Distribution Of Lead And Cadmium In Chenopodium Quinoa Willd. And The Changes In Processing

Chenopodium quinoa Willd.is a grain-like crop rich in protein,polyphenols,flavonoids and polysaccharides.It not only has antioxidant and anti-inflammatory effects,but also helps lower blood sugar and lose weight.Quinoa rice is mainly used as raw materials to develop quinoa-related products,while quinoa seedlings and quinoa leaves are used as raw materials to develop quinoa green tea and other commercial products.At present,the research on quinoa mainly focuses on its nutrient composition,active ingredient and the technology used in the processing of quinoa-related products,whereas the distribution of heavy metals and the changes that happen in the processing of quinoa are rarely reported,which is not conducive to the safety evaluation of quinoa and the development of quinoa-related products.To solve the problems mentioned above,this study measured the contents of lead and cadmium in quinoa roots,stems,leaves,fruits and different strains of quinoa,to clarify the distribution of lead and cadmium in quinoa;The effects of lead and cadmium on the nutritional quality and safety of quinoa were studied by artificially adding lead and cadmium.Through studying the changes of lead and cadmium in different processing processes of quinoa,and determining the contents of lead and cadmium in quinoa products on the market,the safety of quinoa and its products was finally discussed.The main research results were as follows:(1)Lead mainly concentrated in quinoa roots(0.17 mg/kg~1.06 mg/kg),cadmium mainly concentrated in quinoa leaves(0.22 mg/kg~0.76 mg/kg).The levels of lead and cadmium in fruits were the lowest,0.10 mg/kg~0.29 mg/kg,0.08 mg/kg~0.21 mg/kg,respectively.During the bud stage,filling stage and mature stage,18QS-21 was a safer strain with lower lead and cadmium contents,0.02 mg/kg~0.18 mg/kg and 0.13 mg/kg~0.32mg/kg,respectively.(2)Under lead stress(250 mg/kg~3000 mg/kg),the total lead content of quinoa plants increased as lead concentrations in soil increased(7.09 mg/kg~63.55 mg/kg).The content of lead in the roots was significantly higher than that in the parts above the ground(P<0.05),which was 5.66 mg/kg~60.05 mg/kg,and the differences of lead content in stems,leaves and fruits were small.Lead stress didn't affect the uptake of cadmium by quinoa,and the whole cadmium content was 1.10 mg/kg.Under cadmium stress(20 mg/kg~200 mg/kg),the cadmium content of quinoa increased as the cadmium concentrations in soil increased(12.56mg/kg~105.85 mg/kg).The content of cadmium in the roots was significantly higher than that in the parts above the ground(P<0.05),which was 5.66 mg/kg~41.30 mg/kg.And the cadmium content in the fruits was the lowest,which was 1.47 mg/kg~11.48 mg/kg.The lead absorption of quinoa decreased with the increase of cadmium concentrations in soil,and the total lead content decreased from 9.12 mg/kg to 3.17 mg/kg.Lead and cadmium treatmentscould affect the nutritional qualities of quinoa: 20 mg/kg of cadmium treatment could significantly reduce the protein content of quinoa(P<0.05),but the protein content was not affected by lead concentrations in soil;Lead treatment at 250 mg/kg and cadmium treatment at 20 mg/kg significantly reduced the levels of total flavonoids in quinoa(P<0.05).The antioxidant capacity of quinoa decreased with the increase of lead and cadmium concentrations in soil.(3)Peeling and cooking could effectively reduce the level of lead in quinoa(P<0.05),but couldn't reduce the level of cadmium.After shucking,the lead content in the grains was 52.78?g/kg,which was significantly lower than that in the shells(395.24 ?g/kg).The content of lead in the cooked fruits decreased from 52.78 ?g/kg to 26.94 ?g/kg.Screening could reduce the contents of lead and cadmium at the same time.After 80 mesh screening,the content of lead decreased from 119.84 ?g/kg to 36.12 ?g/kg,and the content of cadmium decreased from67.71 ?g/kg to 53.39 ?g/kg(P<0.05).The lead and cadmium in quinoa could not be reduced by soaking at 20 ?,30 ? and 40 ? for 10 h ~30 h.The lead content in quinoa products was 3.02 ?g/kg~110.20 ?g/kg,and the cadmium content was 11.53 ?g/kg~45.14 ?g/kg,all of which met the requirements of GB 2762-2017(lead ?0.2 mg/kg ?cadmium ?0.1 mg/kg).In summary,this study focused on the selection and production of safe and high-quality processing raw materials for quinoa-related products.Through field experiments,and lead and cadmium stress tests,the distributions of lead and cadmium in quinoa were illustrated,and quinoa's fruit was identified as the part with the lowest contents of heavy metals.18QS-21 was selected as the safest strain with a relatively low concentration of heavy metal.The changes in quinoa qualities were analyzed and it was found out that the presence of lead and cadmium would affect quinoa qualities.At the same time,the effect that different processing methods had on the levels of lead and cadmium in quinoa was investigated.It was found out that 80 mesh sieve could simultaneously reduce lead and cadmium in quinoa.Finally,the contents of lead and cadmium in quinoa products were compared and analyzed,and the results showed that the selected quinoa products on the market contained a safe amount of heavy metals.The results had implications for the safety of heavy metals in quinoa and provided references for the selection of raw materials and safe processing of quinoa.