The Degradation Of Some Pesticide Residues In Cucumber, Tomato And Apple During Their Processing

The risk assessment of pesticide residue is based on the raw agriculturalcommodities (RAC), while less to consider the influence of different processing onpesticide residues. This will lead to the result that the dietary exposure risk assessmentof people is not accurate, so it is important for us to study the residue change of thepesticide during the processing. This study chose the cucumber, tomato, apple as themodel crop to study the dynamic variation of the pesticide residue during theirprocessing. This paper focused on the studies as follows:1. The pickled process of cucumber: The degradation of chlorpyrifos and itsmetabolite3,5,6-trichloro-2-pyridinol (TCP) in cucumber during pickled process wasassessed. Results showed that the amount of chlorpyrifos after washing reduced34.0%, while the amount of TCP after washing only reduced2.6%. The processingfactors of chlorpyrifos and TCP were0.66and0.97, respectively. After the primaryand secondary pickling process, the residues of chlorpyrifos obviously rose to thelevel before washing and the total processing factor of the three processing steps is0.97, while the residues of TCP were significantly increased over the level of washingand the total processing factor of the three processing steps is1.63. This indicated thatthe level of chlorpyrifos has no obvious change in cucumber after pickling process,while the residues of its metabolite TCP were obviously increased.2. The home canning of tomato paste: The behaviors of home canning on residuelevels of chlorpyrifos and its metabolite TCP in tomatoes were investigated. Resultsshowed that the amount of chlorpyrifos after washing reduced29.9%, while theamount of TCP after washing remained the same as that in raw tomatoes. Chlorpyrifosand TCP were proved to be mostly retained in tomato skin. The peeling processcaused the loss of63.5%of chlorpyrifos and53.3%of TCP from tomatoes, with theprocessing factor of peeling at0.09and0.43, respectively. The tomato juice and seedswere found free of chlorpyrifos residue, but detected TCP residue. In addition, due tothe heat treatment, some of the chlorpyrifos was lost by volatilization or hydrolysis and some was degraded to TCP during simmering process. Moreover, sterilizationreduced the residues of chlorpyrifos by23.3%and gave rise to the increase of TCP by8.3%. The PF of the overall process for chlorpyrifos and TCP was0.06and0.80respectively, indicating that the whole process can reduce the residue of chlorpyrifosobviously, while only reduce a little of the residue of TCP.3. Apple cider processing: The fate of spirotetramat and its metabolite B-enol inapple samples during apple cider processing was assessed. Results showed that theconcentration of spirotetramat and B-enol residues significantly decreased in applecider after systematic processing. The PFs of apple samples after each step weregenerally less than1except that the PF of B-enol after sterilization was larger than1.The sterilization process reduced the residues of spirotetramat by37.7%and gave riseto the increase of B-enol by33.4%. Spirotetramat and B-enol were proved to bemostly retained in apple peels. The peeling&coring process caused the loss of76.4%of spirotetramat and62.9%of B-enol from apples, with the processing factor ofpeeling&coring at0.14and0.22respectively. While the PF of the overall process forspirotetramat and spirotetramat-enol was0.02and0.07respectively, indicating thatthe whole process can reduce the residue of spirotetramat and spirotetramat-enol inapple cider obviously.Our research results have significant importance for detecting the levels ofpesticide residues and their changes in the products of processed crops and fruits,dietary exposure risk assessment and optimizing the processing technology of theagricultural products.