Chemical Morphology And Subcellular Structure Resolution Of Arsenic And Cadmium In Different Parts Of Melon Fruit And Assessment Of Their In Vitro Digestibility

Melon is an advantageous agricultural product in China and the region.The team’s preliminary research found that there is a potential risk of arsenic and cadmium contamination in the soil of some melon fields(the risk is still at a manageable level),and the enrichment levels of arsenic and cadmium in different parts of the melon fruit vary.Therefore,in this paper,we have carried out the study and analysis of the chemical morphology,subcellular structure and distribution of arsenic and cadmium in different parts of melon fruits by combining chemical morphology step-by-step extraction,subcellular fraction separation,in vitro digestion,inductively coupled plasma mass spectrometry and other technical methods,and conducted six chemical morphologies and three subcellular structures of arsenic and cadmium in different parts of melon fruits.The study and evaluation of the in vitro digestion and release rates of arsenic and cadmium in different parts of melon fruits were carried out,with a view to supporting the study and construction of techniques for the regulation of the distribution of major contaminating heavy metals in fruits,the processing and utilization of different parts of fruits and the safety evaluation.(1)The six chemical forms of heavy metals arsenic and cadmium were extracted from ten parts of melon fruits by stepwise extraction method,and the contents of the different chemical forms were analysed by inductively coupled plasma mass spectrometry.The results showed that among the six chemical forms of arsenic in different parts of the melon rind,the sodium chloride extracted state and the residual state accounted for a relatively high proportion,while the ethanol extracted state,sodium chloride extracted state and residual state accounted for a relatively high proportion in the fruit flesh.The distribution of the same chemical form of arsenic in different parts of the fruit varied,but its distribution was not potentially related to the distribution of total arsenic.Among the six chemical forms in different parts of the melon rind,the ethanol-extracted state and the deionised water-extracted state had a relatively high proportion of cadmium,while the ethanol-extracted state had a relatively high proportion of cadmium in the fruit flesh.It can be concluded that the residual state and the sodium chloride extracted state have a certain influence on the distribution of cadmium in melon rind and flesh,respectively,and are important forms for regulating the distribution of cadmium in melon fruits.(2)Ten parts of melon fruits were used for the study.The three subcellular fractions were separated by differential centrifugation and quantitatively analysed by inductively coupled plasma mass spectrometry.The results showed that among the three fractions of melon rind and flesh,the arsenic content of the cell wall fraction was significantly higher than that of the other two fractions;in contrast,the cadmium content of the soluble fraction was higher than that of the other two fractions.In terms of the distribution of different parts of the rind and flesh,the cell wall fraction was consistent with the distribution of arsenic enrichment in the rind and flesh of melon,while the soluble fraction was close to the distribution of arsenic in the flesh of melon;the cell wall fraction was opposite to the distribution of cadmium in the rind of melon,while the cell wall fraction and organelle fraction were close to the distribution of cadmium in the flesh of melon.This indicates that the cell wall fraction is an important subcellular structure that affects the distribution of arsenic and cadmium in the melon rind;in addition,the soluble fraction and the organelle fraction also have some influence on the distribution of arsenic and cadmium in the flesh.(3)Based on the separation and extraction of six chemical forms of arsenic and cadmium from 10 different parts of melon fruits,the in vitro digestion and release rates of six chemical forms of arsenic and cadmium from 10 parts of melon fruits were investigated and evaluated by inductively coupled plasma mass spectrometry using the RIVM method.The results showed that the digestion and release rates of different chemical forms of arsenic from the flesh and rind parts were relatively high for the ethanol extracted state and the sodium chloride extracted state,and among the different parts,the digestion and release rates of heavy metal arsenic from the ethanol extracted state and the sodium chloride extracted state were higher for parts H,F and C,respectively.The digestion and release rates of cadmium from the flesh were higher in the hydrochloric acid extracted state and the residue state,and the release rates of cadmium from the different parts were relatively higher in parts H and J.The hydrochloric acid extracted state and the deionized water extracted state were the forms with relatively higher digestion and release rates of cadmium from the peel,and the release rates of cadmium from the different parts were relatively higher in parts B and E.In chapter2 of this paper,it can be seen that: arsenic in the sodium chloride extracted state in part F,arsenic in the ethanol extracted state and sodium chloride extracted state in part C,cadmium in the hydrochloric acid extracted state in part H and cadmium in the hydrochloric acid extracted state in part B have the characteristics of a large proportion,high total content and strong digestive release rate,so in the process of developing new products for melons,it is advisable to focus on the above-mentioned risky parts in combination with the types of heavy metals.(4)Based on the separation of subcellular fractions from different parts of melon fruits,the in vitro digestion of three subcellular structures of arsenic and cadmium in 10 parts of melon fruits was studied and evaluated by inductively coupled plasma mass spectrometry using the RIVM method to simulate in vitro digestion.The results showed that the digestion and release rates of arsenic from the soluble fractions of the three subcellular fractions of the flesh and rind were the highest,and the digestion and release rates of cadmium from the soluble fractions of the four parts F,H,C and B were higher;the digestion and release rates of cadmium from the organelle fractions of the three subcellular fractions of the flesh and rind were higher,and the digestion and release rates of cadmium from the organelle fractions of the three parts G,E and A were relatively higher.Combined with Chapter 3 of this paper,it can be seen that: the soluble fractions of the H part of the fruit pulp and the C part of the fruit peel,and the organelle fractions of the H part of the fruit pulp and the E part of the fruit peel have the characteristics of high arsenic and cadmium content,high proportion and strong digestive release rate,so in the process of safety evaluation,it is appropriate to focus on the risk of contamination of the H part of the diet;in the process of fruit peel processing and utilization,it is appropriate to focus on the C and E parts of the heavy metal arsenic and cadmium.