羧乙基微纤化纤维素/石墨烯/聚苯胺复合膜的制备与表征

以羧乙基微纤化纤维素为基体,分别采用物理混合法、化学原位吸附聚合法以及物理共混与化学原位吸附聚合相结合的方法经棒涂成型制备了羧乙基微纤化纤维素/石墨烯复合膜、羧乙基微纤化纤维素/聚苯胺复合膜和羧乙基微纤化纤维素/石墨烯/聚苯胺复合膜,对复合膜的微观形貌、化学结构、耐水性、热稳定性、力学性能和电化学性能进行了表征。结果表明,羧乙基微纤化纤维素具有良好的成膜性,可起载体和分散剂的作用。复合石墨烯或聚苯胺后,复合膜的力学性能和电化学性能明显增加。石墨烯可提高膜的热稳定性,聚苯胺可增加膜的耐水性。另外,当10%的石墨烯和30%的聚苯胺复合时,还会对羧乙基微纤化纤维素/石墨烯/聚苯胺复合膜的电化学性能产生协同增效的作用。     

不同纤维原料对羧乙基微纤化纤维素膜性能的影响

采用6种不同的纤维原料（漂白硫酸盐阔叶木浆、漂白硫酸盐竹浆、漂白硫酸盐针叶木浆、棉短绒浆、漂白针叶木化学机械浆和玉米芯纤维素）经羧乙基化预处理和机械研磨制备了微纤化纤维素（Microfibrillarized cellulose,MFC）,并通过涂布法制备了MFC膜。探讨了原料羧基含量、研磨程度和原料种类对MFC及其膜性能的影响。结果表明,随着预处理后漂白硫酸盐阔叶木浆羧基含量的增加,MFC的保水值由98%增加到538%,MFC膜的孔隙率由37%下降至19%。当羧基含量为0.8 mmol/g时,MFC膜的抗张强度最高,达53 MPa。另外,随着研磨程度（次数）的增加,所得MFC纤丝化程度提高,MFC膜的强度先升高后降低,最高值为75 MPa。在最优的羧乙基化预处理条件和研磨程度下,由6种不同纤维原料制备的MFC膜中,漂白硫酸盐竹浆所得MFC膜的强度最高,为84 MPa,其孔隙率为25%。     

氨基甲酰乙基微纤化纤维素的制备及改性

采用氨基甲酰乙基化反应对阔叶浆进行预处理,再经机械研磨得到了微纤化纤维素,最后分别在酸性和碱性条件下用次氯酸钠对其进行了改性。探讨了预处理条件对产物中氨基甲酰乙基和羧乙基含量的影响,并对预处理产物、微纤化纤维素和次氯酸钠改性产物的结构和热稳定性进行了表征。结果表明,预处理过程中丙烯酰胺和氢氧化钠用量以及反应温度会影响产物中氨基甲酰乙基和羧乙基的含量,经研磨后可得到直径为亚微米级的氨基甲酰乙基微纤化纤维素,再经次氯酸钠改性后可得到N-氯氨甲酰化纤维素产品,改性后纤维素产品的初始分解温度和最大失重温度均明显降低,但其残留率显著增加。     

羧乙基化法制备纳米纤化纤维素

以阔叶木为原料,采用丙烯酰胺与氢氧化钠溶液对纤维素进行羧乙基化处理,引入羧乙基基团,然后在高压均质的条件下制备纳米纤化纤维素。研究丙烯酰胺用量、氢氧化钠用量、反应温度和反应时间对羧乙基含量的影响。单因素实验最优制备条件为丙烯酰胺用量1.89 g·g^-1绝干浆,氢氧化钠用量1.51 g·g^-1绝干浆,反应温度90℃,反应时间5h;对不同羧乙基含量的纳米纤化纤维素的性能进行表征,包括:长度、直径、长径比、聚合度和透过率。结果表明:羧乙基含量越高,尺寸和聚合度越小,透过率越高。当羧乙基含量1.89 mmol·g^-1时,纳米纤化纤维素的直径为20nm左右,长度为1.5μm左右,长径比为80左右,在800 nm处透过率为83.89%,聚合度为265。     

纳米甘薯渣纤维素的添加对玉米淀粉可食性膜性能的影响

以水蒸气透过性、吸湿性、溶解性、抗拉强度和断裂伸长率为指标,研究纳米甘薯渣纤维素对玉米淀粉可食性膜性能的影响。结果表明:随着添加的纳米甘薯渣纤维素质量浓度的增大,玉米淀粉可食性膜的水蒸气透过性、吸湿性、溶解性和断裂伸长率逐渐减小,而抗拉强度逐渐增大。当纳米甘薯渣纤维素的质量浓度为0.4g/100mL时,膜的水蒸气透过率最小;当纳米甘薯渣纤维素的质量浓度为0.5g/100mL时,膜的吸湿性、溶解性和断裂伸长率最小,而抗拉强度最大。提示纳米甘薯渣纤维素的添加能有效改善膜的性能。     

羧甲基化改性纳米甘薯渣纤维素的表征

以甘薯渣为原料,利用超声辅助酸法从薯渣中提取纳米纤维素,用羧甲基化对纳米纤维素进行亲水性改性,并对其理化性质进行表征。结果表明,羧甲基纳米纤维素仍为典型的球形粒子,粒径集中分布在30~50nm,与原纳米纤维素相比,表面结构更加疏松,化学反应活性增强;改性纳米纤维素的晶型结构发生了变化,结晶度明显降低,结晶指数由原来的73.27%下降到52.83%,但其热稳定性提高;改性纳米纤维素的实测纯度99.5%,黏度25 mPa·s,是一种高纯度极低黏度的纳米级羧甲基纤维素,可用做食品级添加剂。     

纤维素纳米化处理技术研究现状

纳米纤维素因具有可再生、易改性以及优异的机械性能,在众多领域具有广阔的应用前景。植物来源的纳米纤维素主要包括纤维素纳米晶体和纤维素纳米纤维,本文主要介绍了以农副产品为原料的纤维素纳米化处理技术及其分类,包括制备纤维素纳米晶体的经典无机酸水解法以及有机酸水解法、低共熔溶剂法和离子液体法等新型制备方法。此外,还介绍了制备纤维素纳米纤维常用的预处理手段和制备方法,预处理方法包括以2,2,6,6-四甲基哌啶-1-氧自由基氧化为代表的氧化法预处理以及酶法预处理;制备方法包括高压均质、精细研磨、高强度超声和高压微射流等技术。最后,对现行纤维素纳米化处理技术中存在的问题进行综合分析,并探讨了其未来研究需求,以期为纳米纤维素的绿色高效生产提供理论参考。     

基于NaOH-Urea预处理的微纤化纤维素制备研究

为开发高效制备微纤化纤维素的方法,探讨了基于氢氧化钠-尿素（NaOH-Urea）混合溶液对玉米芯微晶纤维素进行预处理后采用机械法处理的微纤化纤维素制备工艺。采用傅里叶变换红外光谱仪（FT-IR）、X射线衍射仪（XRD）、热重分析仪（TG）、场发射扫描电镜（FESEM）对制备的微纤化纤维素化学结构、结晶度、热稳定性及微观形貌进行表征。结果表明,制备的微纤化纤维素为纤维素Ⅰ型;微纤化纤维素的结晶度为604%,得率高达78%;微纤化纤维素结晶度较玉米芯微晶纤维素有所提高;制备的微纤化纤维素表现出优良的热稳定性,热降解温度达238℃;微纤化纤维素呈棒状,直径为5～20 nm,长度大于200 nm。     

超声波辅助酸法制备纳米薯渣纤维素的工艺研究

为了提高甘薯加工副产品的高值化利用,以甘薯渣纤维素为原料,应用超声波辅助酸法制备纳米薯渣纤维素。通过对超声波功率、酸体积分数、酸解温度和酸解时间4个影响因素进行单因素及正交试验,获得了纳米薯渣纤维素的最佳制备条件,并通过透射电镜和X-射线衍射对其进行进一步的分析。结果表明:纳米薯渣纤维素制备的最佳工艺参数为超声波功率120 W、酸体积分数65%、酸解温度55℃、酸解时间120 min,此条件下纳米薯渣纤维素的产率为42.85%;纳米薯渣纤维素的形态表现为不规则球状,粒径在20～40 nm范围内,并且其仍具有纤维素的晶型,结晶度有明显的提高。     

负载纳米氧化锌的明胶/乙基纤维素气凝胶的制备及抑菌能力分析

本实验旨在构建一种明胶/乙基纤维素气凝胶,研究其三维结构与物理性能,并装载纳米氧化锌测试其抑菌能力.通过静电纺丝技术制备明胶/乙基纤维素纳米纤维膜,再将该膜通过冷冻干燥方法制备成气凝胶,并添加海藻酸钠和氯化钙进行交联;通过测定微观形貌、孔隙率、热导率、水稳定性、机械性能、热稳定性和晶体形态等对气凝胶的理化性质进行分析,...     

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.     

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.     

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.     

Announcing a new international peer-reviewed journal:Food Science and Human Wellness now accepting manuscript submission in English

<正>We are pleased to announce the launch of a new international peer-reviewed journal-Food Science and Human Wellness,ISSN 2213-4530,which is an open access journal,produced and hosted by Elsevier B.V.on behalf of Beijing Academy of Food Sciences.Food Science and Human Wellness is an international peer-reviewed English journal that provides a forum for the dissemination of the