紫外-可见分光光度法测定烤烟中亚硝酸盐的含量

建立了紫外-可见分光光度法测定烤烟中亚硝酸盐含量的分析检测方法。对提取时的提取液脱色、提取效果、提取液的净化以及测定时提取液的吸取量进行了试验,同时考察了方法的稳定性、精密度和准确度,并用本方法测定了不同烤烟样品中的亚硝酸盐含量。结果表明:该方法操作简单、稳定性好、精密度高、适用范围广,回收率84.8%～98.2%。该方法适用于烤烟中亚硝酸盐含量的测定。     

气相色谱法测定食盐中的碘含量

目的建立气相色谱法测定食盐中碘含量的分析方法。方法在酸性条件下,食盐中的碘在过氧化氢的氧化作用下,与丁酮生成衍生物碘丁酮,气相色谱的分离,电子捕获检测器(election capture detector,ECD)检测。探究衍生剂的用量、衍生时间,并对未加碘食盐和强化碘食盐进行检测及方法间比对。结果在10～120μg/L线性范围内回归系数r=0.9998,检出限为0.002 mg/kg(S/N≥3),定量限为0.006 mg/kg(S/N≥10),相对标准偏差RSD范围为1.5%～3.2%(n=6),加标回收率在91.3%～112.8%之间。与氧化还原滴定法进行方法间比对,单一样本t检验分析无显著性差异。结论该方法操作简单快捷,结果灵敏度高、准确度和精密度好,适用于食盐中碘含量的测定。     

气相色谱法测定白酒功能性成分四甲基吡嗪

建立了用气相色谱法测定白酒中四甲基吡嗪含量的方法,并对3种不同酒样进行检测。该外标法在测定酒样时的标准偏差为0.005～0.058,变异系数为2.83%～9.99%,回收率为86%～106%,具有操作简便快捷、精密度好、准确度高的特点。检测结果表明,不同酒样中的四甲基吡嗪的含量有较大差异,可以据此对白酒品质进行评价。     

大蒜中果聚糖的测定

大蒜是WHO推荐的保健食品,为了正确评价其功能,非常需要测定其多糖的含量。文中根据Seli-wanoff反应提出一个方法,即在酸性条件下,以硫酸铁铵为催化剂,果糖和间苯二酚反应生成橘红色络合物,在473nm下有最大吸光度。结果表明果糖含量在0～182μg范围内标准曲线呈线性,方法的准确度2.6%,精制大蒜测定的精密度为0.52%,一般样品测定的精密度为0.51%～1.62%,回收率为(98.98±0.51)%,并测得山东杂交大蒜、山东白皮大蒜、广西独头大蒜的果聚糖含量分别为13.25%、20.28%、20.96%。此方法操作简单,准确度高,重复性好。     

用毛细管气相色谱分析黄酒中的甜蜜素

建立了毛细管气相色谱分析黄酒中的甜蜜素的方法。先使样品通过沸水浴蒸发干后,在硫酸介质中与亚硝酸钠反应,生成环己醇亚硝酸酯,最后用毛细管柱分离,GC-FID检测甜蜜素含量。结果表明,本方法线性范围为0.1～2.0 mg/mL,最低检出限为2 mg/kg,加标回收率为95.4%～113.7%,相对标准偏差为2.34%～4.84%。该方法操作简便、快速、精密度好、准确度高,比较适合用于黄酒中甜蜜素含量的测定。     

分光光度法测定纺织品六价铬的方法验证

为确认实验室使用分光光度法测定纺织品中六价铬含量方法的可靠性和准确性,能达到标准要求,本文按照《纺织品重金属的测定第3部分：六价铬分光光度法》的测试方法测定纺织材料及产品中六价铬的含量。通过对方法的检出限、精密度和准确度的考察,证明实验室有能力使用该方法。结果表明,方法的检出限为0.20mg/kg,精密度≤5%,准确度为96.0%。证明该方法的灵敏度高,重现性好,能满足实验室的检测要求。     

微波消解-石墨炉原子吸收法测定配合饲料中的铅

建立一种微波消解-石墨炉原子吸收光谱仪测定饲料中铅的方法。对石墨炉原子吸收光谱仪条件进行优化,确定了最佳试验条件。在最佳仪器条件下饲料中的铅检出限为0.001 4 mg/kg、回收率为90.0%～105.0%,精密度为4.63%～7.64%。本方法具有灵敏度高、准确度高、精密度好等优点,适用于饲料中铅含量的测定。     

ICP-OES法测定葡萄酒中的矿质元素

利用微波消解仪消化葡萄酒样品,然后用电感耦合等离子体发射光谱法(ICP-OES)快速测定葡萄酒中的矿质元素K、Na、Ca、Mg等的含量,其相对标准偏差为0.2%～4.5%,回收率为88%～105%。此法简便、快速、准确度高、精密度好。     

午餐肉中食盐含量的测定

采用直接沉淀滴定法测定午餐肉中的食盐含量,结果表明,所测样品中食盐含量为1.36g/100g,该方法简单、快速、准确度高,适用于午餐肉中食盐含量的测定。     

离子色谱法测定食盐中的硫酸根

目的建立食盐中硫酸根的离子色谱检测方法。方法利用银柱和钠柱做固相萃取柱,简化样品前处理,对分离硫酸根的淋洗液梯度条件进行了优化设计,建立了食盐中硫酸根含量的自动分析方法。结果在最佳工作条件下,获得硫酸根在1~100 mg/L浓度范围内具有良好的线性关系,加标回收率为97.89~100.50%,相对标准偏差为0.57%。结论方法优化后,基于ICS3000型的离子色谱方法能够去除高浓度氯离子的干扰,缩短样品的处理时间,提高硫酸根的选择性。本方法具有操作简单、响应迅速、干扰小、精确度和灵敏度高等特点。     

Reliable identification of grapevine rootstock varieties using RAPD PCR on woody samples

Since grapevine ( Vitis spp .) rootstock material is being traded increasingly as disbudded woody material a lack of distinctive morphological features on such material necessitates an alternative and reliable means of identification. Methods described here were developed for rapid and efficient extraction of DNA from woody samples rich in phenolic compounds and polysaccharides, and for subsequent identification of varieties by RAPD PCR. Using these methods, and with the application of only one selected RAPD primer, we were able to differentiate sixteen rootstock varieties, including the seven varieties most commonly used in Germany. Problems commonly encountered with reproducibility of RAPD patterns were avoided by choosing primers with a dinucleotide sequence and a high G/C content that allowed a rather high annealing temperature of 45°C. Methods described here should also be useful for other horticultural crops, especially those with woody tissues rich in phenolic compounds and polysaccharides.     

An internet compendium of analytical methods and spectroscopic information for monomers and additives used in food packaging plastics

An internet website (http://cpf.jrc.it/smt/) has been produced as a means of dissemination of methods of analysis and supporting spectroscopic information on monomers and additives used for food contact materials (principally packaging). The site which is aimed primarily at assisting food control laboratories in the European Union contains analytical information on monomers, starting substances and additives used in the manufacture of plastics materials. A searchable index is provided giving PM and CAS numbers for each of 255 substances. For each substance a data sheet gives regulatory information, chemical structures, physico-chemical information and background information on the use of the substance in particular plastics, and the food packaging applications. For monomers and starting substances (155 compounds) the infra-red and mass spectra are provided, and for additives (100 compounds); additionally proton NMR are available for about 50% of the entries. Where analytical methods have been developed for determining these substances as residual amounts in plastics or as trace amounts in food simulants these methods are also on the website. All information is provided in portable document file (PDF) format which means that high quality copies can be readily printed, using freely available Adobe Acrobat Reader software. The website will in future be maintained and up-dated by the European Commission's Joint Research Centre (JRC) as new substances are authorized for use by the European Commission (DG-ENTR formerly DGIII). Where analytical laboratories (food control or other) require reference substances these can be obtained free-ofcharge from a reference collection housed at the JRC and maintained in conjunction with this website compendium.     

Chlorohydrins of bisphenol A diglycidyl ether (BADGE) and of bisphenol F diglycidyl ether (BFDGE) in canned foods and ready-to-drink coffees from the Japanese market

BADGE.2HCl and BFDGE.2HCl were determined in 28 samples of ready-to-drink canned coffee and 18 samples of canned vegetables (10 corn, 5 tomatoes and 3 others), all from the Japanese market. HPLC was used as the principal analytical method and GCMS for confirmation of relevant LC fractions. BADGE.2HCl was found to be present in one canned coffee and five samples of corn, BFDGE.2HCl in four samples of canned tomatoes and in one canned corn. No sample was found which exceeded the 1mg/kg limit of the EU for the BADGE chlorohydrins. However the highest concentration was found for the sum of BFDGE.2HCl and BFDGE.HCl.H₂O at a level of 1.5mg/kg. A Beilstein test confirmed that all cans containing foods contaminated with BADGE.2HCl or BFDGE.2HCl had at lest one part coated with a PVC organosol.     

European priorities for research to support legislation in the area of food contact materials and articles

A strong science base is required to underpin the planning and decision-making process involved in determining future European community legislation on materials and articles in contact with food. Significant progress has been made in the past 5 years in European funded work in this area, with many developments contributing to a much better understanding of the migration process, and better and simpler approaches to food control. In this paper this progress is reviewed against previously identified work-areas (identified in 1994) and conclusions are reached about future requirements for R&D to support legislation on food contact materials and articles over the next 5 or so years.     

Textural Properties of Cold-set Gels Induced from Heat-denatured Whey Protein Isolates

A 9% whey protein (WP) isolate solution at pH 7.0 was heat-denatured at 80°C for 30 min. Size-exclusion HPLC showed that native WP formed soluble aggregates after heat-treatment. Additions of CaCl2 (10–40 mM), NaCl (50–400 mM) or glucono-delta-lactone (GDL, 0.4–2.0%, w/v) or hydrolysis by a protease from Bacillus licheniformis caused gelation of the denatured solution at 45°C. Textural parameters, hardness, adhesiveness, and cohesiveness of the gels so formed changed markedly with concentration of added salts or pH by added GDL. Maximum gel hardness occurred at 200 mM NaCl or pH 4.7. Increasing CaCl2 concentration continuously increased gel hardness. Generally, GDL-induced gels were harder than salt-induced gels, and much harder than the protease-induced gel.     

Aroma characterization of various apricot varieties using headspace–solid phase microextraction combined with gas chromatography–mass spectrometry and gas chromatography–olfactometry

The characterization of the aromatic profile of several apricot cultivars with molecular tracers in order to obtain objective data concerning the aromatic quality of this fruit was undertaken using headspace–solid phase microextraction (HS–SPME). Six apricot cultivars were selected according to their organoleptic characteristics: Iranien, Orangered, Goldrich, Hargrand, Rouge du Roussillon and A4025. The aromatic intensity of these varieties measured by HS–SPME–Olfactometry were defined and classified according to the presence and the intensity of grassy, fruity and apricot like notes. In the six varieties, 23 common volatile compounds were identified by HS–SPME–GC–MS. Finally, 10 compounds, ethyl acetate, hexyl acetate, limonene, β-cyclocitral, γ-decalactone, 6-methyl-5-hepten-2-one, linalool, β-ionone, menthone and (E)-hexen-2-al were recognized by HS–SPME–GC–O as responsible of the aromatic notes involved in apricot aroma and considered as molecular tracers of apricot aromatic quality which could be utilized to discriminate apricot varieties.     

Tests of potential functional barriers for laminated multilayer food packages. Part I: Low molecular weight permeants

The advent of the functional barrier concept in food packaging has brought with it a requirement for fast tests of permeation through potential barrier materials. In such tests it would be convenient for both foodstuffs and materials below the functional barrier (sub-barrier materials) to be represented by standard simulants. By means of inverse gas chromatography, liquid paraffin spiked with appropriate permeants was considered as a potential simulant of sub-barrier materials based on polypropylene (PP) or similar polyolefins. Experiments were performed to characterize the kinetics of the permeation of low molecular weight model permeants (octene, toluene and isopropanol) from liquid paraffin, through a surrogate potential functional barrier (25 μm-thick oriented PP) into the food simulants olive oil and 3% (w/v) acetic acid. These permeation results were interpreted in terms of three permeation kinetic models regarding the solubility of a particular model permeant in the post-barrier medium (i.e. the food simulant). The results obtained justify the development and evaluation of liquid sub-barrier simulants that would allow flexible yet rigorous testing of new laminated multilayer packaging materials.     

Occurrence of bisphenol-F-diglycidyl ether (BFDGE) in fish canned in oil

The levels of bisphenol-F-diglycidyl ether (BFDGE) were quantified as part of a European survey on the migration of residues of epoxy resins into oil from canned fish. The contents of BFDGE in cans, lids and fish collected from all 15 Member States of the European Union and Switzerland were analysed in 382 samples. Cans and lids were separately extracted with acetonitrile. The extraction from fish was carried out with hexane followed by re-extraction with acetonitrile. The analysis was performed by reverse phase HPL C with fluorescence detection. BFDGE could be detected in 12% of the fish, 24% of the cans and 18% of the lids. Only 3% of the fish contained BFDGE in concentrations considerably above 1mg/kg. In addition to the presented data, a comparison was made with the levels of BADGE (bisphenol-A-diglycidyl ether)analysed in the same products in the context of a previous study.     

Contribution of European research to risk analysis

The European Commission's, Quality of Life Research Programme, Key Action 1—Health, Food & Nutrition is mission-oriented and aims, amongst other things, at providing a healthy, safe and high-quality food supply leading to reinforced consumer confidence in the safety of European food. Its objectives also include the enhancing of the competitiveness of the European food supply. Key Action 1 is currently supporting a number of different types of European collaborative projects in the area of risk analysis. The objectives of these projects range from the development and validation of prevention strategies including the reduction of consumers risks; development and validation of new modelling approaches; harmonization of risk assessment principles, methodologies, and terminology; standardization of methods and systems used for the safety evaluation of transgenic food; providing of tools for the evaluation of human viral contamination of shellfish and quality control; new methodologies for assessing the potential of unintended effects of genetically modified (genetically modified) foods; development of a risk assessment model for Cryptosporidium parvum related to the food and water industries; to the development of a communication platform for genetically modified organism, producers, retailers, regulatory authorities and consumer groups to improve safety assessment procedures, risk management strategies and risk communication; development and validation of new methods for safety testing of transgenic food; evaluation of the safety and efficacy of iron supplementation in pregnant women; evaluation of the potential cancer-preventing activity of pro- and pre-biotic ('synbiotic') combinations in human volunteers. An overview of these projects is presented here.