| Selenium(Se)is an essential trace element in the human body.It has important physiological functions such as enhancement of immunity,anti-cancer and anti-oxidation.Se has important significance for human health.During the process of plant growth,se is applied exogenously.The plant can convert the applied exogenous se into organic compounds containing se in the plant through its own biological metabolism.Se of plants is mainly organic se,such as protein se and polysaccharide se.In this study,se-enriched rice was used as a research object to study the effect on the physiological characteristics of rice growth and its enrichment effect on se.Inductively coupled plasma mass spectrometry(ICP-Ms)was used to quantitatively analyze nutrient elements in se-enriched rice.Se-enriched organics in se-enriched rice were studied using high-performance liquid chromatography-mass spectrometry(HPLC-Ms).The results are as follows:Se was applicated on rice leaves in the range of 10-200 mg/L.As the concentration of se continues to increase,rice grows better.However,reaching the high concentration of se was a growing phenomenon of rice poisoning.And the yield of rice rose first and then decreased.So it shows that the appropriate amount of se could promote the increase of rice biomass,indicated that rice has a better enrichment effect on se.In this study,the se content in se-enriched rice was determined by HG-AFS.The effects of different digestion conditions on se-enriched rice were studied.The se content in rice ranged from 107.1 ?g/kg to 852.9 ?g/kg.Se content in se-enriched rice husk was in the range of 287.6 ?g/kg to 1991.9 ?g/kg.The se content in leaves was 196.7 ?g/kg to 1070.4 ?g/kg.Therefore,se content of stems> se content of leaves> se content of grains.The results showed that the best microwave digestion conditions were the first step: temperature was 100 °C,heating time was 5 min,constant temperature time was 5min,power was 6 W;second step: temperature was 120 °C,heating time was 5min,constant temperature time was 10 min,power was 6 W.In the linear range of 0-50 ?g/L,the detection limit of this method was 0.97 g/L.The relative standard deviation(n=10)was 2.54%,and the recovery rate was 6.1%-101.1%.NaOH,HCl,Tris-HCl,NaCl and the ultra-pure water were used as extractants to extract the dissolved se from the se-enriched rice and determine its content.The distribution law of the dissolved se was: alkali soluble> acid soluble> salt soluble> Tris-HCl soluble> water soluble.It showed that se in rice existed mainly in the form of macromolecule organic se.The extraction of soluble protein from se-enriched rice was studied by the method of alkali extraction and acid precipitation.The effects of alkali concentration,solid-liquid ratio,extraction time,extraction temperature and isoelectric point on the protein extraction rate of rice were determined.The extraction conditions were as follows: extraction solution concentration was 0.15 mol/L NaOH solution,solid-liquid ratio was 1:40,extraction temperature was 40 °C,extraction time was 120 min and isoelectric point pH was 4.8.The se was determined by microwave digestion-HG-AFS.With the increased of se concentration,the protein content in se-enriched rice first increased and then decreased,and the highest content was 13.68%.The results showed that se content in rice protein increased with the increase of exogenous se concentration,and the maximum concentration reached 126.62 ?g/kg.High concentrations of se can increase the proportion of se in total se in the protein.The single factor experiment was used to optimize the extraction of soluble polysaccharides in se-enriched rice.The effects of solid-liquid ratio,extraction time,and extraction temperature on the extraction rate of rice polysaccharides were studied.The results showed that the optimal extraction conditions were: ratio of liquid to solid was 1:40.The extraction time was 120 min and the extraction temperature was 80 °C.The se was also determined by microwave digestion-HG-AFS.The results showed that the polysaccharide content in se-enriched rice first increased and then decreased with the increase of se concentration,and the highest content was 7.74%.When the application of se was 200 mg/L,the highest se content was 42.35 ?g/kg.With the increase of se content in rice,the ability of rice polysaccharides to bind se increased accordingly,and se content of se-enriched rice was significantly lower than that of protein se.The quantification of eight nutrient elements in se-enriched rice samples by ICP-MS was performed.The results showed that the nutrient elements in different concentrations showed different trends.With the increase of se concentration,the contents of Mg,P,S,Fe and Zn increased.The content of B and Mn in rice showed a trend of increased first and then decreased.The content of B reached the highest at 56.47 ng/kg when the se concentration was 40 ?g/L.When the se concentration was 60 ?g/L,the highest concentration of Zn was 89.18 ng/kg,and there was no significant change in Cu content in rice.Thus,choosing se-enriched rice can not only increase the se content of the diet,but also increase the content of other nutrients.Se amino acids in se-enriched rice were prepared by enzymatic hydrolysis.The selenomethionine,selenocystine,and selenium methylselenocysteine were qualitatively analyzed by HPLC-MS.The MRM mode was monitored.The results showed that the content of Se-Cys was in the range of 106.51 ?g/kg to 108.81 ?g/kg,and the content of Se-Met was 110.58 ?g/kg to 113.68 ?g/kg.Se-MeSeCys content was in the range of 157.57 ?g/kg to 160.08 ?g/kg.Therefore,se-enriched rice can be used as an important dietary source for human intake of seleno-amino acids. |
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