| Pesticide residues are an important influence on the quality and safety level of edible agricultural products.Based on this,scholars at home and abroad have carried out the identification and screening of relatively high risk pesticide residues in dozens of fruits and vegetables,such as dragon fruit,cucumber and tomato,etc.In contrast,the reports of relatively high risk pesticide residues in watermelon are rare.Thus,in this paper,we integrated high performance liquid chromatography tandem mass spectrometry,gas chromatography tandem mass spectrometry,chronic and acute dietary risk,risk ranking,separation of subcellular fractions and other technical methods to carry out the identification of relatively high risk pesticide residues in watermelon fruits,the dissipation dynamics of relatively high risk pesticide residues in watermelon fruit rind and pulp and their migration characteristics,the distribution pattern of relatively high risk pesticide residues in watermelon fruits,the distribution pattern of relatively high risk pesticide residues in watermelon fruits,the distribution pattern of relatively high risk pesticide residues in watermelon fruits and the distribution pattern of relatively high risk pesticide residues in watermelon fruits.The results of these studies can provide support for the continuous improvement of the level of precise control of pesticide residues in watermelon,and the scientific control of relatively high risk pesticide residues in watermelon fruits.The main research results are as follows:(1)With 422 watermelon samples from 4 provinces as the research object,the quantitative analysis of 60 pesticide residue levels in the samples was carried out by gas chromatography tandem mass and liquid chromatography tandem mass spectrometry,and then the assessment of relatively high risk residual pesticides,identification of residual pesticides and dietary risk assessment using chronic and acute dietary risk,risk ranking and other technical methods.The results showed that: the total number of residual pesticides in the samples was 18;the %ADI and %ARf D values of residual pesticides were much less than100%,and the risk scores of three pesticides,methomyl,pyridaben,and triazophos,were above 20,which were relatively high risk residual pesticides.(2)Triazophos is a banned pesticide and the dietary risk of mevinphos is higher than that of pyridaben.Therefore,the residual dissipation dynamics of mevinphos in two peels,two flesh and subcellular fractions were monitored by liquid chromatography tandem mass spectrometry after mevinphos immersion treatment at a concentration of 0.3525 mg/kg for 8-48 h.The migration characteristics were also elucidated from the subcellular structure perspective.The results showed that the residual dynamics of mevalonate in watermelon showed the same trend of mevalonate residues in whole fruit rind and pericarp,whole fruit flesh and flesh during 8-48 h.The difference was that the residual level of mevalonate in pericarp was higher than that in whole fruit rind,and the residual level of mevalonate in whole fruit flesh showed an increasing trend,which suggested that there was pesticide migration between pericarp and flesh of watermelon fruits after harvesting;the residual level of mevalonate in whole fruit rind during 32-48 h was higher than that in whole fruit flesh.The distribution of mevalonate in the peel was in the cell wall,organelle and membrane,and soluble components within 32-48 h.The subcellular distribution of mevalonate in the flesh of whole fruit at 8-40 h was: organelle and membrane > cell wall,and the residual level of mevalonate in the flesh of fruit at 8-48 h was slowly increasing in the organelle and membrane components,and there was no obvious pattern in the remaining two components.This suggests that the migration of mevalonate from the cell wall,organelles and membranes and soluble fractions of the whole fruit peel to the whole fruit flesh was easier with time.(3)The residue distribution patterns of mevalonate in 10 different parts of watermelon fruit were investigated by liquid chromatography tandem mass spectrometry after fruit soaking at concentrations of0.1900 mg/kg,0.2350 mg/kg and 0.3525 mg/kg,respectively.The results showed that the residual levels of mevinyl salts in the fruit skin and fruit stalk were higher than those in other parts of the fruit after low and medium concentrations;with the increase of the concentrations,the overall trend of the differences in the residual levels of mevinyl salts in different parts of the fruit skin and fruit flesh was gradually reduced.This suggests that the distribution of mevalonate residues may be related to the content of nutrients in different parts of the fruit,and there is a possibility that mevalonate may be redistributed in different parts of the fruit.(4)Ten parts of watermelon fruits treated with mevalonate at a concentration of 0.3525 mg/kg were analyzed by high performance liquid chromatography for the contents of six nutrients: fructose,glucose,total sugar,citric acid,malic acid,and total acid,and then the data on the distribution of the six nutrients and mevalonate residues were integrated to explore the influence of the distribution of relatively high risk pesticide residues in watermelon fruits Factors.The results showed that the contents of citric acid,malic acid and total acid in the rind > flesh,and the contents of fructose,glucose and total sugar in the rind <flesh,and the six nutrients differed between the rind and flesh parts.The high content of total sugar and low content of malic acid and total acid in the stalk part of fruit flesh were the apparent phenomenon that the residual level of mevalonate in this part was higher than that in other parts.This indicates that the high total sugar content and low total acid content are important characteristics for the high level of mevalonate residues in the flesh and stalk parts of the fruit skin,which may be an important quality indicator affecting the distribution of mevalonate residues. |
PDF Full Text Request