Determination of elemental concentration profiles in tender wheatgrass (Triticum aestivum L.) using instrumental neutron activation analysis

Samples of shoots and roots of tender wheatgrass/wheat plants collected over a period of 20 days were analysed by instrumental neutron activation analysis. The wheatgrass (wheat: Triticum aestivum L.) samples analysed were grown in three different conditions namely (i) tap water, (ii) nutrient compounds with tap water, and (iii) soil and tap water. A total of 15 elements were determined in these samples. In addition, a commercially available wheatgrass tablet was analysed. Accuracy of the method was evaluated by analysing two biological reference materials, SRM 1573a (Tomato leaves) from NIST and ICHTJ-CTA-vtl-2 (Tobacco leaves) from INCT. The paper discusses the elemental concentration levels, their trends and concentration ratios of elements in shoot-to-root grown in these three conditions of growth. It was observed that the elements such as K, Na, Ca and Mg increased linearly in the shoots with the growth period whereas the concentrations of the elements namely Zn, Mn and Fe remained constant in shoots after 8th day of plant growth for all three conditions of growth. However, it was observed that the shoot to root concentration ratio in all the conditions increased linearly for K, Na, Ca, Mg and Cl and decreased for Zn, Fe, Mn, and Al with growth period.     

Determination of mineral element composition of Ayoyo,Baobab and Dandelion vegetable green leaves in Ghana using instrumental neutron activation analysis

The present investigation was undertaken to determine the nutritional compositions (mineral elements) of three green leafy vegetable; Dandelion (Taraxacum Officinale), Ayoyo (Corchorus Olitorius) and Baobab (Adasonia Digitata). The ultimate goal is to improve nutrition and health by advocating for increased consumption of indigenous green leafy vegetables with an objective to increasing public acceptance, awareness and utilization. The mineral elements were determined using instrumental neutron activation analysis, over 20 elements were detected. However, 14 mineral elements were quantitatively evaluated on the basis of k₀-method and relative comparator method. The leaves were characterized with high concentration of Mg, Ca, Cl and K, and substantive amount of Mn, Fe, Zn, Cu and I. The composition of the mineral elements and its respective percent contribution to Recommended Dietary Allowance/Adequate Intake (RDA/AI) for various life groups indicates that reasonable consumption of any of the three green leafy vegetable can contribute substantive amount of daily nutritional requirement for minor nutrients like; I, Cu, Zn, Mn, and Fe as well as major nutritional (Mg, Ca, Cl and K) needs for all life groups. Each of the leaves was also characterize with high K/Na ratios. Tolerable upper intake levels (UL) analysis also showed no significant abuse for the mineral elements determined. Other potential toxic elements (As, Cd and Hg) and non-nutritional minerals (Br, V, Al and Ba) were either not detected or were found in low concentrations.     

Characterization and quantification of engineered nanoparticles in food by epithermal instrumental neutron activation analysis and electron microscopy

Engineered nanoparticles (NPs) have increasingly been used in various areas including agriculture and food packaging, which may potentially cause contamination in food products. In this study, a combination of analytical techniques was used to detect, characterize, and quantify engineered NPs (cerium (IV) oxide (CeO₂), silica (SiO₂) NPs, and their mixture) in food matrices. A series of concentrations of CeO₂, SiO₂, and their mixtures from 0 to 0.75 wt% were mixed in soybean powders. The presence of engineered NPs was investigated using transmission electron microscopy and scanning electron microscopy coupled with energy dispersive spectroscopy. The average size of CeO₂ and SiO₂ was 28.5 and 30.5 nm in diameter, respectively. CeO₂ NPs were irregular octahedral and cubic in shape, while SiO₂ NPs were spherical. The concentration of NPs in soybean powders was analyzed by epithermal instrumental neutron activation analysis (EINAA). Calibration curves were plotted for quantification of NPs in soybean powders (R ² = 0.996 and 0.994 for CeO₂, SiO₂ NPs in soybean powders, respectively; R ² = 0.995 and 0.997 for CeO₂ and SiO₂ NP in a mixture in soybean powders, respectively). The study of the detection limit (DL) demonstrates that at 99 % confidence interval, EINAA can detect both NPs at 0.1 wt% in soybean powders. Satisfactory recoveries were obtained for samples with a concentration at and higher than the DL (86.2–104.7 % for CeO₂ NPs and 85.7–95.2 % for SiO₂ NPs; 87.5–101.3 and 85.6–93.5 % for CeO₂ and SiO₂ NPs in a mixture in soybean powders, respectively).     

Determination of silver in foods by neutron activation analysis

Silver has been determined in a number of foodstuffs by neutron activation analysis. The results range from <1 to 530 ng g^?1 dry matter and are highly variable, suggesting that random contanination of samples may occur. Higher concentrations of up to 31 ug g^?1 dry matter were found in wild fungi. From these results, supplemented by others, the British dietary intake is estimated to be 4.5 ug Ag day^?1, which constitutes no hazard to human health.     

微型核反应堆超热中子活化分析食品中的微量砷

为提高食品中微量砷的检测能力 ,利用在微型核反应堆安装的超热辐射孔道对样品进行照射降低样品的本底值后测定食品中的微量砷。方法的检出限为 6 7× 10 -9g ,RSD =4 3% ,样品的回收率在 98%以上。微型核反应堆超热中子活化分析法可用于食品中微量砷的检测。     

Trace mineral content of Argentinean raw propolis by neutron activation analysis (NAA): Assessment of geographical provenance by chemometrics

Multielement analysis of raw propolis samples, collected from different central Argentinean regions, was carried out by Neutron Activation Analysis (NAA) aiming at developing a reliable method in their traceability. This work presents a characterization of 96 raw propolis samples selected from three different geographical origins in middle region of Argentina. Multivariate chemometric techniques, such as Principal Component Analysis (PCA), were applied to perform a preliminary study of the data structure. Two supervised pattern recognition procedures including stepwise linear discriminant analysis (LDA) and K-nearest neighbors (kNN) were used to classify samples into the three categories considered on the basis of the chemical data. Eight trace elements (Br, Co, Cr, Fe, Rb, Sb, Sm and Zn) were selected by stepwise-LDA explaining the classification of propolis according to their geographical origin. Application of k-nearest neighbor classification procedure to these eight selected variables produced a good correlation (98% correct classification ratio) of propolis with its provenance. The trace element profiles provided sufficient information to develop classification rules for propolis identification according to their provenance.     

Applicability of neutron activation analysis (NAA) in quantitative determination of some essential and toxic trace elements in food articles

Accurate and reliable data on microgram and nanogram quantities of some essential and toxic elements in most food articles are very scarce. Neutron activation analysis (NAA), with its essentially blankfree advantage, is a valuable approach in the field of determination of trace elements in different foodstuffs and diets. Accordingly, various radiochemical (RNAA) and instrumental (INAA) approaches have been developed in our laboratory for the elements As, Cd, Co, Cu, Hg, I, Mo, Ni, Sb, Se, Sn, Th, U, V, and others, and verified by the analysis of compositionally appropriate certified reference materials.This communication was presented as a poster at EURO FOOD CHEM VIII, Vienna, September 18–20, 1995, and was one of three such posters which were awarded as being outstanding     

Texture and color analysis of freeze-dried potato (cv. Spunta) using instrumental and image analysis techniques

Most typical approaches for measuring color and texture properties are time consuming. An image-based method was used to evaluate the texture and color in freeze-dried potatoes. Microstructure of cooked, cooked freeze-dried and rehydrated potatoes were analyzed by scanning electron microscopy. Texture properties were analyzed by a texture analyzer and image analysis. Color was determined with a spectrocolorimeter and a digital camera. Significant differences (p < 0.05) were obtained for cooked and cooked freeze-dried rehydrated potatoes. A linear trend was applied for instrumental and image features for texture and color values. Results showed that texture features of images, such as contrast, entropy, energy, and homogeneity (calculated from grey level co-occurrence matrix), showed correlations with instrumental texture features, such as hardness, adhesiveness, chewiness, cohesiveness, and resilience. Similar results were also obtained for color features. This study showed that image processing techniques could be applied as a useful tool to analyze quality in potatoes.     

木霉的RAPD分析

运用随机扩增多态性DNA(RAPD)技术对18个木霉菌株进行基因组DNA多态性分析.扩增结果表明,18个引物均反映出18个菌株间的遗传多态性,供试18个木霉菌株的RAPD分析与其生防效果之间不存在相关性.引物OPA-04与OPA-13对木霉菌全基因组DNA具有特征性分子标记.聚类分析结果表明,种间的聚类分析结果与形态鉴定的结果趋于一致.以欧氏距离5.0～5.5为适宜的阀值范围,RAPD遗传标记木霉菌可以作为该菌分类的有效手段之一.     

Determination of major and minor elements in dairy products through inductively coupled plasma optical emission spectrometry after wet partial digestion and neutron activation analysis

A wet partial digestion procedure using hydrochloric acid was investigated to determine the concentration of Ca, Cr, Cu, Fe, K, Mg, Mn, Na, P and Zn in dairy products by Inductively Coupled Plasma Optical Emission Spectrometry (ICP OES) technique. The results of this partial digestion were satisfactory and no loss of analytes was observed. A comparison of the results obtained from this methodology was carried out with the other results from dry ashing digestion and Instrumental Neutron Activation Analysis (INAA) technique that do not require pre-treatment procedure.     

微量元素与人体健康

微量元素是构成人体内某些酶、活性蛋白、维生素和激素的不可缺少的重要成分,对机体的代谢和生存有着极其重要的生物学作用。对微量元素的生理功能及其在人体中的代谢过程加以介绍,并就铜、锌、碘、氟、硒等对人体的影响分别进行了简单的论述。     

仪器分析课程教学的思考

针对仪器分析课程特点,提出教学方法、考核形式的改革思路。教学中应综合运用各种教学手段,培养学生实际应用能力;考核中增加平时学习成绩的比重及对学生创新能力的考察,调动学生学习的自觉性、主动性,提高教学效果。     

根霉菌在食品工业中应用的安全性

一些根霉菌种产生毒素使其在发酵食品中的应用安全性受到了质疑.该文从毒素的研究进展和现状出发提出根霉菌可能存在的食品安全问题,并介绍文献资料在毒素研究过程中采用的一些新方法,希望从食品安全角度研究根霉菌的科学应用问题,为我国合理利用根霉菌发酵生产安全的发酵食品奠定基础.     

Rapid detection of Salmonella spp. using magnetic resonance

The globalization of the world's food trade calls for rapid and accurate detection of foodborne pathogens to ensure safety of foods for human consumption, to prevent outbreaks and management of foodborne infectious diseases. Currently, commercial detection methods for pathogenic microbials require multiple days for sample‐to‐answer results. In this study, we demonstrated a highly sensitive and rapid detection of a microbial pathogen using Molecular Mirroring (M²) technology and Lab‐in‐the‐Box system based on nuclear magnetic resonance that works rapidly and efficiently for the detection of Salmonella. This technology detected Salmonella at 1 cfu/reaction in water. In tuna, the M² technology detected 1 cfu/g with 5 hr of enrichment and analysis with a T₂ signal of 342 ms. In addition to sensitive detection and minimal enrichment, this methodology detected pathogens from inhibitory mediums. Therefore, this technology can be widely applied to other fields such as environmental monitoring, public health and safety, national security, and medical diagnosis.

Practical applications

The combination of molecular biology and nuclear magnetic resonance technology represents a novel, rapid, sensitive, and highly specific methodology for the detection of Salmonella spp. in tuna compared to standard conventional methods. Practical applications of the M² technology have been tested with human samples, animal samples, and food samples to detect microbial pathogens before and after food processing, thus is ideal to protect public health and to ensure food safety. Furthermore, this biosensor analytical technology can be applied to almost any medium or target of interest in the field of food safety, clinical diagnostics, and biosurveillance.     

Determination of non-radioactive liquid phase markers,Co-EDTA and Cr-EDTA,by neutron activation analysis

An instrumental neutron activation analysis (INAA) method has been devised which permits rapid and reliable analysis of the liquid phase markers Cr-EDTA and Co-EDTA. Dried rumen fluid samples, containing Cr-EDTA and Co-EDTA, were irradiated in the Slowpoke reactor. The analytical scheme previously devised for solid phase marker ^165mDy determination was found to provide an acceptable compromise between sensitivity and sample throughput (45 samples h^?1) for the short-lived ^60mCo (T_1/2=10.47 min). Cr measurements required longer irradiation cooling and counting times. To permit satisfactory sample throughput, batch sample irradiations and an automated NaI(Tl) scintillation detector was used. Gamma interferences were studied with a high resolution Ge(Li) detector and found to be negligible provided that sufficient decay time is allowed. Detection limits for Co and Cr are presented for the analytical schemes used.     

Measurement of engineered nanoparticles in consumer products by surface-enhanced Raman spectroscopy and neutron activation analysis

There has been an increasing number of consumer and food products sold on the market that contain various engineered nanomaterials (ENMs) such as silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs). These nanomaterials possess novel physical and chemical properties that can be used for wide applications in agriculture and food safety. However, current analytical methods to detect and measure ENMs are time-consuming, labor-intensive, and expensive. The objective of this study was to develop a novel, simple, rapid, and accurate method to detect AgNPs and AuNPs in consumer products using surface-enhanced Raman spectroscopy (SERS). SERS measurement was conducted to detect AgNPs and AuNPs using an effective Raman indicator, 4-aminothiophenol (pATP). The pATP can strongly bind onto nanoparticles, generating greatly enhanced Raman signals that can be used for measurement. The pATP was combined with Ag or Au stock solution, AgNO₃, citrate-coated AgNPs, citrate-coated AuNPs, AuCl, AgNPs, AuNPs, and five commercial products to study the differences in their SERS spectral data. The observed spectra of AgNPs and AuNPs have similar peaks at ~?390, ~?1087, and ~?1590 cm^?1 that can be attributed to the C–S stretching vibration, C–C stretching vibration, and C–H stretching vibration, respectively. Neutron activation analysis (NAA) and electron microscopy was used to characterize and quantify AgNPs and AuNPs in the consumer products. The results demonstrate that SERS method in combination with NAA can be an effective method for detection of ENMs, and it can easily distinguish AgNPs and AuNPs from other non-nanoparticle species in the complex matrices.     

Chemometric differentiation of raw and commercial milk by trace elements using principal component analysis.

Nine trace elements (Cr, Mn, Fe, Ni, Cu, Zn, Mo, Cd, and Pb) were determined in the dissolved ash of 36 samples of raw milk. The distribution of the concentration of each element was first investigated by means of a test of normality. The matrix of the correlation between the concentrations of the elements was then used as a starting matrix for principal component analysis. Nine variables were reduced to four principal components, accounting for 75% of the total variance. The biophilic elements Mn-Fe and Cu-Mo were positively associated with the first two principal components, while Cr was correlated to the third and Ni and Cd with the fourth principal component. Pb and Zn are both negatively correlated to the first principal component. Comparison with 42 samples of a commercial milk, by using a two-dimensional plot of the principal component scores, rendered possible the differentiation between raw and commercial milk.     

豆豉中抗氧化芽孢杆菌的多样性分析和鉴定

从豆豉中分离筛选具有抗氧化能力的芽孢杆菌菌株,以豆粕为原料,以抗氧化性测试为筛选体系,筛选优良菌株并鉴定,了解菌株的抗氧化特性并为功能性成分的开发提供菌株资源。对菌株发酵豆粕上清液,使用DPPH·清除率作为初筛方法获得12株菌株,其清除率在86.2%~96.6%,使用·OH清除率等6种抗氧化评价方法进行复筛并测定多肽浓度,结果显示各抗氧化性测试方法间相关性不明显,仅有总抗氧化力与·OH清除率显著正相关,与·O2-清除率极显著正相关。多肽浓度与各抗氧化性测试方法间无显著正相关,与脂质过氧化抑制率呈极显著负相关,提示12株菌株产生的抗氧化成分在类型和机理可能存在较高的多样性。将菌株发酵上清液密封后在50℃保存14 d,抗氧化力均呈下降趋势,HFBL261菌株抗氧化力残留最高,对其表型形状和16S r DNA序列进行测定,鉴定为Bacillus subtilis。