表没食子儿茶素没食子酸酯与燕麦β-葡聚糖复合物的形成及表征

多酚与膳食纤维间可通过相互作用形成复合物,为了探究多酚与膳食纤维间的相互作用机制及其所形成复合物的结构和形态,本文选用表没食子酸儿茶素没食子酸酯(Epigallocatechin gallate,EGCG)和燕麦β-葡聚糖为原料制备复合物并对其结构进行表征.结果表明:EGCG与燕麦β-葡聚糖复合物的形成与EGCG浓度和...     

多酚对平欧榛仁分离蛋白凝胶特性及体外消化特性的影响

多酚与蛋白质结合能够影响蛋白质凝胶特性,进而影响食品的质地。以平欧榛仁分离蛋白(hazelnut protein isolate, HPI)为原料,将茶多酚(tea polyphenol, TP)、表没食子儿茶素没食子酸酯(epigallocatechin gallate, EGCG)、没食子酸(gallic acid, GA)等3种多酚分别与HPI结合,探讨3种多酚对HPI结构性质、凝胶特性、凝胶结构性质、蛋白质消化率及消化产物抗氧化性的影响。结果表明,3种多酚均可促进HPI结构展开,通过疏水相互作用和氢键与HPI结合。TP、EGCG、GA的加入使HPI凝胶硬度分别提高了47.77%、59.87%、10.76% (P<0.05);凝胶持水性分别提高了37.20%、39.74%、28.17% (P<0.05)。与HPI凝胶、HPI-TP凝胶、HPI-GA凝胶相比,扫描电镜观察结果显示,HPI-EGCG凝胶微观结构更为致密;凝胶流变学特性分析结果显示,HPI-EGCG储能模量更高;傅里叶变换红外光谱显示,HPI-EGCG凝胶氢键作用更强、β-折叠含量更高,凝胶硬度和持水性更好。凝胶分子间作用力分析结果显示,氢键和二硫键是维持HPI-TP凝胶和HPI-EGCG凝胶的主要作用力,疏水相互作用和二硫键是维持HPI-GA凝胶的主要作用力。与HPI凝胶、HPI-TP凝胶、HPI-GA凝胶相比,HPI-EGCG凝胶中游离巯基含量更低、二硫键含量更高,凝胶结构更稳定。经体外消化后,TP、EGCG使HPI凝胶蛋白质消化率降低,GA使HPI凝胶蛋白质消化率增加(P<0.05)。4种凝胶中,HPI-EGCG凝胶消化产物抗氧化性更强(P<0.05)。多酚能够有效改善HPI的凝胶特性并保留其抗氧化性,其中HPI-EGCG凝胶具有较佳的凝胶特性和消化产物抗氧化性。希望研究结果可为新型平欧榛仁分离蛋白凝胶产品的开发和利用提供理论依据。     

表没食子儿茶素没食子酸酯和米糠蛋白的相互作用

采用荧光光谱和紫外-可见光谱法研究表没食子儿茶素没食子酸酯(Epigallocatechin gallate,EGCG)和米糠蛋白(Rice bran protein,RBP)之间的相互作用。结果表明:EGCG对RBP有较强的荧光猝灭作用,为且动态和静态混合淬灭。EGCG与RBP在290、300、310 K时相互作用的表观结合常数分别为1.322 8×10~6、1.504 2×10~6、1.817 6×10~6 L/mol,对应的结合位点数分别为1.387 8、1.327 0、1.377 0。同步荧光光谱、紫外-可见光谱和三维荧光光谱表明EGCG主要影响RBP色氨酸残基空间结构的微环境,使其周围的疏水性下降。热力学参数表明EGCG与RBP结合的主要作用力为疏水相互作用。根据F?ster非辐射转移理论计算了不同条件下EGCG与RBP结合距离r为0.800 4 nm。建立了不同温度下EGCG与RBP结合率的理论模型,发现RBP的结合率随着EGCG浓度增大而减小,温度对两者的结合率无显著影响。     

EGCG与β-伴大豆球蛋白/大豆球蛋白相互作用对蛋白质结构的影响

采用荧光光谱、紫外-可见光谱、傅里叶变换红外光谱和分子对接方法,研究中性条件下β-伴大豆球蛋白（β-conglycinin,7S）、大豆球蛋白（glycinin,11S）与表没食子儿茶素没食子酸酯（(–)-epigallocatechin-3-gallate,EGCG）的相互作用。结果表明,在中性条件下EGCG与7S/11S蛋白之间存在相互作用,并诱导了氨基酸残基微环境发生变化。EGCG通过动态和静态方式猝灭7S/11S蛋白内源荧光。与7S蛋白相比,EGCG对11S蛋白的亲和力更高。EGCG与7S/11S蛋白的反应自发进行,两者主要通过氢键和范德华力形成物质的量比1∶1的复合物。EGCG能够降低7S/11S蛋白的表面疏水性,并随着EGCG浓度的增加,11S蛋白变化更加明显。傅里叶变换红外光谱和分子对接研究表明除氢键外,疏水相互作用也参与了复合物的形成。EGCG结合导致7S/11S蛋白二级结构发生不同变化,使蛋白质发生解折叠。     

2 种天然抗氧化剂与鲢鱼肌球蛋白的相互作用

研究2 种天然抗氧化剂表没食子儿茶素没食子酸酯（epigallocatechin gallate,EGCG）、白藜芦醇（resveratrol,RE）与鲢鱼肌球蛋白之间的相互作用。采用荧光光谱与圆二色谱技术分别探究EGCG、RE与鲢鱼肌球蛋白分子间相互作用的结合情况和其对肌球蛋白微观结构的影响。荧光光谱结果表明：EGCG、RE与鲢鱼肌球蛋白之间发生相互作用均会导致肌球蛋白荧光猝灭现象的发生,且荧光猝灭方式都为静态猝灭。通过热力学数据分析得出EGCG、RE与肌球蛋白分子结合的主要作用力是氢键和范德华力;并利用Stern-Volmer方程处理数据得到EGCG、RE与肌球蛋白在不同温度条件下的结合常数和结合位点数。圆二色谱及表面疏水性结果表明,EGCG、RE诱导了肌球蛋白结构的变化,EGCG使肌球蛋白α-螺旋相对含量增加,表面疏水性降低;而RE对肌球蛋白二级结构无明显作用,但会使其表面疏水性增加。     

去折叠态β-乳球蛋白与表没食子儿茶素没食子酸酯的相互作用

通过微波处理β-乳球蛋白（β-lactoglobulin,β-LG）得到去折叠态β-乳球蛋白（unfolded-β-lactoglobulin,U-β-LG）,采用荧光光谱、紫外-可见光谱、圆二色光谱的方法研究表没食子儿茶素没食子酸酯（epigallocatechin gallate,EGCG）与U-β-LG的相互作用机制。结果表明,EGCG能与β-LG和U-β-LG相互作用形成复合物。它们相互之间均主要为疏水作用力。在298?K时,EGCG与β-LG和U-β-LG的结合距离分别为3.188?nm和2.875?nm。EGCG的结合使β-LG和U-β-LG的二、三级结构发生变化,表面疏水性降低。与天然β-LG相比,U-β-LG与EGCG具有更大的结合强度,结合后的U-β-LG发生更大的结构变化。     

没食子酸与猪血红蛋白的相互作用及对其稳定性的影响

猪血红蛋白(Porcine hemoglobin,PHb)的结构在一定理化因素(温度、pH)条件下稳定性较差,可能会出现亚铁血红素损失及蛋白质变性等现象。没食子酸(Gallic acid,GA)作为一种天然抗氧化剂,与PHb作用能影响PHb的结构稳定性。文章探讨了不同温度、pH条件下添加GA对PHb结构稳定性的影响,采用荧光光谱法研究了GA和PHb在模拟生理条件下的作用机制。结果表明,GA能一定程度提高PHb的热稳定性和酸稳定性。GA对PHb的内源荧光的淬灭方式为动态淬灭,298 K下的结合常数为0.70/104 M-1,PHb上仅有一个GA结合位点。疏水相互作用为GA与PHb之间的主要作用力,两者之间反应可自发进行。该研究可为GA在肉制品中的应用提供理论依据。     

EGCG与乳清蛋白相互作用的光谱分析

探究表没食子儿茶素没食子酸酯(epigallocatechin gallate,EGCG)与乳清分离蛋白(whey protein isolate,WPI)间的相互作用。测定不同pH值与不同离子浓度条件下WPI的紫外吸收光谱、导数光谱和荧光光谱,利用SternVolmer方程判断荧光猝灭机制,采用位点结合模型公式计算结合常数和结合位点数。结果表明,紫外吸收光谱和导数光谱结果显示EGCG改变了WPI中酪氨酸和色氨酸残基所处的微环境,使WPI的分子构象发生了变化。荧光光谱结果显示EGCG可以有规律地猝灭WPI的内源荧光,猝灭机理为静态猝灭,EGCG与WPI结合常数在pH 2.0~9.0范围内随pH的增大先减小后增大,在离子浓度0.10 mol/L^0.20 mol/L范围内随离子浓度的增大而增大,结合位点数约为1。EGCG与WPI间存在静电相互作用。     

基于酪蛋白酸钠/EGCG/阿拉伯胶自组装构建EGCG纳米粒及其形成机制研究

本文通过酪蛋白酸钠(sodium caseinate、SC)、表没食子儿茶素没食子酸酯(epigallocatechin gallate、EGCG)和阿拉伯胶(gum arabic、GA)三者自组装构建EGCG纳米粒(SC-EGCG-GA纳米粒),研究形成高载药量且稳定性好的纳米粒的条件,并考察纳米粒的贮藏稳定性,同时采用透射电子显微镜(transmission electron microscope、TEM)对纳米粒的微观形貌进行表征,最后借助红外光谱(fourier transform infrared spectroscopy、FTIR)、荧光光谱和圆二色谱(circular dichroism、CD)对纳米粒结构进行表征,探讨纳米粒形成机制。结果发现,形成高载药量且稳定性好的SC-EGCG-GA纳米粒的条件为EGCG/SC/GA浓度比2:5:5,SC和GA总浓度1.5 mg/mL,pH4.2,NaCl浓度10 mmol/L。此时形成的纳米粒粒径约为173.52 nm,Zeta电位约为-19.94 mV,包封率约为62.82%,载药(EGCG)量达到338.49 μg/mg,在4 ℃下贮藏30 d后仍保持稳定。透射电镜结果显示纳米粒呈球形。根据FTIR、荧光光谱和CD结果,推测纳米粒可能的形成机制为首先SC与EGCG通过氢键结合,GA加入后SC中的NH₃+和GA中的COO-则通过静电相互作用结合,从而抑制SC与EGCG过度结合与聚集,三者通过以上非共价作用自组装形成纳米粒。     

酪蛋白酸钠和阿拉伯胶相互作用的研究及纳米粒的制备

通过对酪蛋白酸钠(SC)与阿拉伯胶(GA)复合体系浊度、粒径和Zeta电位的表征来研究p H、SC/GA浓度比、SC与GA总浓度和离子强度(Na Cl浓度)对两者相互作用及纳米粒形成的影响,利用透射电镜(TEM)表征纳米粒的微观形貌,并对纳米粒的贮藏稳定性进行考察,最后借助红外光谱(FTIR)和荧光光谱探讨SC与GA相互作用形成纳米粒的机制。结果发现:p H、离子强度可显著影响SC和GA两者相互作用及纳米粒的形成,表明两者形成纳米粒的主要作用力是静电相互作用。同时得到SC和GA相互作用形成稳定纳米粒的条件为:SC/GA浓度比1∶1,p H4.2,SC与GA总浓度3.0 mg/m L,Na Cl浓度10 mmol/L。在此条件下形成的纳米粒粒径约为142 nm,Zeta电位约为-21.43 m V,于4℃贮藏30 d后仍保持稳定。TEM结果显示纳米粒呈球形。FTIR证实两者之间的静电相互作用发生在SC中的-NH+3和GA中的-COO-之间。荧光光谱表明SC和GA通过静电相互作用形成纳米粒的结合是低亲和性的。     

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.