| Soil natural Se content and Se form,the Se-enriched mechanism and migration of different crops(rice and soybean)were studied.In addition,the effect of soil Se content on the nutrient composition of crops,the effect of processing on Se content and morphological changes of crops,and the safety evaluation of Se-enriched soybean protein peptide were also analysed,aimed at soil planting rice(paddy fields,primarily protein and starch)and soybean(upland,primarily protein and fat)in different areas containing Se from Fengcheng City of Jiangxi Province,which was known as China's ecological selenium valley.The main conclusions are as follows:(1)Determined the nature of soil in the area of "eco-selenium" in Fengcheng City,Jiangxi Province,the distribution of Se in different plants tissues(roots,stems,leaves and seeds)and the effects on other heavy metals enrichment in rice and soybean growing process.By analyzing the Se forms in paddy fields and dryland soils in different areas of Fengcheng City,it was found that the water-soluble Se content in the soil of Dongjia cun(C area)was 10 times that of Jiaokeng cun(A area),and the contents of acid-soluble Se,exchangeable Se and organic-Se of Dongjia cun(C area)were much higher than that of Jiaokeng cun(A area).These four forms of Se can be directly or indirectly absorbed by plants,it resulting that there was a significant difference in Se content of product in the two region.From seedling stage to panicle development stage,the Se contents in root,stem and leaf increased with the growth of rice,such as the Se content in stem of rice was 0.104 mg/kg(seedling stage),0.174 mg/kg(turning green stage),0.192 mg/kg(tillering stage)and 0.199 mg/kg(pregnancy stage),respectively.But the Se content in the roots,stems and leaves decreased with the growth of rice from the flowering stage to the fruit ripening stage,and the Se content in the stems was 0.174 mg/kg(flowering stage)and 0.156 mg/kg(fruit ripening stage),respectively.The migration of Se during soybean growth period is similar to that of rice.The trend of Se transport in natural Se-enriched soil is transferred from the high Se-containing soil to the non-edible part(roots,stems and leaves)of plants(rice and soybean),and then migrate to plant fruits(rice and soybean).In the Se concentration gradient,the Se content in soil> in root,stem and leaf of plant > in fruit of plant.The contents of Cd and Pb in the leaves were positively correlated with the rice growth period,for example,the Cd and Pb contents in the tillering stage of rice in A area soil were 2.158 mg/kg and 6.897 mg/kg,respectively,but the Cd and Pb contents increased to 3.787 mg/kg and 7.158 mg/kg,respectively,with the growth to pregnancy stage.But the Cd and Pb content in the leaves of rice in the high-Se area(C area)was lower than that in the low-Se(A area)in the same growing period of rice.For example,the Cd content in the A and C areas were 1.574 mg/kg and 1.412 mg/kg,respectively in the turning green stage of rice.At the same time,the study shows that the accumulation rate of Cd and Pb in the high-Searea is slower than that in the low-Searea(A area)during the whole growth period.The results indicated that the amount of Se concentrations had a certain antagonistic effect on heavy metals of Cd and Pb in the process of rice growth.(2)With the increase of Se content in the natural Se-enrichment soilin different Se content soil(low,medium and high Se soil),the increase rate of Se content in the rice and rice bran was higher than the accumulation rate in the rice husk.There were some changes in the 1000-grain weight of natural Se-enriched rice and soybean in different regions,but there was no significant difference between the test groups.The nutritious quality of rice and soybean grain changes,the protein content in the C area was significantly higher than that in the A area,and the protein content increased from 6.61%(A area)to 7.23%(C area),and the content of soybean protein in the C area was higher than that of A area,but the fatty acids content decreased in the C area,which decreased from 18.90% to 16.52%.The effects of different Se contents on molecular weight distribution of soybean protein showed that the difference in Se content did not change the type and molecular weight of the protein,but had a certain effect on the four-stage structure of soybean protein.According to the FT-IR spectra,it was found that there was no obvious absorption peak for soybean protein containing low Se concentration.However,several peaks was observed for the Se-enriched soybean(C region)protein in high Se region.The typical peak at 601cm-1 and 636 cm-1 can be attributed to the stretching vibration of C=Se,and the intense peak at 551cm-1 belonged to the stretching vibration of C-Se.Two characteristic peaks were found at 830cm-1 and 2258cm-1,which can be assigned to the stretching vibration of Se=O and bending vibration of Se-H.The effects of different Se contents on protein composition and amino acid composition of soybean suggested that the soybean protein subunit composition was changed in different Se content(SDS-PAGE)spectra showed strip did not increase,nor did it decrease,and the molecular weight of the protein ranged from 100-600.0 k Da,the amino acid composition has a certain impact.The Se content was higher in the soil,the cysteine(Cys)and methionine(Met)content was lower.The cysteine content in the low-Seeara(A eara)was 0.682%,but it was only 0.102% in the high Se eara(C eara)in rice protein.With the different Se content in soil,the results showed that the composition of fatty acids in soybean oil changed,the ratio of hexadecanoic acid,heptadecanoic acid,eicosanoic acid and docosanoic acid in soybean oil did not change significantly.However,the ratio of palmitic acid and stearic acid increased,while the proportion of linoleic acid and linolenic acid decreased with the increase of Se content.(3)0.1 mol/L Na OH was applied for extraction of Se protein in soybean,the protein yield and Se content are the highest,which were 55.75%and49.55mg/kg respectively,it indicating that the alkali extraction of Se-enriched soybean protein had high efficiency.Optimum processing parameters of Se-enriched soybean protein by orthogonal method were as follows: p H10.5,extraction temperature 55?,extraction time 60 min,liquid ratio 14: 1,it showed that the protein extraction ratewas 87.58% and the Se content was 53.78 mg/kg.Optimum processing parameters of Se-enriched soybean protein peptide by orthogonal method were as follows:the enzymatic hydrolysis time 80 min,the liquid to solid ratio 10: 1,the reaction temperature 50 ?,the amount of enzyme 0.4%,the enzymolysis rate was 72.2%,the purity of protein peptide was 89.8%,the Se content was 94.65 mg/kg.When the enzymolysis solution was carried out by the ultrafiltration technology,the yield of the polypeptide was 78.18% and the Se content was 125.70 mg/kg.Effects of different Se contents soybean protein on ·OH,O2-·and DPPH were studied,the results showed that with the increase of protein concentration(0.2~0.6 mg/m L),the clearance rates of ·OH increased.At the concentration of 0.6 mg/m L,·OH clearance rates of high-Se soybean protein(C area),ascorbic acid,BHT(2,6-di-tert-butyl-4-methylphenol)and low-Se soybean protein(A area)were 48.7%,85.5%,26.5% and 8.62%,respectively,it indicating that Se plays an important role the removal of ·OH.When the sample concentration was 1.0 mg/m L,the scavenging rates of O2-·were 22.52% and 5.24%,respectively between high-Se soybean protein(C area)and low-Se soybean protein(A area),due to the differen Se content,the scavenging rates of O2-· was three times that of the low-Searea(A area).(4)With the increase of extrusion temperature,the amount of water loss in puffed rice flour increased,the precipitation rate of puffed rice flour decrea sed,the dissolution rate and precipitation water absorption increased,and there was significant difference.The water-soluble sugar content was the lowest when the extrusion temperature was 140-150 ?.When the temperature rose to 160 ?,the content of water-soluble sugar increased from 36.4% to 38.1%.The composition of rice protein was changed before and after extrusion,and there was no band with a molecular weight of 85.0 k D in the non-puffed selenium-rich rice protein,but there was a 25.0 k D band.The protein composition of the extruded rice flour did not change significantly in the different temperature sections of the extruded rice.The water absorption,water holding capacity and foaming property of the protein in the extruded rice flour were higher than those of the unexpanded extruded rice protein,and increased with the increase of the puffing temperature,but the oil absorption was the opposite trend that it was lower than that of the unextruded rice protein(E)and with the temperature,protein oil absorption becomes smaller.The angle of repose and the angle of slippage of puffed rice tend to increase,and they increased with the increase of mesh number.SEM microstructures show that unexpanded rice particles have a rough surface,combined with evacuation,and are not uniform in size.For extruded puffed rice flour,the surface becomes smooth,the internal cavity significantly increased,evenly distributed,loose tissue,similar to the porous sponge-like structure.However,when the temperature exceeds 170 ?,the surface cracks,and as the temperature rises further,the more obvious the fissure.The X-ray showed that the high-order microcrystalline zone of the X-ray diffraction line in the non-puffed selenium-enriched rice is significantly larger than that after the puffing,and it was no obvious that the X-ray diffraction curve of the puffed rice flour varied with different temperature range.(5)The safety toxicological evaluation of natural Se-enriched soybean protein hydrolyzate showed that LD50 was more than 20 g/kg · bw,and no mutagenicity was found in Ames test and micronucleus test.The results of the 30 d feeding test showed that the animals did not appear to be antifeedant during the experiment.The animals were normal,densely and shiny,indicating that the natural selenium-rich soybean protein peptide had good food safety.The effect of tumor growth on mice was also studied.The results showed that the Se-enriched soybean protein peptide significantly inhibited tumor growth(80.2%),prolonged the life span of infected mice for 3~5 days,and had a positive effect on tumor adjuvant therapy.If normal serum supplemented with Se-enriched soybean protein peptide(202.50?g/kg dose),serum GPX activity increased by 1.2 times,and serum LPO content showed a downward trend,suggesting a dose-dependent.For tumor-bearing mice,the serum GPX activity increased by 1.5 times and the serum LPO content decreased with the increase of the Se-enriched soybean protein peptide replenishment dose.In the immune function of mice,supplemented with Se-enriched soybean protein peptide can promote immune organs,especially thymus development,and enhance immune regulation in the range of 202.50?g/kg dose.On the S180 tumor cell morphology,it was revealed that with the Se-enriched soybean protein peptide concentration increased,the cells gradually shrinkage smaller,cell shrinkage,increased cytoplasmic particles,a large number of cell fragmentation,and ultimately lead to apoptosis,indicating that Se-enriched soybean peptide had significant anti-tumor effect. |
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