Masters Theses

Date of Award


Degree Type


Degree Name

Master of Science


Food Science and Technology

Major Professor

Melvin R. Johnston

Committee Members

Jimmie L. Collins, Ivan E. McCarthy, Robert R. Shrode


With the increased use of insecticides, much concern has arisen concerning the safety of treated food crops due to the possible retention of the insecticide in the processed product. Insecticidal residues, when present in food-plants, must be removed or decreased in concentration to levels established by the Food and Drug Administration before the food may be consumed.

This study was undertaken to determine whether insecticides are absorbed and stored by the plant; the effect of various methods of weathering, washing, and blanching on decreasing or removing an insecticide; and the effect of thermal processing on an insecticide should it not be removed by the above methods.

Turnips were grown on four plots: Control (no insecticide added); DDT-treated; heptachlor-treated; and DDT + heptachlor-treated. Each of the DDT-treated plots was sprayed with a foliar application of technical grade DDT and the heptachlor-treated plots had been treated with granular heptachlor in the previous planting. In Experiment One, samples of both the turnip greens and turnip roots were taken at final spraying, at harvest, after washing, and after blanching. In Experiment Two, turnip greens were fortified with technical DDT and thermally processed. Plant constituents were removed from any insecticide present by the extraction with acetonitrile followed by elution through a Floricil column to further remove interfering materials. The extraction product was then quantitatively IV analyzed to determine which insecticides were present (heptachlor, hepta- chlorepoxide, DDE, IDE, and DDT). The results were analyzed statistically.

Under the conditions of the study, several conclusions were indicated. In Experiment One, washing and blanching of turnip greens effectively reduced residues of IDE and DDT, but had no significant effect on DDE, heptachlor, and heptachlor epoxide. None of the various processing treatments had a significant effect on root residues. In Experiment Two, thermal processing effected a significant rise in IDE, but had no effect on DDE or DDT. The heat process did not completely dechlorinate DDT to its metabolites, but did cause "feathering" of the can enamel in the DDT-fortified samples.

In general, the results of this study indicate that the processing treatments examined do not reduce the levels of insecticide residues in turnip greens sufficiently to meet Food and Drug Administration specifications for safe human consumption. In cases of high concentration it appears that some dilution procedure or multiple processing must be resorted to in order to meet Food and Drug Administration requirements.

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