Degradation of organophosphorus pesticides in cereal grains during milling and cooking in India.

Samples of paddy (rough rice), wheat, and sorghum were treated
with different concentrations of malathion, Gardona. and
5umithion lor protection against insect infestation during storage.
Subsequently, samples were milled. cooked. and analyzed by 9a$liquid
chromatography to determine residues remaining in the final
products. Malathion and Gardona treatments ranged from 1Oto 80
p.p.m.• Sumithion treatments, from 2 to 16p.p.m. During machine
milling, reSidues in wheat and sorghum were decreased from 30to
70%. Because residues were concentrated in the hull and bran of
the paddy, relatively little remained on polished rice after milling.
Even with treatments of 80 p.p,m. residues on polished rice were
never more than 4p.p.m. Milled products from each grain were
cooked using traditional Indian methods. Preparations involving
!roiling or steaming (wet cooking} resulted in complete degradation
(loss) of residues of all three protectants so far as detectable with
methods sensitive to less than 0,1 p_p.m. Dry cooking methods,
used in preparing chapatties from wheat and sorghum, resulted in
average losses of 43 to 75% of residues.