
• For more details on managing stockpiles to reduce aflatoxin potential in almonds, click here to read an article by Bob Curtis, Associate Director, Agricultural Affairs, Almond Board of California.