Behavior of parathion in tomatoes processed into juice and ketchup

Fresh tomatoes were cut, fortified with 25 ppm (micrograms/g) of parathion (0,0-diethyl 0-4-nitrophenylphosphorothioate) and processed into either juice or ketchup. Tomato juice was canned, while ketchup was placed in bottles. All samples were stored at room temperature for analysis at two-monthly intervals. Parathion residues were measured quantitatively by GLC, while the two metabolites, aminoparathion (0,0-diethyl 0-4-aminophenylphosphorothioate) and 4-nitrophenol, were determined colorimetrically. The presence of the three compounds was confirmed qualitatively by TLC. Blanching of tomatoes resulted in about 50% reduction of parathion level. Pulping of fruits caused a further decrease in parathion residues in juice as a result of its sorption and concentration in the semi-solid pulp. About 85% of parathion added to tomatoes was lost during the processing steps. Storage of juice resulted in a gradual decrease in parathion levels, whereby only 1.7% of the original amount was detected after six months of storage. The compound was stable in ketchup for the first four months of storage but decreased thereafter to almost 7% of the original quantity added to fruits. Aminoparathion and 4-nitrophenol were detected in low levels.