Recommended Storage Moisture Content for Dry Edible Beans
August 29, 2007
There are limited studies on the allowable storage time of edible beans, but the results from corn can be used to estimate the storage moisture content and storage time for edible beans. The equilibrium moisture content of edible beans is similar to corn, so expected recommended storage moisture contents should be similar.
The maximum allowable storage time for 18% moisture corn at 50 degrees is 3.4 months. Cooling the 18% moisture corn to 40 degrees extends the maximum storage period to about 6.1 months. Therefore, edible beans can be stored at 18% moisture content during the fall and winter if they are cooled with an aeration system so they are no warmer than 50°F in October and 30 degrees in November. Lower moisture contents should be used if longer storage periods are desired or the beans cannot be cooled to the specified temperatures. Corn at 16% moisture is expected to store for about nine months at 60°F, which is the basis of the 15.5% moisture content recommendation during fall through spring.
A moisture content of 16% should normally be considered the maximum recommended short term storage moisture content for edible beans.
For long-term storage the moisture content must be low enough to permit storage without deterioration at typical summer temperatures. For example, the recommended long-term storage moisture content for wheat is normally at about 13%. This keeps the relative humidity in the wheat below 65% at 70 degrees, which limits mold growth. The recommendation for edible beans is also about 13% based on the same considerations.
If the beans can be kept cooler, the acceptable moisture content can be increased. If the beans can be kept at 60°F or cooler, the moisture content can be 14% for long term storage.
It is important to follow good storage management practices such as measuring the temperature and moisture content of the beans at least monthly. Whenever there is more than a 10 degree differential between the average outdoor temperature and the bean temperature during the fall, the beans should be cooled with aeration. This should continue until beans at 16% moisture are cooled at least to 40°F and 18% moisture beans are cooled to about 30°F. Cooling below 30 degrees is not necessary and may increase the potential for handling damage.
From the NDSU Dry Bean Production Guide, www.ag.ndsu.edu/pubs/plantsci/rowcrops/a1133-1.htm.