新型两性聚丙烯酰胺对二次纤维的助留助滤性能

采用反相微乳液聚合制备了新型的两性聚丙烯酰胺助留助滤剂，通过检测两性聚丙烯酰胺对二次纤维的助留助滤性能优化聚合工艺，得到最佳聚合条件为：EDTA加入量0．5％（对单体质量）；搅拌速度为300r／min；乳化剂用量为18．61％（对乳液总质量）；反应时间为3h；引发剂用量为0．5％；单体质量分数为50％（对水相质量）；反应温度为25℃。检测了优化后制备的两性聚丙烯酰胺的助留助滤性能，结果表明，该两性聚丙烯酰胺具有较好的助留助滤性能，当加入量为0．08％（对绝干浆）时，纸料留着率提高了8．9％，打浆度降低了6．1°SR。     

季铵型两性聚丙烯酰胺的合成及应用

采用反相微乳液法合成了季铵型两性聚丙烯酰胺,检测了制备的两性聚丙烯酰胺的助留助滤及增强性能。实验结果表明,当加入量为0.5%时,纸张的抗张指数提高了11.37%,撕裂指数提高了18.52%,填料留着率提高了7.66%,打浆度下降了12.9%,此时助留、助滤及增强效果最好。     

反相微乳液制备两性聚丙烯酰胺的正交实验优化

通过正交实验分别探讨了反应温度、引发剂用量、反应时间和单体浓度对两性聚丙烯酰胺(PDAA)的相对分子质量、转化率和乳液稳定性及其对纸料的助留助滤性能的影响。通过比较产品质量和对纸料的助留助滤性能,得到了制备PDAA的最佳条件为:EDTA加入量为0.5%(基于单体质量)、充氮时间为20 min、搅拌速度为300 r/min、乳化剂用量为18%(基于单体质量)、引发剂用量为0.4%(基于单体质量)、单体浓度为54%(基于水相)、反应温度为24℃和反应时间为3 h。并采用红外光谱和紫外光谱对PDAA结构进行了表征,结果说明,通过反相微乳液制备PDAA获得成功。     

新型CPAM的合成及CPAM／膨润土体系的助留助滤性能

以自制阳离子单体、丙烯酰胺为聚合单体,采用共聚法合成出新型阳离子聚丙烯酰胺(CPAM)。采用正交实验对合成影响因素和CPAM/膨润土微粒助留系统的助留助滤性能进行了探讨。实验结果表明,当引发剂质量分数为0.05%,n(丙烯酰胺)∶n(阳离子单体)=8∶1、反应温度55℃时,CPAM/膨润土具有较好的助留助滤效果。     

阳离子聚丙烯酰胺水包水乳液的分散聚合及其应用

以丙烯酰胺(AM)和丙烯酰氧乙基三甲基氯化铵(DAC)为共聚单体,采用分散聚合法在无机盐水溶液中制备了性能稳定的阳离子聚丙烯酰胺(CPAM)水包水乳液.研究了单体配比、引发剂用量、聚合浓度、分散剂用量等因素对聚合反应的影响.动态滤水实验表明,自制CPAM对漂白苇浆具有良好的助留助滤作用.     

交联型阳离子聚丙烯酰胺乳液的合成与应用

水基分散体交联型阳离子聚丙烯酰胺(CPAM)是一种新型的阳离子助留助滤剂,具有抗高剪切力和抗盐作用。本实验采用分散聚合法合成了一种固含量为15%的交联型CPAM乳液,研究了其合成的最佳工艺条件,并将自制交联型CPAM与市售直链型CPAM进行比较。结果表明,当总单体质量分数为15%,甲基丙烯酰氧乙基二甲基氯化铵(DMC)与丙烯酰胺(AM)的摩尔比为0.15,引发剂用量为单体总质量的0.11%,N,N'-亚甲基双丙烯酰胺(MBA)用量为40 mg/kg,甲基烯丙基磺酸钠(SMAS)用量为600 mg/kg,反应温度为56℃时,所合成产品的性能最优。在高剪切力与高电导率条件下,自制交联型CPAM的助留助滤性能优于市售直链型CPAM乳液的。     

阳离子聚丙烯酰胺的Hofmann法制备及其助留助滤性能

采用水溶液自由基聚合制备了非离子型聚丙烯酰胺,再经过Hofmann降解法得到阳离子聚丙烯酰胺。然后用正交实验对Hydrocol体系的助留助滤性能进行了研究,实验表明,Hydrocol体系最佳配方为阳离子聚丙烯酰胺的加入量为0.08%、分子量为403万,膨润土用量为0.4%,灰分量最大可提高0.79%,打浆度最大可降低5.13SR,表明由自制阳离子聚丙烯酰胺与膨润土构成的Hydrocol体系具有较理想的助留助滤性能。     

阳离子聚丙烯酰胺/膨润土体系的助留助滤性能

采用水溶液自由基聚合制备了非离子型聚丙烯酰胺,再经过Hofmann降解法得到阳离子聚丙烯酰胺。然后用正交实验对Hydrocol体系的助留助滤性能进行了研究。实验表明,Hydrocol体系最佳配方为阳离子聚丙烯酰胺的加入量0.08%、分子量403万,膨润土用量0.4%,灰分含量最大可提高0.79%,打浆度最大可降低5.13°SR,表明自制阳离子聚丙烯酰胺与膨润土构成的Hydrocol体系具有较理想的助留助滤性能。     

AM—DMC乳液的合成及在造纸中的助留助滤作用

以丙烯酰胺(AM)、甲基丙烯酸二甲氨基乙酯氯甲烷盐(DMC)、聚醚分散剂等为原料,采用乳液聚合法,合成出了一系列AM-DMC阳离子共聚物乳液,测定了乳液的粘度与稳定性,找出了合成AM-DMC阳离子共聚乳液的最优配方和条件.把AM-DMC阳离子共聚乳液加到废纸浆中,测其打浆度与留着量等,当AM-DMC乳液用量为0.10%时,其助留助滤效果最好.     

两性高分子聚丙烯酰胺助留助滤剂在非木材纤维中的应用效果

在非木材草类纤维中加入两性高分子聚丙烯酰胺助留、助滤剂，对其效果进行了探索。实验结果表明：用量在1％时，其助滤、助留的效果最好。但高分子的聚丙烯酰胺的助滤效果远不及助留效果好。     

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.