紫外分光光度法测定食盐中微量碘

抗坏血酸溶液在紫外有最大吸收峰,在稀盐酸介质中,微量的碘酸钾能氧化抗坏血酸溶液而使吸光度降低,降低程度与碘酸钾浓度成正比,从而建立了紫外分光光度法测定碘含量的新方法。方法是体系反应后于最大吸收波长243nm处测量吸光度。碘酸钾浓度在0.1~4.0μg/mL范围内呈良好的线性关系,相关系数为0.9981,摩尔吸光系数2.3×104 L/mol·cm。用此法测定食盐中微量碘含量,RSD最大值4.20%(n=5),加标回收率在90.2%~107.0%之间。     

铬蓝黑R褪色光度法测定食盐中碘含量

研究了在酸性介质中,碘酸根氧化铬蓝黑R的褪色反应。实验结果表明,碘酸钾-铬蓝黑R-硫酸反应体系的最大吸收波长为518nm,碘浓度在0-1.2mg/L范围内遵守朗伯-比尔定律,ΔA与浓度之间呈线性关系;518nm条件下该反应的相关系数为0.9992,表观摩尔吸光系数为2.538×104L.moL-1.cm-1。用于测定食盐中微量的碘,相对标准偏差为0.24%-0.28%,回收率为99.1%-102.7%,此方法准确度较高,操作简便、快捷,是测定加碘食盐中碘含量的较好方法之一。     

食盐加碘剂碘酸钾的测定研究

在硫酸介质中,碘酸钾与桑葚红反应褪色程度与碘酸根量在一定范围内呈线性关系,从而建立了碘的光度测定新方法.结果表明,方法的最大吸收波长在520 nm处,碘定量测定的线性范围为0～50 mg/25 mL,摩尔吸光系数ε=4.3×104 L/mol· cm.研究可直接测定食盐中的碘,结果满意.     

淀粉作显色剂分光光度法测食盐中碘酸钾含量的研究

淀粉遇碘显色灵敏,稳定,建立了测定食盐中微量碘酸钾含量的新方法。方法的摩尔吸光系数为=2.210L/ (mol.cm),最大吸收波长是580nm, 检出限为2靏/ml,线性范围2～15靏/ml。本方法经济、简单、快速、准确、无污染.     

结晶紫-亚砷酸钠体系光度法测定食盐中的碘

在盐酸介质中,过量的亚砷酸钠还原碘酸根离子释放出I3-,其与结晶紫发生氧化还原反应,且反应前后吸光度的差值与碘酸根的浓度成正比,建立了紫外分光光度法测定微量碘的新方法.碘酸钾含量在6 mg/L～20 mg/L范围内服从朗伯-比耳定律,线性方程为Y=0.045 7 0.484 7X,相关系数r=0.995 8,检出限为0.068 6 mg/L(以K103计).用该方法测定了食盐的碘含量,回收率在96.0%～101.0%之间.     

线性扫描伏安法测定食盐中碘含量

以多壁碳纳米管(MWCNT)修饰玻碳电极为工作电极,研究了碘离子在该修饰电极上的伏安分析特性,建立了测定食盐中碘含量的线性扫描伏安法。在优化实验条件下,氧化峰电流与碘离子浓度在1.0×10-6～1.0×10-3 mol/L范围内呈良好的线性关系,检出限为4.0×10-7 mol/L。对1.0×10-4 mol/L碘化钾溶液平行测定10次的RSD为3.2%。将该方法用于测定加碘食盐中的碘含量,结果满意。     

山梨酸氧化紫外光度法测定食盐中碘酸钾

山梨酸溶液在紫外光谱下具有最大吸收峰,在盐酸介质中,在溴化钾的催化作用下,碘酸钾能氧化山梨酸而使吸收峰降低,降低程度与碘酸钾含量成正比,从而建立了测定碘酸钾含量的新方法。碘酸钾氧化山梨酸后,用乙酸铵缓冲溶液控制溶液的pH值为7,溶液体系的最大吸收波长λmax为254nm,碘酸钾浓度在0~3.6μg/mL范围内与吸光度呈良好的线性关系,线性回归方程为:△A=0.1827C+0.0144,相关系数为0.9986,摩尔吸光系数为4.0×104 L/mol·cm。方法用于测定加碘食盐中碘酸钾含量,相对标准偏差(n=6)为3.14%,加标回收率(n=6)为94.0%~103.0%。     

亚甲基蓝氧化褪色光度法测定食盐中的碘

在盐酸介质中,碘酸根在加热的条件下能氧化亚甲基蓝褪色,建立了亚甲基蓝氧化褪色法测定微量碘的新方法.讨论了实验条件,最大吸收峰为667 nm,碘酸钾浓度在01.2 μg/mL范围内呈线性关系,摩尔吸光系数为1.1×105 L·mol-1·cm-1.用于测定食盐中微量碘的含量,结果满意.     

靛蓝胭脂红氧化褪色光度法测定食品中微量碘

基于稀硫酸介质中,在溴化钾的催化下,碘酸根对靛蓝胭脂红有明显的褪色作用,且褪色的程度与碘酸根的含量有关,建立氧化褪色光度法测定微量碘的方法.碘定量测定的线性范围为20 μg/25 mL～50 μg/25mL,方法的检出限为1.25×10-1 μg/mL,反应的表观摩尔吸光系数为1.354 L/(cm·mol).本法的灵敏度和选择性较高,重现性好,操作简便,用于测定海带或食盐等含微量碘较高的食品,结果满意.     

表面活性剂增敏光度法测定食盐中的碘

建立了碘酸根-荧光黄-表面活性剂体系下测定食盐中碘的方法。采用增敏光度法研究在醋酸介质中,表面活性剂存在下,溴化钾催化KIO3氧化荧光黄的褪色反应。结果表明：最大吸收波长为438.5 nm,KIO3质量浓度在0.40～3.00 μg/mL范围内遵守朗伯-比尔定律,ΔA与KIO3质量浓度之间呈线性关系;438.5 nm波长条件下该反应的相关系数为0.999 0,表观摩尔吸光系数为4.31×104 L/（mol·cm）。用于测定食盐中微量的碘,相对标准偏差为0.83%～1.47%,回收率为98.1%～98.4%,此方法准确度较高,操作简便、快捷,是测定加碘食盐中碘含量较好的方法之一。     

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.     

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.     

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.     

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.