| With the increasingly serious cadmium pollution in environment,cadmium pollution in rice gradually appears.Rice is staple food for more than 60% population in our country,so it is very important to determinate cadmium content and evaluate safety of rice in our country.At present,there are a large number of cadmium polluted rice being destroyed for illegal in Food Safety Law of our country.Therefore,it has important social benefits and economic benefits to research the rational use of cadmium polluted rice,because it not only can promote the development of rice processing industry in our country,but also can maximize the use of abandoned rice resources.To conduct a comprehensive investigation on cadmium pollution levels of rice in our country,we collected 507 rice samples from 15 provinces in the main breadbasket.Cadmium was detected by microwave digestion and atomic absorption spectroscopy,and the detection rate is 94.67%.In general,the range of cadmium content in the main breadbasket is <LOD-0.8431mg/kg,the mean value is 0.0092mg/kg,the median is 0.0624mg/kg,which is far below the national limit for cadmium(0.2mg/kg),and the over-limit ratio is 10.65%.According to the data of cadmium content,we can calculate the monthly cadmium intake of residents in our country from rice,the value is 1.1783?g/(kg·bw),which accounts 4.71% of the value of PTWI recommend by WHO.We can draw the conclusion that it is basically safe to intake rice of the main breadbasket in our country.Comparing different regions,we can see that cadmium pollution in south is more serious than the north.Hunan province has the most serious cadmium pollution in rice,the mean value of cadmium content is 0.3334mg/kg,and the over-limit ratio is 72.50%.Whereas cadmium content of rice in Jilin is the lowest,the mean value is 0.0046mg/kg,and no over-limit sample is detected.In order to explore the cadmium distribution in rice and then to provide a reference for utilizing rice polluted by cadmium,we selected 76 rice samples of different pollution level for research.Four processed products were acquired by milling and grinding.The results show that the cadmium concentration order is rice bran(0.5044mg/kg)> brown rice(0.2405mg/kg)> original rice(0.2123mg/kg)> white rice(0.2101mg/kg)> glume shell(0.1170mg/kg),and the cadmium cumulant rate order is brown rice(84.13%)> rice(66.83%)> rice bran(19.16%)> glume shell(13.40%).Cadmium concentration of glume shell reduced by 39.19% compared to original rice,and cadmium content of most glume shell is lower than the nation limit,so it can be utilized directly without extra processing.But the cadmium concentration of most white rice and rice bran is still over-limit,so they both need further processing.Take a indica rice in Hunan province as the raw material,extract rice peptide with low cadmium content from white rice.The cadmium concentration of the white rice is 0.5503mg/kg.Firstly,extract rice protein from the white rice in alkaline solution.The result shows that the yield rate of rice protein from white rice is 51.69%,the purity is 85.81%,the extraction rate is 44.36%,the concentration of cadmium is 2.1148mg/kg.Secondly,digest the rice protein with alkaline protease and trypsin;thirdly,ultrafilter the enzymatic hydrolysate by using the ultrafiltration membrane with 3000 Da intercept molecular weight;then,desalinate the crude peptide by resins DA201-C,and the rice peptide is finally acquired.Its yield rate is 1.13%,the purity rate is 88.68%,the concentration of cadmium is 0.0052mg/kg,which is reduced by 99.06% compared to white rice.Take indica rice in Hunan province as the raw material,extract rice bran oil with low cadmium content from the rice bran.The cadmium concentration of the rice bran is 0.7795mg/kg.Extract the rice bran oil by using hexyl hydride(solid-liquid ratio 1:5,4h,40?).The result shows that the yield rate is 15.90%,the concentration of cadmium is 0.0584mg/kg,which is reduced by 92.51% compared to the rice bran. |
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