GC-ECD AND GC-MS ANALYSES OF PROFENOFOS RESIDUES AND ITS BIOCHEMICAL EFFECTS IN TOMATOES AND TOMATO PRODUCTS

GC-ECD and GC-MS analyses of profenofos residues in tomatoes and tomato products were carried out. The effects of the pesticide on some enzyme systems (transaminases and oxidoreductases) and quality attributes of tomato fruits were also studied. The results showed that the GC-ECD analysis allowed an accurate determination of profenofos residues. GC-MS analysis was less susceptible to interfering compounds than the GC-ECD analysis. In addition, the GC-MS technique allowed the identification of the studied pesticide and ensured that profenofos extraction and cleanup steps were acceptable. The fresh tomatoes had considerable amounts of profenofos (26.6-8.7 ppm) depending on the time from pesticide application. Washing tomatoes with tap water resulted in about 15-30 % reduction of the pesticide residues. More residues (89 %) were removed as the treated tomatoes were processed into tomato juice. Moreover, the pesticide residues did persist in tomato puree (1.57 ppm) and tomato paste (1.16 ppm). Transaminases were differently affected by profenofos residues. While glutamic-pyruvic transaminase was inhibited by the residues, glutamic-oxaloacetic transaminase was stimulated. In addition, peroxidase and polyphenol oxidase activities were induced. The apparent K(m) of the profenofos-treated tomatoes was lower (1.410 X 10(-4) M) than that (3.891 x 10(-4) M) of the untreated tomatoes. Consequently, an increase of the V(max) was observed (7.353 units) for polyphenol oxidase in the profenofos-treated tomatoes as compared to that (4.629 units) of the untreated tomatoes. The pesticide treatment increased the total soluble solids and acidity contents but decreased the glucose, protein, and ascorbic acid contents of tomatoes.