升温速率对卷烟烟丝快速热解的影响

为考察升温速率对卷烟烟丝快速热解行为的影响,采用热重-质谱联用技术对卷烟烟丝在不同升温速率(200 K·min~(-1)~800 K·min~(-1))下的热解特性进行研究,并建立了不同升温速率下卷烟烟丝的快速热解动力学模型。结果表明:(1)随着升温速率的升高,烟丝各主要成分热分解温度区间的叠加程度、热解速率以及释放特性指数均呈递增趋势,且有不同程度的热滞后现象。(2)引入升温速率校正因子的动力学模型能够克服热滞后所引起的动力学参数偏差,可以更好地预测不同升温速率下卷烟烟丝的快速热解行为。(3)高升温速率下,热解烟气产物中质荷比(m/z)为56(丙烯醛)、79(吡啶)、84(烟碱)、94(苯酚)和117(吲哚)的化合物释放量减小。在高升温速率下卷烟烟丝的快速热解特性与卷烟燃烧的真实状态更为接近,建立的卷烟燃烧数学模型更加准确。     

烟粉和烟丝的热解燃烧特性及反应动力学分析

为了解尺寸对烟草原料热解燃烧动力学特性的影响,利用宏量型烟草高温热转化热重分析仪分析了不同切丝宽度烟丝及其粉碎后烟粉的热解燃烧特性,并使用Coats-Redfern法计算了样品在热解或燃烧过程中各失重阶段的动力学参数。结果表明:①烟粉的最大热解失重速率显著高于烟丝,而0.8～1.2mm范围内3种不同切丝宽度对烟丝的热解失重速率影响不明显;②烟粉在燃烧过程中,生物质三组分热转化导致的挥发分析出与燃烧反应失重峰在DTG曲线中合并为1个失重峰,而烟丝在该热转化过程表现为3个独立的失重阶段;③烟粉的起燃温度Ti高于烟丝、燃尽温度Tb显著低于烟丝,其综合燃烧特性指数S为4.75×10~(-7)%2·min~(-2)·℃~(-3),而3种切丝宽度烟丝的S值在2.63×10~(-7)～2.99×10~(-7)%2·min~(-2)·℃~(-3)范围内变化,且切丝宽度越小综合燃烧特性指数越高;④Coats-Redfern法热解动力学结果显示,在Zone 2对应的小分子有机物热解温度范围内,烟粉的热解动力学主要由2级化学反应控制,而烟丝主要受三维扩散控制。烤烟尺寸越小其燃烧性越好,且与烟粉相比,烟丝在热转化过程中受到更加显著的传热传质阻力的影响。     

基于分布活化能模型的烟草燃烧动力学特性研究

为研究烤烟烟叶的燃烧反应动力学特性,选取烤烟烟叶进行热重实验,考察了烟叶部位、氧气浓度和升温速率对烟叶燃烧过程的影响,利用分布活化能模型(DAEM)获得了中部烟叶燃烧动力学参数。结果表明:1在0~10%的O_2浓度范围内,氧气浓度提高对挥发分的析出过程影响较小,但可显著改善烟草半焦燃烧过程。2提高升温速率会导致热滞后使得失重曲线向高温区移动,不利于着火燃尽。3获得了中部烟叶在0、5%、10%氧气浓度下表观活化能随反应进程的连续变化曲线E_a(α),以及活化能分布函数f(E);E_a(α)随失重过程总体呈现先升后降的趋势,f(E)未呈现明显的高斯(Gaussian)分布特征;不同气氛下烟草材料活化能分布情况存在差异,在第二阶段易挥发的非聚合物组分的释放以及部分烟草聚合物初步受热分解和第四阶段半焦燃烧存在显著的动力学补偿效应。     

再造烟叶丝、膨胀烟丝和膨胀梗丝的燃烧特性

为了解再造烟叶丝、膨胀烟丝和膨胀梗丝的燃烧特性,利用锥形量热仪研究了三者在燃烧过程中热释放、烟气释放、质量损失、CO和CO2释放等关键燃烧特征参数的变化。结果表明:①膨胀梗丝的易燃性差于再造烟叶丝和膨胀烟丝;②在有焰燃烧阶段,膨胀烟丝较再造烟叶丝和膨胀梗丝具有更快速的烟气释放速率,而在阴燃阶段,膨胀烟丝的烟气释放速率明显低于再造烟叶丝;③在整个燃烧过程中,膨胀梗丝的发烟量均小于膨胀烟丝和再造烟叶丝。在阴燃阶段,再造烟叶丝的发烟量高于膨胀烟丝;④在阴燃状态下再造烟叶丝、膨胀烟丝和膨胀梗丝的CO释放速率都明显高于有焰燃烧阶段,CO2释放速率则相反;在整个燃烧过程中,膨胀梗丝较膨胀烟丝和再造烟叶丝生成了更多的CO和更少的CO2。     

二叔丁基过氧化物对生物柴油热解特性的影响

应用热重分析方法,研究二叔丁基过氧化物(DTBP)对地沟油生物柴油热解特性的影响。选取N2和O2作为反应气,温度从50℃升高至400℃,升温速率为20℃/min,绘制生物柴油样品的失重曲线和微商热重曲线,分析不同DTBP添加量的生物柴油热解过程的挥发特性和燃烧特性。结果表明:添加DTBP对生物柴油的挥发性影响较小;添加DTBP的生物柴油燃烧指数有所增加;DTBP能够有效促进燃料燃烧,使生物柴油具有更好的可燃性。     

小桐子油生物柴油的热解特性及动力学研究

利用热重分析仪在不同升温速率(10、20、30℃/min)和一定氮气(20 mL/min)条件下对小桐子油生物柴油的热解特性及动力学特性进行了研究。结果表明:小桐子油生物柴油热解过程主要分为低沸点组分挥发,各种脂肪酸甲酯的快速挥发和热解以及残留物缓慢分解失重三个阶段;升温速率增加使各个阶段的起始和终止温度均向高温区轻微移动,使热解失重率略微降低。动力学分析表明:小桐子油生物柴油的热解反应可用三个0.5级反应来描述,根据模型计算的活化能为10.10～85.73 kJ/mol,频率因子为1.82×10-3～1.45×108 min-1。     

导热填料改性烟草颗粒的热解和释烟特性

为揭示加热不燃烧状态下导热填料对烟草颗粒热解和释烟特性的影响规律,利用导热系数测试仪、热分析仪（TGA）和锥形量热仪（CONE）,研究了不同含量和种类的导热填料对烟草颗粒导热系数、热解过程以及烟气释放过程的影响。结果表明:①随碳酸钙（CaCO₃）粉体质量分数增加,烟草颗粒导热系数增大。20%添加量下填料发生自团聚,导热系数略有降低。晶须可有效改善填料在基材中的自团聚现象。碳化硅（SiC）较CaCO₃对导热系数的提升更明显。②相较于对照样品,添加导热填料后,烟草颗粒微分热重（DTG）曲线向低温区移动,整体上导热性越高,移动幅度越大,最大失重速率越大。不同升温速率下,具有最大导热系数样品的DTG曲线始终位于对照样的低温侧;且随升温速率增大,其与对照样热解特征参数的差值逐渐缩小,导热性差异对烟草颗粒热解过程的影响程度减小。③相较于对照样品,添加导热填料后,烟草颗粒起始释烟速率增大;随导热性提高,最大释烟速率增大,烟气释放过程集聚。CO与CO₂的释放速率随导热性提高明显增大,说明烟草颗粒的热解程度加剧,但提高导热性易造成热量集聚,使烟草颗粒发生燃烧。      

TG-FTIR联用研究HnB烟草基质在400℃以下的热解特性和气相产物

  目的  明确加热不燃烧（HnB）烟草基质热解特性和气相产物释放情况。  方法  采用热重-红外联用分析仪（TGFTIR）,在100 mL/min的空气流量和20℃/min的升温速率条件下,测试了甘油含量0~30%的烟草基质的热失重、气态产物组成随温度（30℃~400℃）的变化规律。  结果  ① 烟草基质主要的失重阶段处于130℃~360℃之间,该温度区间的失重速率极大值点有2个,1个处于200℃~235℃之间,另1个处于297℃~310℃之间。②烟草基质甘油含量在20%~30%时,150℃即释放出易挥发小分子,如:烟碱、碳水化合物、酚类和有机酸类、烷烃和烯烃类化合物等;甘油含量在0~10%时,200℃以上这些物质才会出现。③在4个失重阶段的失重速率极大值点附近温度下（100℃、200℃、300℃和400℃）,甘油含量对受热释放物中各类成分的比例产生了影响。  结论  上述规律可以为加热不燃烧卷烟的温度设计和烟草基质的甘油含量选择提供参考。      

烟草废弃生物质热解实验研究

采用热重分析方法,以氮气为载气对不同粒径烟梗、烟杆和玉米秸秆等生物质进行不同升温速率下的热解实验,分析出烟梗在不同条件下的失重情况,并与烟杆和玉米秸秆进行对比分析。研究显示:烟梗热解主要由水分析出,低沸点化合物析出,半纤维素、纤维素热解析出挥发分,木质素热解和生物炭的形成五个热重阶段组成。升温速率的提高会导致挥发分析出困难、峰值向高温区移动、而析出量增大;在相同的热解条件下,烟梗的热稳定性最好;随着粒径的减小,烟梗在低温区的热解持续时间缩短,热解能力变差,析出挥发分减少。     

煤与生物质（稻秸秆）共热解反过程及协同性研究

利用综合热分析仪,对煤(烟煤、无烟煤)与稻秸秆按不同比例混合及各自单独热解反应进行了热解实验.结果表明:生物质与煤的热解过程可简化看作是在较低温度段(400℃以下)热解以生物质为主;在高温段(600～850℃)热解以煤为主.生物质对煤的热解过程有促进作用,随着生物质掺混比例的上升,煤的热解高峰区的温度向低温区移动.但是促进程度随着生物质的量的增加而减小,并且对烟煤的促进作用要比对无烟煤的作用明显.对无烟煤与稻秸秆(质量比3:2)的混合物按升温速率分别为10℃/min和20℃/min的热解过程作了对比实验,得出升温速率加快会造成混合物热解反应所需的温度升高和热解产物余量增加的结论.     

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.     

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.     

Influence des ions sur le pouvoir hydratant de l'ure e: e tude sur peau de porc ex vivo

This study deals with the influence of ions (NaCl and MgSO4) in a W/O emulsion containing 10% urea. Moisturization kinetics are assessed by corneometry on pig skin ex vivo. The formula's influence on urea penetration is measured by infrared spectrometry with an ATR device and the stripping method. Corneometry and spectroscopy were chosen to record simultaneously the hydratation levels and urea localization into superficial cell layers. Urea crystallization after evaporation of emulsions and aqueous solutions is described. Results show that urea does not hydrate nor penetrate when applied to the skin through an aqueous gel. In a W/O emulsion, sodium chloride increases the ability of urea to moisturize without improving penetration. In vitro urea crystallization is disturbed by sodium chloride or magnesium sulphate for solutions and emulsions. This stabilization by ions is correlated with good moisturization values. The stabilization of urea in the solute state provided by ions increases its water epidermal binding capacity without enhancing penetration.     

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.