Date of Award
Master of Science
Food Science and Technology
M.R. Johnson, D.L. Coffey
The agricultural applications of pesticides have played an important role in increasing the yield of food products throughout the world. It is unfortunate that residues of pesticides are sometimes found on food products before and after processing. Attempts have been made to reduce the levels of various pesticides in food products, but they have been relatively unsuccessful. This study was designed to determine the effect of epoxy-phenolic enamel on levels of DDT [1,1,1- trichloro-2,2-bia(p-chlorophenyl)ethane] and its metabolites in turnip greens during blanching and thermal processing.
Turnip greens were grown on three plots and were given periodic spray applications of DDT. The greens were harvested, washed, and blanched by steam for three minutes or in boiling water for three or five minutes. A steam-jacketed kettle was used for water blanching and was operated with and without an interior lining composed of epoxy-phenolic enamel coated tin plate. Greens blanched by steam or in water for three minutes were thermally processed subsequently at 121°C for 45 minutes. The greens were thermally processed in plain tin plate cans or epoxy-phenolic enamel lined cans.
Samples of greens were taken at the following times: prior to the first application of DDT, prior to washing, and immediately following each of the process treatments. The pesticides were extracted by macerating the plant tissue with acetonitrile followed by eluting the extract through a column of Florisil to remove other interfering materials. The extract was analyzed quantitatively by gas liquid chromatography to determine levels of DDE [l,l-dichloro-2,2-bis(p-chloropheny1)ethylene], DDD [1,l-dichloro-2,2-bis(p-chlorophenyl)ethane], o,p'-DDT [l-trichloro-2-o-chlorophenyl-2-p-chlorophenylethane], and P,p'-DDI [1,trichloro-2,2-bis(p-chlorophenyl)ethane].
The data indicated that low concentrations of o,p'-DDT and p,p'-DDT were present in the turnip greens prior to the first application of the pesticide material. Residues remaining in or on the greens at the time of harvest were in excess of the established tolerance limits. Blanching methods and blanching times in water did not produce significant different levels of residue. Enamel lining in kettles or cans did not significantly reduce the levels of pesticides during blanching or thermal processing.
From the results of this study, it is evident that epoxy-phenolic enamel does not have an absorptive capacity for DDT or its metabolites, and is not an effective means of reducing residue levels.
Fair, James G., "Effects of epoxy-phenolic enamel on DDT, DDD, and DDE during blanching and thermal processing of turnip greens. " Master's Thesis, University of Tennessee, 1972.