Measuring Peanuts' MoistureWhile Still in the
October 31, 2007
Making sure that U.S. peanuts are
top-quality requires drying them enough to prevent growth of fungi that can
seriously decrease their market value. Now, Agricultural Research Service (ARS) scientists have developed a way to
determine moisture levels without destroying the peanuts' shells, or pods, as
is currently done. ARS is the U.S. Department of
Agriculture's chief scientific research agency.
Market value is directly tied to peanut quality, and one of the most
important quality factors is moisture content. Peanuts must be dried, or cured,
to ensure the moisture content does not exceed 10.5 percent, to ensure quality
is preserved and to prevent growth of microbes naturally present in farm
fields. One of these, the fungus, Aspergillus flavus, can produce a
potentially dangerous mycotoxin called aflatoxin.
O. Nelson have pursued an alternative to opening pods for testing. Instead,
they place intact peanut pods between two plates of an impedance analyzer and
use radio frequency to determine the pods' moisture content.
Kandala works in the
National Peanut Research Laboratory in Dawson, Ga. Nelson works in the
and Safety Assessment Research Unit of the
Richard B. Russell Research Center in Athens, Ga.
U.S. producers have systems in place to reduce moisture content, but the
trick is to make sure optimal levels are reached throughout an entire batch of
In the Southeast, freshly dug peanutswhich contain up to 40 percent
moistureare allowed to dry on the vine until they reach an average
moisture value of about 20 percent, when they are harvested. Soon after,
they're mechanically dried in special trailers until they reach less than 10.5
percent to meet grading standards and allow for safe storage, given adequate
ventilation. During drying, processors must measure the peanuts' moisture
contents at regular intervals to prevent drying the peanuts too much, which
increases costs and lowers peanut quality.
According to Kandala, the impedance analyzer is better than current methods
at measuring pockets of moisture in the entire batch of peanuts.