胶原蛋白纺丝溶液的流变性能

研究了胶原纺丝溶液的流变学性质,讨论了浓度、温度对胶原流变特性的影响。结果表明:随着浓度的增大,胶原蛋白溶液的弹性模量(G')、粘性模量(G')和复数粘度(η*)都有提高,并且出现假固态行为,当胶原蛋白溶液浓度大于0.75%以后胶原蛋白溶液的粘弹性突然成数量级增大,另外胶原蛋白溶液的内耗(tanδ)随着溶液浓度的升高而增大,在浓度为0.75%的时候达到最大值而后逐渐减小;随着温度的升高,胶原蛋白溶液的G'、G'和η*都降低,而tanδ升高,并且表现出假液态行为,当温度低于25℃时,胶原蛋白溶液的各种性能变化并不明显,当温度升高到32.5℃时,G'、G'、η*和tanδ突然降低到很小的值且缺乏规律性,表明在该温度下胶原的天然结构已经被破坏。     

金钱菇多糖的流变学性质研究

从金钱菇子实体水提残渣中纯化获得了一个多糖组分JQPs,采用DHR-3型旋转流变仪研究了JQPs溶液流变学性质,为其在食品工业中的应用提供理论支持。静态流变学实验结果表明,JQPs溶液流动指数n1,为假塑性流体,浓度越高其假塑性越明显。通过对溶液流动曲线的拟合,发现幂律方程可以作为描述JQPs溶液流动曲线的模型;动态粘弹性实验表明JQPs溶液的G'和G″在1~100rad/s扫描频率下与测试浓度和测试温度均具有一定的相关性。一定温度下,随着浓度的增加,G'的增加速率超过G″,当浓度达到2.0%时曲线重合,开始形成弱凝胶。浓度为2.5%的JQPs溶液的G'和G″随着温度的升高而逐渐减小,在15℃时基本重合,开始形成弱凝胶。     

超声时间对胶原溶液流变性能的影响

5 mg/m L胶原溶液在超声条件为20 k Hz、45 W时分别处理0、5、10和30 min后,采用流变仪考察其稳态剪切、动态黏弹性、触变和蠕变性能的变化。结果表明:胶原溶液均表现出明显的假塑性,其流变学性能在超声处理10 min时已发生了显著改变,超声10 min后改变速率减缓。在超声处理10 min时和未超声处理的胶原相比,动态频率0.1 Hz处的弹性模量(G')、黏性模量(G")及复数黏度(η*)下降均超过了70%,力学损耗(tanδ)增加了42.91%,触变环面积和应变回复率分别下降了88.86%和92.56%,最大柔量增加了24.88倍。经超声处理后胶原溶液中分子的缠结程度降低,抵抗形变能力变弱,溶液的流动性能增强。     

虾夷扇贝生殖腺凝胶状酶解物的流变特性

本文对虾夷扇贝生殖腺凝胶状酶解物的流变特性进行了研究,为虾夷扇贝的综合利用奠定研究基础。以虾夷扇贝雄性生殖腺为原料,选用木瓜蛋白酶作为工具酶,通过SDS-PAGE分析酶解过程中蛋白质分子量的变化,利用流变仪考察酶解液的流变特性;利用脱氧核糖核酸酶(DNaseⅠ)在前期对样品进行孵育,探讨DNA分子对于其流变特性的作用影响。结果显示,虾夷扇贝雄性生殖腺经木瓜蛋白酶(30000 U/g蛋白)酶解15~180 min后,蛋白质发生显著降解。在不同流变仪扫描模式下,酶解液的储存模量G'、损耗模量G″、黏度η、复数黏度η*均明显高于未酶解样品。酶解3 h时,应变扫描中,应变为1%时,G'、G″分别达到了188.9 Pa和17.9 Pa;频率扫描中,频率为0.1 Hz时,η*达到230.9 Pa·s。经DNaseⅠ处理后,酶解液流变参数(G'、G″及η*)显著降低,但略高于未酶解样品。上述结果说明,虾夷扇贝生殖腺凝胶状酶解物以弹性占主导,具有明显的剪切稀化现象,且其流变特性可能与肽分子和DNA分子有关。     

淀粉纳米颗粒在不同增塑剂中的糊化与流变特性研究

本文以蜡质玉米淀粉为原料,经普鲁兰酶酶解脱支,短直链淀粉重结晶制取淀粉纳米颗粒(SNPs)。采用差示扫描量热仪(DSC)和动态流变仪,探究了不同浓度SNPs在甘油、山梨糖醇、葡萄糖水溶液中的热特性、回生特性以及流变特性的变化规律。DSC测试表明,添加山梨糖醇、葡萄糖和甘油溶液(其与水比例为1:1)后,SNPs的起始糊化温度分别增加了10.85℃、10.96℃和15.02℃,SNPs的终止糊化温度分别增加了9.29℃、9.17℃、12.40℃。回生结果表明,增塑剂会抑制SNPs的回生。随着浓度增加,SNPs在增塑剂体系中储能模量明显增加,且损耗模量大于储能模量,凝胶性增强。20%SNPs在山梨糖醇溶液和甘油溶液中的储能模量是10 Pa·s左右,而在葡萄糖溶液中大于1000 Pa·s,在葡萄糖溶液中损耗模量在100~500 Pa·s,说明SNPs葡萄糖水溶液具有更强的凝胶性。本文为SNPs在不同增塑剂中制备可降解膜提供理论依据。     

盐对不同直链含量玉米淀粉理化特性及流变学特性的影响

分析了盐对不同直链含量玉米淀粉的理化特性及流变学特性的影响。结果表明,盐抑制了淀粉颗粒的膨胀,盐浓度越大,抑制作用越强。盐质量浓度为0 g/100 mL的蜡质淀粉和普通淀粉膨胀势在65℃到75℃迅速增加,2.0 g/100 mL时膨胀势在75℃到85℃迅速增加且幅度最小。蜡质淀粉和普通淀粉DSC图谱呈G峰和M2峰,高直链淀粉呈G峰。盐提高了凝胶化起始温度,蜡质淀粉从50.1℃增加到90.2℃,普通淀粉从56.6℃增加到99.6℃,高直链淀粉从98.8℃增加到105.7℃。盐也抑制了淀粉的糊化进程,盐浓度越大,糊化温度越高。普通淀粉的储存模量G',损耗模量G"和表观黏度η大于蜡质淀粉。普通淀粉和蜡质淀粉在低盐浓度(0.6g/100 mL)下的G'、G"和η值均大于高盐浓度(2.0 g/100 mL)。     

超声对大豆11S蛋白-葡聚糖共混溶液冷致凝胶流变性质的影响

本文采用稳态剪切和小变形振荡流变分析方法研究了超声时间、超声功率对大豆11S蛋白-葡聚糖共混溶液的稳态剪切粘度和及其冷致凝胶过程动态流变性质的影响。实验结果表明：对照样及超声处理后的共混溶液均为假塑性流体,共混溶液的表观粘度随超声时间或超声功率增加呈降低趋势。与对照样相比,经237.5 W超声处理6 min后,粘度的下降幅度达46.6%。当超声处理时间或功率分别位于0~9 min或0~142.5 W范围时,共混溶液经超声处理后均可冷致形成非共价三维网络共混凝胶,凝胶的G'和G"随时间或功率增加呈增加趋势。当超声时间或功率分别增加到12 min或237.5 W时,共混凝胶的G'分别由峰值的954.7 Pa和609.9 Pa降低为367.3 Pa和507.8 Pa,同时凝胶起始时间被迟滞。超声处理对凝胶线性粘弹区域影响不显著。     

啤特果果汁流变学特性研究

为掌握啤特果果汁的流变学特性,试验对啤特果果汁的流体类型、模量以及温度和可溶性固形物对黏度的影响进行了研究。结果表明,在25、35、45、55、65℃条件下,啤特果果汁的流变曲线方程拟合参数n值<1,属于假塑性流体,其储能模量G′大于损耗模量G″;Arrhenius方程η=Ke-E a/R T对温度与黏度的拟合参数R 2>0.99,在25~65℃黏度由0.0013 Pa·s降低至0.0006 Pa·s,其中在30.7℃时黏度最大,在65℃时黏度最小;可溶性固形物含量对黏度的影响符合指数方程η=Kexp(A C),可溶性固形物含量增加黏度随之增加,其中25℃、可溶性固形物含量为32°Brix时,黏度最大。研究结果为啤特果果汁的加工利用提供了依据。     

食用植物油流变学特性研究

采用旋转流变仪探讨了15种植物油和13种不同品牌花生油流变学特性.结果表明:食用植物油的黏度(η)不随剪切速率的增大而改变,均属于牛顿型流体,橄榄油黏度最大(0.065 50 Pa·s),其次是茶油,葡萄籽油黏度最小(0.047 80 Pa·s);植物油黏度随温度的升高而减小,其流变学特性为温度敏感;除花生油外,其余植物油的lnη与1/T在0～50℃范围内有良好线性关系(r≥0.999 4),13种花生油黏温曲线(lnη与1/T)均为非线性相关.     

3种纯度酵母甘露聚糖的流变学性质

目的:研究纯度对酵母甘露聚糖(YM)溶液的表观黏度(η)和动态粘弹性(G′,G″)的影响。方法:利用MCR301流变仪测定3种纯度YM的静态和动态流变学性质。结果:通过水提醇沉、木瓜蛋白酶、链霉蛋白酶处理,分别得到YM1、YM2、YM3样品,其纯度依次升高。在剪切速率0.1~100/s范围,YM1、YM2的η逐渐下降,YM3基本不变。在相同剪切速率下,YM1、YM2的η高于YM3。在5~85℃范围,η均逐渐下降,其中,YM2的黏度受温度影响最弱;恒温条件下,YM1、YM2呈剪切变稀趋势,非牛顿指数(n)分别在0.23~0.30,0.35~0.41范围,其中YM1的非牛顿性始终强于YM2;5℃下,YM3的n为0.914,为假塑性流体。初始添加盐离子引起η下降,继续添加,3种样品η没有显著变化。在扫描频率范围,YM2样品的G′始终高于YM1,当频率高于10/s时,YM1与YM2的凝胶结构被破坏。结论:YM的纯度提高时,溶液由假塑性流体转化为牛顿流体,影响其在外界条件下的流变学性质。以上结果为YM的功能化结构设计奠定理论基础。     

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