两性聚丙烯酰胺的制备及表征

研究了反相微乳液法聚合制备两性聚丙烯酰胺的影响因素。通过正交实验对两性聚丙烯酰胺反相微乳液聚合的条件进行了优化选择,得出了制备两性聚丙烯酰胺的最佳工艺条件:单体水溶液的pH值为5,反应温度40℃,反应时间4h,引发剂质量百分数为0.4%(相对于水溶液质量),氧化剂与还原剂的质量比为1∶1。在此条件下合成的微乳液体系中各种粒子的平均粒径为73nm,分子量达40万。并用红外光谱(FT-IR)、热失重分析仪(TGA)对两性聚丙烯酰胺共聚物的结构及热稳定性进行了表征。     

DMC/AM/AA反相微乳液体系的制备与优化

以甲基丙烯酰氧乙基三甲基氯化铵(DMC)、丙烯酰胺(AM)和丙烯酸(AA)为乳化单体,采用电导率法和目测法相结合的方式,考察了复合乳化剂的亲水亲油平衡值(HLB)、水相单体浓度和配比、油水质量比等因素对体系电导率和水相增溶量的影响,制备了稳定的DMC/AM/AA反相微乳液体系,优化了反相微乳液体系的制备条件。结果表明,最佳油相为环己烷,最佳乳化体系为Span80-Tween60;HLB为10.48,水溶液中单体总浓度为50%,n(DMC)∶n(AM)∶n(AA)为1.5∶7∶1.5,油水质量比为2∶1时,体系的电导率变化较为平稳,增溶水量也较多,可以得到澄清稳定的反相微乳液体系。     

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。     

壳聚糖接枝丙烯酰胺反相胶乳的合成及应用

采用反相乳液聚合技术对壳聚糖和丙烯酰胺进行接枝聚合反应,结果表明,在油相体积与水相体积比为1:1、壳聚糖与丙烯酰胺质量比为1:8、引发剂(CAN)浓度为0．67 mmol/L、反应时间为4h、乳化及反应温度为50℃、乳化剂用量为7%、m_(Span-80):m_(OP-10)=6:4、搅拌速度为1100 r/min的条件下,可以得到稳定的胶乳,将其用作纸张增强剂取得了较好的应用效果。     

两性聚丙烯酰胺的反相微乳液制备及其在造纸中的应用

在氧化还原引发体系的基础上,采用反相微乳液制备出新型两性聚丙烯酰胺;探讨了各影响因素对两性聚丙烯酰胺相对分子质量和得率的影响,优化了聚合工艺,并针对聚合产品在造纸中的应用进行了初步研究。结果表明,优化后的两性聚丙烯酰胺起到较好的助留助滤作用,同时也可在一定程度上改善成纸的强度性能。     

水包水型有机高分子絮凝剂的合成及絮凝性能

在聚合温度45℃、反应时间为4.5h的反应条件下,采用水分散聚合技术制备出了环境友好型水包水阳离子聚丙烯酰胺稳定乳液,其最优单体配比为:w(PEG20000)=5.5%,w(Al2(SO4)3)=15%,w(AM):w(DMC)=10:3,w(K2S2O8)=O.3%(单体).并将所得聚合产物用于高岭士絮凝实验以及将其与聚合氟化铝复合用于造纸废水的絮凝实验,并测定其上清液的透光率和CODcr,得出CPAM的最佳用量.     

CPAM特性黏数影响因素研究

采用反相乳液聚合法合成了CPAM,确定最佳工艺条件为∶V（油相）∶V（水相）=1.20∶1,反应温度35℃,水相pH=5.5,w（DMC）∶w（AM）=2.1∶1,w（乳化剂）=8.4%,w（单体）=35.4%,引发剂占水相的0.23%.在此条件下,聚合物特性黏数可达6.97 dL.g^-1.     

核壳型酮肼自交联苯丙微皂乳液表面施胶剂的合成

采用半连续种子乳液聚合工艺合成了具有核壳结构的酮肼自交联苯乙烯—丙烯酸酯微皂乳液新型表面施胶剂。加入功能性单体双丙酮丙烯酰胺(DAAM)、己二酰肼(ADH)和丙烯酰胺(AM),选用乳化能力较强的非离子乳化剂OP-10和反应型的阴离子乳化剂A-2405的复合乳化剂体系,并对乳液聚合的工艺参数进行了实验研究,得到最佳反应条件为硬软单体比例3∶7,反应温度70℃,反应时间共7h,乳化剂用量6%,功能性单体用量3%,交联pH值为9。在此条件下可制得稳定、转化率高达99%的苯丙乳液。用作表面施胶剂,涂布后的纸页不仅具有优良的抗水性能,而且具有较高的光泽度。     

反相微乳液制备两性聚丙烯酰胺的工艺优化

通过电导率和透光率来优化反相微乳液制备两性聚丙烯酰胺的合成工艺,得到最佳合成条件为:EDTA加入量0.5%(对单体质量)、搅拌速度为300 r/min、乳化剂用量为18.61%(对乳液总质量)、反应时间为3 h、引发剂用量为0.5%(对单体质量)、单体质量分数为50%(对水相质量)、反应温度为25℃;并检测了在此优化条件下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。     

椰子油微乳的制备及其性质研究

用非离子型表面活性剂司班80和吐温80制备椰子油微乳,考察制备方法、亲水亲油平衡值(hydrophilic lipophilic balance value,HLB)、助乳化剂和乳化剂用量对微乳形成的影响,以确定椰子油微乳的最优制备工艺参数。结果表明,复合乳化剂的HLB值为12,助乳化剂为丙三醇,乳化剂用量为油水总量的3.2%时,用超声辅助搅拌的方法能制备稳定的o/w型椰子油微乳。当椰子油和乳化剂与水的质量比为1∶9和2∶8时制得的微乳稳定性最佳,而3∶7时制得的微乳在低温下不太稳定。     

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.     

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.     

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.     

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.     

Analysis of benzo[a]pyrene in spiked fatty foods by second derivative synchronous spectrofluorimetry after microwave-assisted treatment of samples

A simple, rapid and inexpensive method has been developed for the determination of benzo[a     

The development of reference materials for paralytic shellfish poisoning toxins in lyophilized mussel. II: Certification study

This paper describes the second part of a project undertaken to develop certified mussel reference materials for paralytic shellfish poisoning toxins. In the first part two interlaboratory studies were undertaken to investigate the performance of the analytical methodology for several PSP toxins, in particular saxitoxin and decarbamoyl-saxitoxin in lyophilized mussels, and to set criteria for the acceptance of results to be applied during the certification exercise. Fifteen laboratories participated in this certification study and were asked to measure saxitoxin and decarbamoyl-saxitoxin in rehydrated lyophilized mussel material and in a saxitoxin-enriched mussel material. The participants were allowed to use a method of their choice but with an extraction procedure to be strictly followed. The study included extra experiments to verify the detection limits for both saxitoxin and decarbamoyl-saxitoxin. Most participants (13 of 15) were able to meet all the criteria set for the certification study. Results for saxitoxin.2HCl yielded a certified mass fraction of <0.07 mg/kg in the rehydrated lyophilized mussels. Results obtained for decarbamoyl-saxitoxin.2HCl yielded a certified mass fraction of 1.59+/-0.20 mg/kg. The results for saxitoxin.2HCl in enriched blank mussel yielded a certified mass fraction of 0.48 +/- 0.06 mg/kg. These certified reference materials for paralytic shellfish poisoning toxins in lyophilized mussel material are the first available for laboratories to test their method for accuracy and performance.     

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.