Behavior of parathion in tomatoes processed into juice and Ketchup

Abstract

Fresh tomatoes were cut, fortified with 25 ppm (μg/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.

Key words:

• Tomatoes
• tomato juice
• ketchup
• parathion
• pesticide residues