Pesticide residues in raisin processing

The fate of the residues of benalaxyl, dimethoate, iprodione, metalaxyl, phosalone, procymidone, and vinclozolin in sunlight and oven raisin processing was studied. The drying process caused a fruit concentration factor of 4, while the decreases in residue with the two drying processes were different for the different pesticides. In sunlight-drying the residue level in the raisins was identical to that in the fresh fruits for benalaxyl, metalaxyl, and phosalone, whereas it was higher for iprodione (1.6) and lower for vinclozolin and dimethoate (one-third and one-fifth, respectively). The oven-drying process was preceded by washing, which caused residue decreases for iprodione and procymidone of 57 and 41%, respectively, whereas no decrease was observed in all of the other pesticides. During oven-drying pesticide residues in raisins with respect to fresh fruits showed an increase of 2.7 for phosalone, the same values for benalaxyl, metalaxyl, and procymidone, and lower values for vinclozolin and dimethoate. Sunlight-drying was more effective for phosalone and vinclozolin, whereas oven-drying was more effective for iprodione and procymidone, which was due to the washing effect rather than to dehydration. The experiments carried out with a model system showed that the decrease in dimethoate is attributable to heat, whereas in benalaxyl, procymidone, and phosalone it is due to codistillation and in iprodione and metalaxyl to the combined action of heat and codistillation.