Residual Behaviors Of Six Pesticides In Shiitake From Cultivation To Postharvest Processing And An Assessement Of Their Dietary Risk To Consumers

Shiitake(Lentinus edodes)is the second most cultivated edible mushroom in the world,accounting for about 25%of the worldwide production of mushrooms.The nutritional properties and health benefits of the "medicinal" mushrooms have been recognized.Shiitakes are susceptible to a variety of diseases and insect infestations due to the high temperature and humidity required for adequate fruiting body growth.Therefore,pesticides are usually used to control disease outbreak and insect infestations during cultivation.The pesticides are sprayed directly on the fruiting body or are premixed with the substrates,which may lead to the accumulation of pesticide residues,potentially harmful to humans,the environment and international trade.Therefore,the six pesticides were divided into two groups:the systemic pesticides(carbendazim,thiabendazole,procymidone);contact pesticides(bifenthrin,?-cyhalothrin,?-cyfluthrin).The dissipation of two groups(six pesticides)in shiitakes from the field to the postharvest processing was investigated and the dietary exposure risk was estimated therafter.The contents and results are as following:1.The dissipation behaviors of two group pesticides in three different substrates(nonsterilized substrate,sterilized substrate without shiitakes strains and sterilized substrates with shiitakes strains)were investigated and the dissipation behaviors of two groups(six pesticides)in shiitakes under open filed conditions via two application treatments(premixing and spraying).Results indicated that the dissipation rate of the systemic pesticides followed a trend:nonsterilized substrate>sterilized substrates with shiitakes strains>sterilized substrate without shiitakes strains;the dissipation rate of the contact pesticides followed a trend:sterilized substrates with shiitakes strains>nonsterilized substrate>sterilized substrates with shiitakes strains.The half-lives of the systemic pesticides(t1/2:8.1?27.2 d)in substrates are less than the contact pesticides(t1/2:27.9?94.6 d).For the premixing treatment,the residues of systemic pesticides is increasing in shiitakes,however the residues of contact pesticides is decreasing in shiitake.The final residues of carbendazim,thiabendazole and procymidone were 0.088?0.154,0.103-0.151 and 0.080?0.142 mg/kg.The final residues of bifenthrin,?-cyhalothrin,?-cyfluthrin were below the limit of quantitation.The final six pesticide residues in shiitakes were below the standards of EU-MRLs,except for procymidone.For the spraying treatment,the half-lives of the systemic pesticides(t1/2:11.7?25.6 h)in shiitakes are less than the contact pesticides(t1/2:44.1-68.2 h).The final residues of the above pesticides were 0.642?0.905,0.130?0.452,0.379?0.472,0.039?0.098,0.022?0.038 and 0.024?0.042 mg/kg,only carbendazim and thiabendazole were below the standard of EU-MRLs.2.The effect comparison of two drying methods(sunlight exposure and hot-air)was investigated on the residue dissipation behaviors of two group pesticides in shiitakes as well as the determination of the corresponding processing factors(PF).The effect of different pH solution on the dried shiitakes was investigated.Results indicated that the final PF for the six pesticides were larger than 1 during two drying processes,except for thiabendazole upon sunlight exposure drying.The PFs of systemic pesticides(0.42?1.71)were less than the PFs of contact pesticides(3.77?4.93)in shiitakes after sunlight exposure drying.The PFs of the systemic pesticides(2.47?4.10)were less than the PFs of the contact pesticides(4.56?5.73)in shiitakes after hot-air drying.The residues of 5-hydroxythiabendazole increased significantly after hot-air drying.Rehydrating with 2%dietary alkali solution at 40 ? for 150 min was the recommended way to eliminate all the six pesticides from the dried shiitakes due to the PF(0.027?0.065)for six pesticides were lowest.3.The change of two group pesticides and metabolites of two pesticides residual concentration was investigated in processed shiitakes during canned shiitakes as well as the determination of the corresponding processing factors.The change of six pesticides residual concentration in shiitakes was investigated under washing,soaking,ultrasonic cleaning and discontionous ozone water cleaning and continuous ozone water cleaning.Results indicated that the canned processing exhibited a significant effect on removal of six pesticides(PF<1).The PFs of the systemic pesticides(0.18?0.27)were less than the PFs of the contact pesticides(0.47?0.59)in shiitakes during the whole canned processing.The residual concentration of 5-hydroxythiabendazole was not influenced by processing of canned shiitakes,but the residual concentration of 2-aminobenzimidazole increased significantly during sterilization,lead to the PF>1.Washing,discontinuous ozone cleaning,continuous ozone cleaning and ultrasonic cleaning can reduce the concentration of six pesticides in shiitakes around 0?42.90%,6.26%?33.02%,8.56%?67.32%and 24.57%?63.81%.4.The household processing impacts the residue behaviors of two group pesticides in shiitakes was investigated as well as the determination of the corresponding processing factors.Results indicated that the half-lives of systemic pesticides(t1/2:37.9-47.3 d)were larger than contact pesticides(t1/2:29.8?32.4 d)druing the storage condition of 4?.The half-lives of systemic pesticides(t1/2:5.1-6.3 d)were less than contact pesticides(t1/2:12.2?16.4 d)druing the storage condition of 20?.The PFs of systemic pesticides(0.26?0.77)were less than contact pesticides(0.75?1.20)during boiling processing under the same treatment time;the PFs of systemic pesticides(0.65?0.79)were larger than contact pesticides(0.21-0.59)during frying processing.Stir-frying and frying increased significantly the residues of 2-aminobenzimidazole and 5-hydroxythiabendazole(P<0.05).The concentration of 2-aminobenzimidazole was 0.054-0.311 mg/kg in reused oil.Washing 10min + boiling 20 min(PF:0.17-0.36)and washing lOmin + flying 60 s(PF:0.19?0.24)are recommended way to eliminate the tested systemic pesticides and contact pesticides in fresh shiitakes.5.The dietary exposure risk of the six pesticides in processed shiitakes was investigated based on field trial data and processing factors.Results indicated that the dietary risk of the the six pesticides in canned shiitakes,rehydrated shiitakes and househole processed shiitakes(hazard index:0.02%?4.08%)were lower than freshed shiitakes(hazard index:0.35%?42.45%).The chronic hazards of the the six pesticides in hot-air dried shiitakes(chronic hazard quotient:0.35%?42.45%)were lower than freshed shiitakes(chronic hazard quotient:0.14%-14.89%).As a sonsequence,the dietary risk for the six pesticides in the dried shiitakes,canned shiitakes,rehydrated shiitakes and househole processed shiitakes for each tested pesticide can be considered acceptable(hazard index:0.02%?2.45%).