大豆分离蛋白在不同pH下的拉曼光谱分析

分析了不同pH下大豆分离蛋白溶液拉曼光谱,结果表明:随着pH的增大,α-螺旋结构含量增加,无规卷曲结构含量降低,色氨酸残基由"埋藏式"逐渐转变为"暴露式"。在所测定的pH范围内(pH6.5～9.0)大豆分离蛋白的酪氨酸残基趋向于"暴露式"。pH对二硫键的构型的改变则表现出一种非线性改变趋势。     

微射流对野生黑豆蛋白结构及功能性的影响

探究微射流(0、42.5、89.0、123.5、152.0、175.5 MPa)作用下野生黑豆蛋白结构变化规律,研究表明:微射流处理促进了野生黑豆蛋白质分子间的疏水交互作用,蛋白中的不稳定聚集体逐渐分解成小分子可溶性聚合物,而在超过123.5 MPa时,高强度的剪切作用使可溶性蛋白重新聚合,其乳化性随均质压力增加先增大后减小,乳化稳定性变化不显著(P0.05)。拉曼光谱分析结果表明:与未处理野生黑豆蛋白相比,微射流均质处理下所有蛋白均发生了α-螺旋结构相对含量增加和β-折叠结构相对含量减少的现象。拉曼光谱在760 cm-1色氨酸归属峰处强度降低,表明均质处理使野生黑豆蛋白发生了部分的解折叠,蛋白表现为"暴露"态。均质处理下酪氨酸归属峰强度显著增加,表明微射流均质处理改变野生黑豆蛋白酪氨酸的微环境。拉曼归属谱带强度随着均质压力的增加而增大,使二硫键的t-g-t型构象转化为g-g-t型构象。     

不同品种大豆分离蛋白体外消化产物的结构特性

以我国5种大豆分离蛋白(SPI)为基础原料,运用多种蛋白分析检测手段,研究这5种大豆分离蛋白结构对体外模拟消化特性的影响。结果表明:大豆分离蛋白及消化产物的红外光谱、拉曼光谱分析二级结构元素含量变化规律基本一致,α-螺旋结构、β-折叠结构与DH呈现一定相关性。5种大豆分离蛋白样品及其消化产物的酪氨酸残基趋向于"暴露式",随着消化时间的延长,λmax整体上增大,拉曼色氨酸侧链归属谱带强度随消化时间的延长逐渐降低,表明色氨酸残基趋向于亲水性微环境。5种大豆分离蛋白经连续5 h的体外模拟消化试验,水解度DH随着消化时间的延长而增加,当消化时间超过1 h后,DH的增加速度减慢,而在相同条件下不同样品DH存在差异性。     

单宁酸与大豆分离蛋白相互作用研究

利用荧光光谱、紫外光谱和圆二色谱,从分子水平研究单宁酸与大豆分离蛋白的相互作用。结果表明:单宁酸对大豆分离蛋白有较强的荧光猝灭作用,当单宁酸浓度小于6×10~(-6)mol/L(相对于大豆分离蛋白质量分数5. 1%)时,猝灭类型为静态猝灭,当单宁酸浓度大于6×10~(-6)mol/L时,同时存在静态猝灭和动态猝灭;单宁酸通过疏水作用与大豆分离蛋白结合,导致大豆分离蛋白的色氨酸和酪氨酸残基微环境亲水性增强,但对大豆分离蛋白的二级结构没有显著影响。     

高压微射流处理对大豆分离蛋白结构功能特性及其乳液性质的影响

采用高压微射流技术在不同压力条件下对大豆分离蛋白(SPI)进行处理,分析处理前后SPI结构、功能特性以及乳液性质的变化。结果表明:低压均质处理可使SPI的粒径降低,当均质压力增加至一定程度时,蛋白间的相互作用增加,颗粒粒径增加;均质压力在0～95 MPa范围内随着压力逐渐升高,SPI的溶解性得到了显著改善,而当均质压力增加到125 MPa和155 MPa时,溶解性反而降低;高压均质处理对乳化性的影响与溶解性变化趋势基本吻合;表面疏水性随着压力的增大而增大;内源荧光光谱结果表明,随着均质压力的增大,最大吸收波长红移,荧光强度降低,色氨酸残基暴露于极性环境中; SPI乳液粒径随着均质压力的增大(95 MPa除外)整体依次变小,SPI乳液在压力65 MPa处理时油脂氧化速率最快,SPI乳液在压力125、155 MPa处理时的初级氧化速率要低于未处理的乳液。     

大豆7S球蛋白结构特性与表面疏水性相关性研究

以具有代表性的6个大豆品种制备的大豆7S球蛋白为研究对象,采用ANS荧光探针法测定表面疏水性,Ellman试剂分析法测定巯基和二硫键含量,激光拉曼光谱和荧光光谱分析空间构象,探讨大豆7S球蛋白结构特性与表面疏水性的相关性。结果表明:大豆7S球蛋白的表面疏水性与二级结构的α-螺旋含量和β-折叠含量呈负相关,与二级结构的β-转角含量和无规则卷曲含量呈正相关;与色氨酸残基荧光峰λ_(max)呈正相关,与拉曼光谱色氨酸费米共振I_(1360)/I_(1340)值呈负相关,与拉曼光谱酪氨酸费米共振I_(850)/I_(830)值呈正相关,与暴露的酪氨酸残基克分子数呈正相关,与N_(暴露)和N_(包埋)的比值呈正相关;与暴露巯基含量、巯基暴露程度呈正相关,与游离巯基含量、二硫键含量、二硫键构象的相关性均不显著。     

高压均质协同壳聚糖萃取对乳清水中大豆蛋白结构和功能性的影响

本研究以大豆乳清水为原料,研究高压均质协同壳聚糖法对大豆乳清水中大豆蛋白回收的影响,并研究其对回收蛋白的结构及功能特性的影响。结果表明,当蛋白/多糖质量比为2:1时,与未高压均质处理相比,在高压均质压力不大于90 MPa条件下,高压均质协同壳聚糖处理使蛋白回收率显著增加（P<0.05）,达到61.92%;另外,拉曼光谱和荧光光谱显示,在高压均质压力不大于90 MPa条件下,随着高压均质压力的逐渐升高,大豆分离蛋白的α-螺旋和β-折叠含量呈现降低趋势,无规卷曲含量呈现增加趋势,荧光强度和λ_max呈现增加趋势,表明经高压均质后混合体系的微环境发生了改变;且回收蛋白的溶解性、乳化活性及乳化稳定性逐渐增加,浊度逐渐减少。当高压均质压力大于90 MPa时,随着高压均质压力的逐渐升高,蛋白质分子荧光强度和λ_max降低,回收蛋白的溶解性、乳化活性及乳化稳定性的逐渐增加速率逐渐减少。该研究可为工业化生产大豆分离蛋白废水的处理和副产物资源化利用提供理论指导。     

高压微射流对大豆分离蛋白化学性质及结构的影响

采用高压微射流技术处理大豆分离蛋白,并对其化学性质及结构变化进行了研究。结果表明,大豆分离蛋白经过高压微射流均质,在40,80,120和160 MPa下处理后,其溶解度、泡沫稳定性和持油性均得到了改善,但乳化性、持水性能变差。傅里叶变换红外光谱图显示,经高压微射流技术处理后的大豆分离蛋白二级结构发生变化。扫描电镜显示,高压微射流技术在0.1~120 MPa的压力范围内会使大豆分离蛋白颗粒破碎,且破坏程度随着压力的增加而加剧,但当压力达到160 MPa时,颗粒聚集的速度高于破碎的速度,颗粒尺寸稍微变大。高压微射流影响了大豆分离蛋白的结构,从而影响了化学性质,为其在食品工业中的应用提供了理论依据。     

低压均质处理对大豆分离蛋白凝胶特性的影响

通过测定凝胶的持水性、黏性、巯基含量,运用扫描电子显微镜、质构测定等方法分析探讨了低压均质处理(0～40 MPa)对大豆分离蛋白(Soy protein isolate)凝胶特性和结构的影响。结果表明,随着均质压力的增大,大豆分离蛋白内部疏水基团暴露,分子结构逐渐展开,当均质压力达到20 MPa时,疏水相互作用促进了凝胶网状结构的形成,有效提高了凝胶的弹性、回复性、黏性。扫描电子显微镜结果表明,当均质压力达到20 MPa时,凝胶结构规律,致密有序;当压力进一步增大时,产生的不溶性聚集体破坏了凝胶的网状结构,产生不均匀的空穴,立体感差。     

超高压对扇贝界面闭壳肌结构的影响

为研究超高压技术的脱壳效果及其对扇贝界面闭壳肌（贝壳与闭壳肌接触面以上2 mm厚度的闭壳肌段）结构的影响,首先测定经超高压处理后扇贝的脱壳率,再利用拉曼光谱和扫描电子显微镜分析超高压作用下扇贝界面闭壳肌结构变化的规律。结果发现,超高压作用对扇贝界面闭壳肌蛋白质的主链结构和侧链结构产生了较大的影响,尤其在200、300 MPa的压力下,扇贝界面闭壳肌拉曼光谱各位置的特征峰强度有所增大,但蛋白质变性程度并不非常明显;当压力大于200 MPa时,酪氨酸残基苯环上—OH的氧原子由氢键的供体逐渐转变为受体,I850 cm－1/I830 cm－1减小,色氨酸残基逐渐由包埋状态向极性环境中暴露,二硫键的构象被还原。综上,超高压技术对扇贝界面闭壳肌的结构产生了一定影响,实验结果能为扇贝乃至贝类产品的工业化生产提供参考。     

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