Residual Dynamics And Depletion Of Two Pesticides In Lentinus Edodes During Growing And Processing

Lentinus edodes is an important kind of epiphyte which can be used as medicine and food.It has been cultivated in China for long time. Due to using pesticides to prevent and cure pests and diseases of Lentinus edodes,as well as taking the crop straw, wood with residual pesticide as substrate,which can make Lentinus edodes absorbe and enrich some pesticides and be harmful to health of customers.Therefore the problem of pesticide residue for Lentinus edodes has been given attention.Fipronil and Avermectin are taken as two pesticides studied.the trial researches on residual degradation dynamic law of pesticides studied for Lentinus edodes and its substrate and effect of processing factors on the two residual pesticides for Lentinus edodes. providing the guide for quality safety of Lentinus edodes production is the purpose of the trial.The main results of the research are as follows:1. Residual analytical methods for fipronil and Avermectin for Lentinus edodes and its substrate are established. Fipronil is extracted by ethyl acetate with a mechanical oscillation, and purified by glass-column chromatography with florisil, detected by GC with ECD. The results showed that with the level of fortification ranging from 0.01mg/kg to 1mg/kg, the fipronil recoveries of fortification for Lentinus edodes and its substrate are 83.93%~90.53% and 78.97%~108.14%,respectively.RSD is less than 13% and LOQ is 4μg/kg.Avermectin is extracted by the mechanical oscillation using acetonitrile as extraction solvent, purified by Alumina-N SPE, detected by HPLC-FD. The results showed that with the concentration of fortification ranging from 0.01mg/kg to 0.5mg/kg, the Avermectin recoveries of fortification for Lentinus edodes and its substrate are 75.55%~90.98% and 79.07%~106.68%,respectively.RSD is less than 12% and LOQ is 5μg/kg.Both fipronil and Avermectin residue analysis methods can meet the requirement of pesticide residue analysis.2. The results of the residue field trials in Beijing and Hefei indicates that the degradation half-life of fipronil is 1.54d~1.90d for Lentinus edodes, 2.66d~3.00d for substratel; Avermectin is 1.78d~2.11d ,2.88d~3.27d,respectively.Thus, both in Beijing and Hefei, the degradation dynamics tendency of the two pesticides studies are basically the same, and so is the degradation half-life.The final residue trials of the two pesticides indicate that if with taking the maximum recommended dose of the two pesticides as using dose,the quality of Lentinus edodes sprayed is safe to eat after 5 days from spraying pesticide beginning, and the final residuals of fipronil and Avermectin are 0.019mg/kg~0.033mg/kg, 0.019mg/kg~0.028mg/kg, respectively.3. Within the residues studies,the results of effect of three drying patterns on fipronil and Avermectin residue for Lentinus edodes indicate that: outdoor sun-drying pattern influences pesticide residues most, and the decreasing rate of residual pesticide is 49.77%~56.60%,34.43%~55.34%; indoor drying naturally ranks the second, and the decreasing rate of residual pesticide is 34.10%~42.88% ,24.59%~37.55%; the freezing-drying affects lest, and the decreasing rate of residual pesticide is 13.30%~20.75%,12.30%~22.22%.Within the residues studies,comparing washing by clean water with immersing by clean water, washing can decrease pesticide residues better .It can decreaing 17.65%~79.44% residual fipronil,7.14%~52.96% residual Avermenctin,but immersing can only decrease9.17%~30.19%,11.48%~29.64%, respectively.