Residue Of Imidacloprid In Strawberries And Its Effect On Quality

Strawberry(Fragaria×ananassa)is one of the most important cultivated and consumed cucurbit fruit widely in the world,due to its unique flavor,rich nutritional composition and high economic benefits.Greenhouse cultivation has been the major cultivation method for strawberry in China in recent years.It is easy to cause diseases and insect pests under high temperature,high humidity and continuous cropping conditions of cultivation strawberry.Pesticide residue and its health risk have been focused on in strawberry as well as occurrence and human diet exposure to pesticide residues in strawberries has been reported in recent years.However,the majority studies only focused on the general residue level of pesticides in strawberry from parts of markets which are lack of representativeness.Variety,region and weather conditions as well as sampling time considerably affect the residue of pesticides in strawberries.Therefore,in this study,pesticide residues in different varieties and different harvest time of strawberry have been investigated,and the high-risk pesticides in strawberry have been screened.On this basis,the field residue experiment of Imidacloprid with high detection rate was carried out to study the residue of Imidacloprid in strawberry,and the dietary risk assessment was carried out;the effects of different concentrations of Imidacloprid on Strawberry nutritional quality were studied,so as to put forward the safe and reasonable dosage of Imidacloprid combined with quality maintenance and improvement,and improve the quality and efficiency of strawberry industry.The main contents and findings of this study are as follows:(1)A total of 124 pesticides residue levels of 110 strawberry samples of Beijing were analyzed,dietary risk of imidacloprid in Benihoppe strawberry variety were assessed.The result showed that:Among the three cultivars,Benihoppe cultivar contained the highest number pesticides(45)in Beijing at the whole monitored period.A monthly variation and higher number of pesticides for February(45)compared to the rest four months were found.Imidacloprid was the only registered pesticide that has been detected in strawberry for three consecutive years with a realtively high detection frequency,and the detection rate was 13.5%in 2020.The risk of chronic and acute dietary intake of pesticides in the present study from intake strawberries was less than 100%and with the acceptable risk range,and Chronic dietary risk assessment values of detected pesticides were much less than acute dietary risk assessment values.(2)Residue values of different concentration imidacloprid in Benihoppe and Royal Sovereign cultivar strawberry were studied.The results showed that:imidacloprid residues in the three treatment groups were similar,and the half-life period was 5.98-7.00 d.Concentrations of imidacloprid in the ripe strawberry were low.The final residue test showed that at the recommended dose(20-25 g/mu),after the recommended safe interval(5 days),the concentration of imidacloprid was lower than the MRL(0.5mg/kg)of imidacloprid regulated in China.(3)Objective to evaluate the effects of different concentration imidacloprid on the main quality components of Benihoppe cultivar Benihoppe cultivar strawberry were analyzed.The results showed that:Compared with the control group,the contents of malic acid and vitamin C in Benihoppe cultivar strawberry decreased after treated different concentrations of imidacloprid.Especially,at the dose of 25g/mu,the content of malic acid of Benihoppe strawberry,the content of malic acid and vitamin C of Royal Sovereign cultivar decreased significantly(p<0.05),at the dose of 20 g/mu,similar pattern of vitamin C of Benihoppe strawberry after 2 days of imidacloprid applied.(4)An improved method for matrix-assisted laser desorption ionization mass spectrometry imaging(MALDI-MSI)was developed to analyze vitamin C in strawberry tissues.The results showed that spray-coating 1 m L methanol after automated sublimation 300 mg 9AA methods were used with about25 and 5 times higher sensitivity than spray-coating and automated sublimation methods,respectively.Using negative ion mode monitored the MSI of vitamin C[M-H]~-(175.024)under laser diameter was25?m and laser intensity was 75(arbitrary unit of i MScope).The relative standard deviation of the method was less than 10%,and the lowest detection concentration was 0.01 mg/kg.The robust method was successfully applied for the investigation of visualization analysis of spatial distribution of vitamin C in strawberry,the vitamin C was evenly distributed in the cortex tissue without individual varies.And the content change trend was basically consistent with the Chinese national standard method.