Changes in pesticide residues in field-treated fresh grapes during raisin production by different methods of drying

Drying is one of the best food preservation methods, especially for grapes. This study aimed to determine the fate of pesticides after grapes are being subjected to different drying methods, namely, sun-, oven-, shade-, and alkaline-drying, which are employed in raisin production. Pesticide residues were determined by gas chromatography–tandem mass spectrometry (GC–MS/MS). Washing before drying decreased the diazinon, ethion, phosalone, penconazole, and hexaconazole levels in the grape samples by 52.04%, 6.75%, 9.99%, 56.54%, and 20.97%, respectively. In the raisins, the concentration of all the pesticide residues increased based on wet weight, and this result was due to dehydration; by contrast, the concentrations of the pesticides decreased based on dry weight. The sun-drying method demonstrated the greatest efficiency in residue removal wherein it decreased the diazinon, ethion, phosalone, penconazole, and hexaconazole levels by 76.65%, 68.40%, 69.55%, 72.74%, and 82.19% (dry weight), respectively. On the contrary, the shade-drying method demonstrated the least efficiency in reducing the residue levels (19.57%–42.55%). The evaluation of the processing results showed pesticide residue level in the raisins prepared using the investigated drying methods was higher than the maximum residual limits (MRL). This finding indicates that it is necessary to consider the pre-harvest interval in pesticide application in grape.

干燥是极具应用价值的食品保鲜手段之一，在葡萄的加工保藏领域尤为常用。本研究旨在探究葡萄经葡萄干生产中常用的四种干燥方式——日光干燥、烘箱干燥、阴凉干燥与碱性干燥处理后，其中农药的归趋变化。本研究采用气相色谱-串联质谱（gas chromatography–tandem mass spectrometry, GC–MS/MS）测定样品中的农药残留量。干燥前水洗可使葡萄样品中的二嗪磷（diazinon）、乙硫磷（ethion）、伏杀硫磷（phosalone）、戊环唑（penconazole）以及己唑醇（hexaconazole）的残留量分别降低52.04%、6.75%、9.99%、56.54%和20.97%。以湿重为计重基准时，葡萄干中所有农药残留的浓度均因脱水作用而升高；与之相反，以干重为计重基准时，农药残留浓度则呈下降趋势。日光干燥法展现出最高的农药残留去除效率，以干重计，其可使二嗪磷、乙硫磷、伏杀硫磷、戊环唑以及己唑醇的残留量分别降低76.65%、68.40%、69.55%、72.74%和82.19%。与之相反，阴凉干燥法的残留去除效率最低，仅能实现19.57%~42.55%的残留降低率。加工结果评估显示，经本次研究涉及的干燥方式制备的葡萄干中，农药残留量均超过最大残留限量（maximum residual limits, MRL）。该结果提示，在葡萄的农药施用过程中，需充分考虑采前安全间隔期的合理设置。