Application of different techniques to identify the effects of irradiation on Brazilian beans after six months storage

Four different techniques to detect the effect of irradiation in beans were investigated. Two types of Brazilian beans, Phaseolus vulgaris L., var. carioca and Vigna unguiculata (L.) Walp, var. macaçar, were irradiated using a ⁶⁰Co source with doses ranging from 10.0 kGy. After 6 months storage at ambient temperature the detection tests were carried out. Firstly, germination tests showed markedly reduced root growth and almost totally retarded shoot elongation of irradiated beans as compared to non-irradiated beans. Secondly, DNA fragmentation was studied using a microgel electrophoresis. Irradiated cells produced typical comets with DNA fragments migrating towards the anode. DNA of non-irradiated cells exhibited a limited migration. Thirdly, electron spin resonance for detection of cellulose radicals was tested, since it was expected that these free radicals are quite stable in solid and dry foods. However, only in beans irradiated with 10 kGy a small signal could be detected. Fourtly, thermoluminescence, a method to analyze mineral debris adhering to food, turned out to be a good choice to detect irradiation effects in beans, even after 6 months of storage. The results indicate that three of these four techniques proposed, can be used to detect the effect of irradiation in these two varieties of Brazilian beans at a dose level useful for insect disinfestation (1 kGy).     

Analysis of Low Molecular Weight Carbohydrates in Food and Beverages: A Review

This review presents a study of new advances in chromatographic methods and capillary electrophoresis for the analysis and quantification of carbohydrates in food and drink that have been made in essentially the last seven years (1995–2002). All the main groups of sugars have been considered: monosaccharides, disaccharides, trisaccharides, oligosaccharides, related compounds such as alditols, alditol glycosides, polyols, amino sugars, deoxy sugars, uronic acids and aldonic acids. The chromatographic methods referred to are High Performance Liquid Chromatography (HPLC), Gas Chromatography (GC) and related techniques (AMD-HPTLC: High Performance Thin-Layer Chromatography with Automated Multiple Development). Capillary Electrophoresis (CE) was also discussed.     

The surface composition of spray-dried protein—lactose powders

The surface composition of spray-dried mixtures of lactose-protein and lactose-glycine were estimated by means of electron spectroscopy for chemical analysis (ESCA). The results show that even with a low concentration of protein (0.01 wt.%) in the solution to be dried, protein starts to appear on the surface of the powder. At a protein/lactose ratio of 1/99 the protein starts to dominate the powder surface. At a protein/lactose ratio of 20/80, about 70% of the surface is covered by protein. The results are similar for the proteins sodium caseinate and bovine albumin.

The spray drying of mixtures of lactose and glycine gives a different result. In this case, the surface composition of the powder reflects the composition of the mixture to be dried.

The surface tensions of the solutions show that the proteins have a higher surface activity than lactose, since even a small amount of protein added to a lactose solution lowers the surface tension considerably. Glycine affects the surface tension only to a minor extent.

These results show that the composition of the air-water interface of the drying droplets is reflected in the surface composition of the dried powder. In addition, scanning electron micrographs show that the changes in the powder structure when protein is added to the solution are associated with the presence of protein on the surface. When the surface coverage of protein increases, dents start to appear in the particles. The powders made from lactose-glycine solutions are highly agglomerated regardless of the glycine concentration.     

On-line coupling of flow injection displacement sorption preconcentration to high-performance liquid chromatography for speciation analysis of mercury in seafood

A simple and cost-effective method for speciation analysis of trace mercury in seafood was developed by on-line coupling flow injection microcolumn displacement sorption preconcentration to high-performance liquid chromatography (HPLC) with UV detection. The methodology involved the presorption of the Cu-PDC (pyrrolidine dithiocarbamate) chelate onto a microcolumn packed with a cigarette filter sorbent, simultaneous preconcentration of Hg(II), methylmercury (MeHg), ethylmercury (EtHg), and phenylmercury (PhHg) onto the microcolumn through a displacement reaction with the presorbed Cu-PDC, and their subsequent elution from the microcolumn for on-line HPLC separation. Interferences from heavy metal ions with lower stability of their PDC chelates relative to Cu-PDC were minimized without the need of any masking agents. With the consumption of 4.0 ml of sample solution, the enrichment factors were about 80. The detection limits were 10-25 ng g(-1) (as Hg) in fresh tissue. Precision (R.S.D. (%), n = 5) ranged from 2 to 3% at the 500 microg l(-1) (as Hg) level. The developed technique was validated by analyzing a certified reference material (DORM-2, dogfish-muscle), and was shown to be useful for mercury speciation in real seafood samples.     

New food control system in Japan and food analysis at NFRI

In Japan, there was a drastic change in food control system, which was brought about by problems with BSE. Food Safety Basic Law was newly enacted and Food Hygiene Law, Japanese Agricultural Standards Law and so on were revised. Food Safety Commission was newly established for risk assessment, and Ministry of Agriculture, Forestry and Fisheries and Ministry of Health, Labor and Welfare were reorganized on food safety. National Food Research Institute (NFRI) works for improvement of technology for food analysis, development of technology to ensure food safety and so on. Objects of food analysis are inorganic elements, acrylamide, mycotoxins, functional components, genetically modified organisms, varieties of rice and so on. Proficiency testing schemes (PTs) were introduced to NFRI for reliability of food analysis. Certified reference materials (CRMs) of food related materials prepared in Japan, and PTs provided by Japanese organization were limited. It is requested for Japanese organizations to prepare new CRMs and provide many kinds of PTs for solution of peculiar problems.     

Simultaneous determination of PCDDs, PCDFs, PCBs and PBDEs in food

Established and comprehensively validated methodology for the analysis of PCDDs, PCDFs and polychlorinated biphenyls (PCBs) in food, animal feed and other matrices is presented. The method achieves the analytical standards of EU protocols (2002/69/EC and 2002/70/EC) that are used to determine the compliance of food and animal feed to maximum permissible levels of chlorinated dioxins in these commodities. The methodology provides WHO–TEQ data for dioxins and PCBs as well as individual concentrations for toxic PCDD/F congeners and >50 commonly occurring PCBs. In addition, the methodology allows the simultaneous determination of individual polybrominated diphenylether (PBDE) congeners. A wide range of ¹³Carbon-labelled surrogates allow accurate internal standardisation, and measurements are carried out using high resolution GC coupled to high resolution mass spectrometry except for mono-, tetra, ortho-substituted PCBs where unit resolution mass spectrometry can be used instead. Evidence of internal as well as external validation through the frequent use of reference materials, and successful participation in international inter-comparison exercises over many years is presented. A large number of different food types have been analysed for dioxins and PCBs using this methodology over several years and typical congener profiles for various food matrices are discussed.     

ICP-MS同时测定植物性食品中稀土元素的方法研究

建立了植物性食品中16种稀土杂质(Sc、Y、La、Ce、Pr、Nd、Sm、Eu、Gd、Tb、Dy、Ho、Er、Tm、Yb和Lu)元素的电感耦合等离子体质谱(ICP-MS)的分析方法.考察了基体效应及质谱干扰,应用In内标,有效地补偿基体效应所引起的测量偏差,建立修正公式校正质谱干扰.对照分析了参考标准物质.对所测定元素,校正曲线的相关系数为＞0.9990,方法的检出限低于2.2 pg/g(Sc为95pg/g),回收率为92%～106%,RSD优于3.2%(n=7).     

微乳液增敏邻硝基苯基荧光酮光度法测定食品中痕量铅

本文研究了在微乳液介质中,pH=10.0时,铅与邻硝基苯基荧光酮(o NPF)显色生成稳定的1∶3配合物,在598nm处摩尔吸光系数为8.74×104L·mol-1·cm-1,铅含量在0～1.2μg/mL范围内符合比耳定律。采用巯基葡聚糖凝胶分离富集,消除了共存离子的干扰。用所拟方法测定食品中的微量铅,结果令人满意。     

皮革固体废弃物的高值转化

传统的制革工业在生产过程中要产生原皮重60%以上的固体废弃物，由于没有充分利用，成为造成制革工业污染严重的重要原因之一，随着资源，环境等全球性生态问题的日益严峻，制革废弃物的资源化，特别是高值转化，已成为国内外关注的重要课题，本文对作为天然的生物质资源的胶原适用于食品，医药和人妆品的属性及其应用以及从制革皮边角废弃物中提取胶原的方法作了简要论述。     

HPLC-ESI-MS analysis of Vitamin B12 in food products and in multivitamins-multimineral tablets

Methods for the determination of Vitamin B₁₂ remain limited due to their low sensitivity and poor selectivity. In the present work, a simple and sensitive HPLC-ESI-MS method for determining Vitamin B₁₂ in food products and in multivitamin-multimineral tablets was developed. Vitamin B₁₂ was extracted from food products with 50 mM sodium acetate buffer (pH 4.0) in the presence of sodium cyanide. Total Vitamin B₁₂ content in food product can be obtained by efficient enzymatic hydrolysis to release the bound Vitamin B₁₂. Vitamin B₁₂ was quantified with ginsenoside Re as internal standard (I.S.) after their separations on a C₁₈ column with a gradient of mobile phase made of water and acetonitrile. MS with SIR mode at m/z 930.8 was used for Vitamin B₁₂ quantification. The calibration graphs plotted with five concentrations of Vitamin B₁₂ was linear with a regression coefficient r² = 0.9994. The intra-assay R.S.D. and the inter-assay R.S.D. were 2.6% (n = 5) and 3.5% (n = 6), respectively. The recoveries evaluated at spiking three different concentrations on fortified products were above 93%. The method has been applied successfully in the determination of Vitamin B₁₂ in fortified food products and multivitamin-multimineral tablets.