Toxic Weed Seed Contaminants in Soybean Processing

Soybeans are subject to potential contamination from toxic weed seeds during harvest, transportation and storage. The more common foreign seeds include those from jimsonweed, cocklebur, nightshade, cowcockle, corncockle, morning glory, castor, pokeweed, and crotalaria. This review addresses itself to the chemistry and toxic principles of these contaminants. Since jimsonweed seeds are probably the most toxic and most prevalent contaminant of soybeans, they are discussed in greatest detail. A gas liquid chromatographic method for the determination of tropane alkaloids in jimsonweed seeds is described together with the results from analyses of 11 samples found in grain shipments. Results of a nationwide survey of jimsonweed seeds in soybean samples are also included. The fate of jimsonweed seed alkaloids during solvent extraction of contaminated soybeans and alkali refining of crude oil was investigated. Extraction of a 50:50 mixture of soybeans and jimsonweed seeds with petroleum ether yielded meal and crude oil fractions; chemical analysis showed that virtually all the alkaloids remained in the meal. Alkali refining effectively removed atropine added to crude soybean oil.