The effects of milling, washing, and cooking on etofenprox, flubendiamide, and tebufenozide levels in brown and polished rice were investigated by HPLC using a UV detector. The reduction rates of etofenprox, flubendiamide, and tebufenozide after milling were 68.74–93.16%, 64.49–90.25%, and 69.74–92.58%, respectively, 11.64–41.44%, 31.36–65.37%, and 31.61–73.79%, respectively, after washing brown rice, and 30.85–82.08%, 52.13–83.05%, and 43.04–83.89%, respectively, after washing polished rice. The residue levels of the three pesticides in brown rice decreased after electric and pressure cooking by 56.49 and 54.41%, 75.80 and 73.42%, and 70.01 and 71.27%, respectively, and the corresponding levels in polished rice decreased after electric and pressure cooking by 85.58 and 85.82%, 86.70 and 87.06%, and 89.89 and 89.68%, respectively. In conclusion, various processing methods decrease the residual levels of etofenprox, flubendiamide, and tebufenozide in rice.

Pesticides are used to protect crops from pests and diseases. However, as many pesticides are toxic to humans, it is necessary to assess methods that can remove pesticide residues from agricultural products before human consumption. Spinach is consumed immediately after a relatively simple washing and heating process in the Republic of Korea. Cyantraniliprole is used as a systemic insecticide during spinach cultivation, which means it might remain in the crop after processing. Consequently, it is important to assess whether residues can be reduced to levels that are harmless to the human body after processing. This study investigated lowering the residual cyantraniliprole levels in spinach after washing and blanching. The amount of cyantraniliprole residue in the spinach samples sprayed with cyantraniliprole during cultivation was analyzed using ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC–MS/MS). The time of each washing and blanching method was set at 1, 3, and 5 min. The residual levels of cyantraniliprole decreased by 15.1–54.6% and 60.1–93.5% based on the washing and blanching methods employed. The most effective washing method to lower residual cyantraniliprole levels was steeping with a neutral detergent, resulting in cyantraniliprole reduction by 42.9–54.6%. When spinach was blanched after steeping washing with a neutral detergent, the largest removal rates of 77.9 and 91.2% were observed after 1 and 3 min of blanching, respectively. Blanching for 5 min after steeping and running washing exhibited the highest reduction rate of 93.5%. Therefore, a considerable amount of cyantraniliprole residue in spinach could be removed by washing or blanching. Based on the results of this study, blanching after steeping washing can be implemented as an effective method of lowering pesticide concentrations in spinach and other crops, thereby reducing their potential toxicity to humans upon consumption.

This study used gas chromatography combined with the microelectron capture detection method to determine the most effective washing and cooking methods for removing isoprothiolane from rice. The initial isoprothiolane concentrations in brown and polished rice, before washing, were 17.03 mg/kg and 1.67 mg/kg, respectively. Residual concentrations declined with more washing cycles (19.3-59.3% for brown rice; 43.1-66.5% for polished rice); and by increasing the temperature of the washing water from 5°C to 40°C (56.6-63.1% for brown rice; 67.1-74.9% for polished rice). Hand-washing samples using gentle stirring or harsh rubbing reduced pesticide concentrations by 63.1-71.6% for brown rice, versus 75.4-87.4% for polished rice. Reduction in isoprothiolane concentrations varied based on the rice cooker type and whether the rice was pre-soaked. Immediate cooking using an electric- or pressure-cooker showed 78.5% and 78.4% reduction in brown rice, compared with 94.0% and 94.0% for polished rice, respectively. Pre-cooking immersion for 30 min showed similar reductions of 83.4% and 83.4% in brown rice, versus 95.8% and 95.8% in polished rice. The results of this study suggest that the most effective method for removing residual isoprothiolane from both brown rice and polished rice was to wash six times (with vigorous rubbing during the 2nd and 3rd washing) in 7-fold water at 40°C, followed by immersion for 30 min before cooking. Regardless of the type of rice cooker, heating is sufficient to remove an average of 83.4% and 95.8% of isoprothiolane from brown rice and polished rice, respectively.

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