螯合处理过氧化氢漂白中的金属离子

一些过渡金属离子如Mn2 、Cu2 、Fe2 等能加速过氧化氢（H2O2）分解，影响H2O2的稳定性。在H2O2漂白前，添加蛰合剂可去除过渡金属离子，建立最佳金属离子多数。1全局离子对碱性H刃；分解的影响碱性H刀。金属催化分解七。下：H刃。＋M（金属）～HO”＋HO＋M”（1）H几十HO’～HO。”＋H刀（2）H02”＋M＋～O：＋H＋＋M（3）H02”＋H刃～OtopH刃十（4）不同金属高于对H刀。分解影响不同。表1列出了碱性H刀2在金属离子和稳定剂存在下的分解速率常数。表1添加过渡全属离子和稳定剂Kn。从路发空省份问uP】碱性H刀。分解与Mn‘”…     

机械浆H2O2漂白中MgSO4、DTPA和Na2SiO3的作用

从防止H2O2分解角度对MgSO4、DTPA和Na2SiO3的适宜用量进行了探讨,对3种漂白助剂在机械浆H2O2漂白中的作用进行了比较,同时对DTPA预处理对H2O2漂白的效果进行了评价。在含有过渡金属离子的碱性H2O2溶液中,3种助剂适宜用量分别为：MgSO4为0．05％～0.1％．DTPA为0.1％-0．5％,Na2SiO3为0.5％～3．0％。Na2SiO3的使用效果明显好于DTPA。两段H2O2漂白的正交实验表明,在影响机械浆H2O2漂白的3种助剂中,Na2SiO3是最显著的影响因素,其次是DTPA。对机械浆进行DTPA预处理可以改善H2O2漂白效果,增加残余H2O2和降低浆料的返黄值.DTPA预处理的适宜用量为0．3％～0.5％．     

金属离子对萝卜红色素稳定性影响

研究了几种常见金属离子Na＋、Ca2＋、Mg2＋、Fe3＋、Cu2＋、Zn2＋、Sn2＋、Al3＋、Mn2＋等对萝卜红色素的稳定性的影响。     

重金属离子在碱性H2O2溶液中的存在形态及其对H2O2的催化分解作用

Fe2 、Fe3 、Cu2 、Mn2 离子在碱性H2O2漂白体系中随pH值的变化会改变存在形态,对H2O2的催化活性也会随着形态的改变而有所不同。文章主要介绍了这4种重金属离子在不同pH值条件下的不同形态及其对H2O2的分解催化活性和最佳稳定剂的使用。     

硫酸盐蓝桉浆ECF漂白中H_2O_2末段漂与漂白工艺及纤维素降解的关系

以DED和OQPOD漂后浆为对象,进行H2O2终漂性能的优化研究。结果表明,从DED浆的可漂性、漂白选择性及返黄性方面考虑,在P末段漂中,添加DTPA是最有效的提高上述性能的方法。对于OQPOD浆,同时添加DTPA和镁离子时,所得浆料的漂白效果最好。根据P末段漂的前各段漂对金属离子含量的影响,研究了添加不同配比的螯合剂（EDTA或DTPA）和镁离子对浆料的可漂性、漂白选择性及返黄性的影响,从而确定出最优的H2O2稳定剂。在H2O2漂白段中,浆料中Mg/（Fe＋Cu）的比值可作为重要的工艺参数用来控制纤维素的降解。     

在废纸脱墨的FAS漂白段加入Na2SiO3和螯合剂

甲脒亚磺酸（FAS）是一种还原性漂白剂,它可以去除废纸浆中的染料,其漂白效果比连二亚硫酸钠好。当用Na2SiO3代替NaOH控制FAS漂白段的pH值时,漂白效果更好。Na2SiO3可以减少过渡金属离子（包括Mn^2＋和铁离子）的影响。在FAS漂白段同时加入螯合剂和Na2SiO3,FAS漂白后再进行H2O2漂白,最终纸浆折度比不加这2种物质纸浆的白度高。由于一些过渡金属离子和颜料已经在FAS段被去除,使H2O2消耗量较少,改善了后续H2O2的漂白效果。     

金属离子对酶活性影响研究

研究了不同金属离子对β-葡聚糖酶及木聚糖酶酶活力的影响.结果表明:Na+、K+、Mg2+、Mn2+、Fe3+、Ca2+对β-葡聚糖酶具有激活作用,而Cu2+对其起抑制作用,Na+、K+、Ca2+对木聚糖酶具有激活作用,Mg2+、Mn2+、Fe3+,、Ca2+则对其起抑制作用.     

金属离子对常用四种食用合成色素稳定性的影响

研究了几种金属离子对常用四种食用合成色素(胭脂红、赤藓红、柠檬黄和亮蓝)的稳定性的影响,以及EDTA-2Na对色素的护色作用。实验结果表明,Mg2 对胭脂红和赤藓红有明显的增色效果;Cu2 会使胭脂红和柠檬黄溶液分别发生变色和褪色现象;Fe3 可以和胭脂红、亮蓝和柠檬黄结合形成不溶物;EDTA-2Na能够螯合Cu2 和Fe3 形成稳定的络合物,从而有效地抑制了Cu2 和Fe3 对色素稳定性产生的不良影响。     

猪苓色素的提取工艺及稳定性研究

通过正交试验确定猪苓色素提取的最佳工艺条件,研究色素的溶解性、热稳定性、光稳定性以及氧化剂、pH值与金属离子对色素的影响。结果表明,料液比1:60时,以1mol/LNaOH溶液为提取剂、提取温度95℃、时间90min是猪苓色素的最佳提取工艺;干燥的猪苓色素为深褐色粉末,能溶于水,易溶于碱性溶液,热稳定性好,光照会加速其分解,对H2O2不稳定,溶液pH值5～10范围时色素表现稳定;Na+、K+、Ca2+、Mg2+、Zn2+等离子不影响色素的稳定性,而Mn2+、Fe2+、Fe3+及Cu2+则有影响,其中Fe3+和Cu2+影响尤为明显。     

不同金属离子对多酚氧化酶的影响

采用匀浆法从茄子中提取多酚氧化酶(PPO),以绿茶粉为底物,研究Cu2+、Mn2+、Mg2+、Ca2+、Na+、Al3+和Fe3+7种金属离子对PPO活性的影响。结果表明:Cu2+、Mn2+和Mg2+3种金属离子对PPO的活性有不同程度的促进作用,而Ca2+、Na+、Al3+和Fe3+对PPO的活性有抑制作用。其中,Cu2+浓度为3mmol/L时对PPO有激活作用,此时茶黄素总量达到7.45mg;Fe3+浓度为5mmol/L对PPO有显著抑制作用,此时茶黄素总量降低至0.26mg。     

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.     

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.     

低温带皮菜籽粕微粉的不同粒级部分的功能特性

为研究低温带皮菜籽粕微粉的不同粒级部分的功能特性,以经低温脱脂的带皮菜籽粕为原料,经微粉碎后筛分成212~425μm、150~212μm和106~150μm的3个不同粒级的微粉样品,检测这些样品的吸水性、吸油性、乳化性和乳化稳定性、蛋白质体外消化率。结果表明:1 3个不同粒级的微粉样品之间的粗纤维含量存在显著差异,表明三者的结构组成成分有一定差异。23个微粉样品的乳化活性和乳化稳定性随粒度级别的减小而显著增加(P0.01)。33个微粉样品的蛋白质体外消化率随粒度级别的减小而显著增加(P0.01)。4不同粒级带皮菜籽粕微粉样品的吸水性与吸油性受其结构组成物质不同和粒度的双重影响,与粒度的相关性不明显。     

Microbiology of food taints

Fresh and processed foods are often spoilt by the presence of undesirable flavours and odours caused by microbial action. The aim of this paper is to review the current knowledge of microbiologically induced taints that occur in a wide range of foodstuffs, including meats, poultry, fish, crustaceans, milk, dairy products, fruits, vegetables, cereals and cereal products. Examples have been chosen where the compounds responsible for the taint have been identified and sufficient data obtained to demonstrate the involvement of microorganisms. However, in some cases the full identity of the causative organism may not have been elucidated. The types of microorganisms covered by this review include bacteria, fungi, yeasts, actinomycetes and cyanobacteria. Although cyanobacteria do not in general infect foods, their presence in aqueous systems and water supplies can lead to off-flavours in aquatic organisms and processed foodstuffs. Several examples of each of these processes are discussed. Wherever possible, the likely biosynthetic pathway used by the microorganism to produce the offending compound in a foodstuff is indicated.