Comparison of pesticides levels in grape skin and in the whole grape by a new liquid chromatographic multiresidue methodology

The increasing interest in the study of pesticides in grapes is justified from an enological point of view, since some pesticides can interfere with fermentative microflora used in wine production, as well as, with the consumer’ safety. Considering that washing grapes before consumption is the standard procedure, the study of the effect of washing on the residue concentration is required to assess real consumer exposure. In this work, pesticide mobility in grapes was studied, by comparing their residual concentration in the skin with that of the whole grape. The efficiency of water washing to remove pesticides from grape skins was also evaluated. One variety of grapes from the Northern region of Portugal, Trajadura, sampled at two maturation periods of the 2001 crop, were analysed by a new validated methodology involving liquid chromatography with diode array detection. It was concluded that, although there were no significant differences between some pesticide levels found in the whole grape (skin and pulp) and in the grape skin, pyrimethanil was preferably found in the pulp, while metalaxyl was detected in the skin but not in the whole grape. The removal of pesticides from grapes by washing did not exceed 70% (procymidone). Never the less, it was concluded that consumer intake of the pesticides from grapes studied in this work should be significantly decreased as a result of water washing of the grapes. The concentration levels found for the pesticide residues were below both the Portuguese and the FAO Maximum Residue Levels (MRLs), thus causing no problems in terms of food safety.