Effects of epoxy-phenolic can linings on DDT in thermally processed turnip greens

Insecticides are used on crops as a matter of course and are considered by most agricultural workers as essential for the provision of the nation's food at acceptable cost and quality. However, there is also a great deal of concern and research concerning the deleterious effects and the avoidance or removal of insecticide residues in food. This study was undertaken to determine whether DDT is absorbed by epoxy phenolic can lining during thermal processing, and whether residues in plain cans were affected differently from residues in cans lined with enamel. Turnip greens were fortified with technical DDT and thermally processed. The insecticide was extracted from plant constituents with acetonitrile and then eluted through a Florosil column to remove other interfering materials. The extraction elution product was then quantitatively analyzed to determine the presence of DDT or its metabolites DDD and DDE. The enamel was removed from the cans with an electrolytic solution and electric current and then treated the same as the plant material had been to extract insecticide residues. Under the experimental conditions reported in this study, several results were indicated. The can enamel absorbed p,p'DDT and apparently catalyzed the rearrangement of some of it to the o,p isomer after absorption. The can enamel did not significantly absorb DDD or DDE during thermal processing. Residues of o,p'DDT in enamel of cans which had been processed at 121° C were significantly higher than in the enamel of cans processed at 116° C. Cook times that achieve commercial sterilization values near Fo7 (normal process) are apparently optimum for the absorption formation of o,p'DDT. Generally, it seems plausible that epoxy phenolic plastics similar to the can linings observed in this experiment might be useful in adventitious removal of chlorinated pesticide residues. However, the reduction of residue in the food that it achieves, though significant, would probably not bring the level down to FDA tolerance if the canned product contained above tolerance levels to begin with. Therefore, epoxy phenolics in forms other than can lining should be studied as a means of reducing residues in food products. For example, partial cooking, prior to canning, in vats or heat exchangers lined with corrugated epoxy phenolic resins might be more absorbent since a larger surface exposure of resin to food would result.