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 tomat o products were carried out. The effects of the pesticide on some enzy me 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 identifica tion of the studied pesticide and ensured that profenofos extraction a nd cleanup steps were acceptable. The fresh tomatoes had considerable amounts of profenofos (26.6-8.7 ppm) depending on the time from pestic ide application. Washing tomatoes with tap water resulted in about 15- 30 % reduction of the pesticide residues. More residues (89 %) were re moved as the treated tomatoes were processed into tomato juice. Moreov er, the pesticide residues did persist in tomato puree (1.57 ppm) and tomato paste (1.16 ppm). Transaminases were differently affected by pr ofenofos residues. While glutamic-pyruvic transaminase was inhibited b y the residues, glutamic-oxaloacetic transaminase was stimulated. In a ddition, peroxidase and polyphenol oxidase activities were induced. Th e 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. Cons equently, an increase of the V(max) was observed (7.353 units) for pol yphenol oxidase in the profenofos-treated tomatoes as compared to that (4.629 units) of the untreated tomatoes. The pesticide treatment incr eased the total soluble solids and acidity contents but decreased the glucose, protein, and ascorbic acid contents of tomatoes.