罗汉果多糖的结构研究

用热水从罗汉果(Siraitia Grosvenorii)中提取所得的粗多糖,经DEAE-Cellulose、Sephadex G-200柱层析得到1个纯罗汉多糖SGPS1;利用HPLC、GC、GC-MS、13C NMR、甲基化、高碘酸氧化、Smith降解、部分酸水解等方法分析了SGPS1的组成和结构.结果表明,多糖SGPS1为酸性杂多糖,它由鼠李糖、阿拉伯糖、木糖、半乳糖、葡萄糖和葡萄糖醛酸组成,各糖残基的摩尔比为Rha∶ Ara∶ Xyl∶ Gal∶ Glc∶ GlcA=1.00∶ 2.30∶ 1.40∶ 9.07∶ 39.53∶ 2.46;SGPS1由(1→4) Glc、(1→3)Gal构成主链,且以(1→4)Glc键型为主,Glc在2-O、3-O和6-O处有分支,Gal在6-O处有分支,平均每20个主链糖残基有5个分支糖残基;侧链由(1→3)Glc、(1→6)Glc、(1→4)Gal和(1→2)Rha片段组成;Ara、Xyl以及部分Glc、Gal为末端基;GlcA在分子中是以末端GlcA和3-位取代的GlcA的形式存在.     

鹿蹄橐吾多糖LW21的分离纯化及其结构分析

目的:确定鹿蹄橐吾多糖LW21的结构,为探讨鹿蹄橐吾多糖的药理活性,合理利用鹿蹄橐吾这种植物资源提供依据。方法:水提取醇沉获得鹿蹄橐吾水溶性粗多糖LW,经酸性乙醇分级和DEAE-SephdexA-25纯化得多糖LW21。纸层析、醋酸纤维薄膜电泳和Sepharose CL-4B柱层析进行纯度鉴定,LW21结构分析采用高碘酸氧化、Smith降解、甲基化分析及IR、NMR、GC和GC-MS等方法。结果表明:LW21为均一多糖,相对分子质量约为1.1×106。其单糖组成为鼠李糖(Rha)、阿拉伯糖(Ara)、甘露糖(Man)、葡萄糖(Glc)、半乳糖(Gal),物质的量比为7.4:11.9:25.7:40.0:14.9。多糖LW21为有分枝结构,主链由Glc和Man构成,其中其中Man主要以β(1→2)和β(1→6)糖苷键连接,β(1→2)糖苷键在3-O处和6-O处有分枝,β(1→6)糖苷键在2-O和4-O处有分枝,Glc也主要以β(1→2)及β(1→6)糖苷键连接,β(1→2)糖苷键在6-O处有分枝,β(1→6)糖苷键连接,在2-O处有分枝。分子支链由Ara、Rha、Gal构成。末端残基为Gal、Ara、Rha、Glc。结论:鹿蹄橐吾多糖LW2 1是一新结构多糖,为首次从鹿蹄橐吾中分离得到。     

降血糖南瓜寡聚糖的结构表征及构效关系初探

探讨具有降血糖作用的南瓜寡聚糖的分子组成、分子结构信息与其活性间的构效关系。以南瓜粉为原料,经水提取、有机溶剂分步萃取和柱色谱分离纯化,得到1种水溶性寡聚糖(PCE-CGL)。经高碘酸氧化、Smith降解,采用IR,NMR等方法对该多糖的化学结构进行表征。结果表明,PCE-CGL分子质量为5.030×103u,主要由葡萄糖、半乳糖和肌醇组成,物质的比为6∶1∶2,并含有少量的氨基糖。主链主要是以β-1→4糖苷键及β-1→3糖苷键连接的葡萄糖、半乳糖、葡萄糖胺及肌醇,侧链主要是以β-1→2糖苷键及α-1→6糖苷键连接的葡萄糖。提示PCE-CGL很可能作为胰岛素化学介体的类似物,通过增加化学介体的数量来改变胰岛素敏感的酶的活性,从而实现其生物学效应。     

芜菁水溶性多糖的结构分析

采用水提醇沉的方法提取芜菁粗多糖,经酸性乙醇分级和DEAE-52、Sephadex G-100纯化得芜菁多糖WJdp4-b。采用Sepharose CL-4B柱层析、HPLC法检测WJdp4-b的均一性,通过纸层析(PC)、气相色谱(GC)、红外光谱(IR)、核磁共振(NMR)、部分酸水解、高碘酸氧化和Smith降解、甲基化分析等分析方法对WJdp4-b的结构进行解析。结果表明:WJdp4-b为均一性多糖,相对分子质量约为10 840。其单糖组成为鼠李糖(Rha)、阿拉伯糖(Ara)、甘露糖(Man)、葡萄糖(Glc),各单糖的摩尔比为1.0∶1.0∶10∶9.0。结构分析表明:WJdp4-b为多分支结构,分子的主体是由Glc构成,连接方式为,Glc以1→3链接构成了WJdp4-b的主链,在Glc的6位处有分支,每17个Glc有12个分支。支链由Ara以1→4或1→5连接,Man的1→3、1→6连接构成,Rha和Glc构成了末端。     

北五味子多糖的分离纯化及抗氧化活性研究

北五味子具有多种药理活性,多糖是其重要的活性成分。通过水提醇沉法得到北五味子中的总多糖(WSP),并通过离子交换层析和分子筛层析对WSP进行分离纯化,得到1个中性糖WSP-N和3个酸性糖级分(WSP-1,WSP-2和WSP-3),对各个级分的单糖组成、相对分子质量等进行分析。通过DPPH清除试验和羟自由基清除试验,研究各级分的抗氧化活性。结果表明,WSP主要由鼠李糖(Rhamnose,Rha)、半乳糖醛酸(Galacturonic acid,Gal A)、半乳糖(Galactose,Gal)、阿拉伯糖(Arabinose,Ara)和葡萄糖(Glucose,Glc)组成,相对分子质量分布广泛。WSP-N主要由Gal、Ara和Glc组成,比例为17.3∶11.9∶62.4。WSP-1,WSP-2和WSP-3主要由不同比例的Rha、Gal A、Gal及少量的Ara组成,其中Gal A的含量分别为43.9%,90.6%和69.3%。WSP对DPPH和羟自由基清除活性明显优于4个子级分,并且清除率随着浓度的升高而增加,具有较好的抗氧化活性。     

大白桩菇多糖的结构鉴定及清除自由基活性

利用水提醇沉法提取大白桩菇粗多糖,用酸性乙醇分级、SepharoseCL-4B以及Sephadex G-100柱层析分离纯化得到大白桩菇多糖（DBZG4-b）。采用高效液相色谱法检测DBZG4-b均一性及相对分子质量。经气相色谱、纸层析、红外光谱、甲基化、气相色谱-质谱、核磁共振方法解析DBZG4-b的结构。结果显示,DBZG4-b为均一性多糖,相对分子质量约为6 864;DBZG4-b为多分支结构多糖,主链由Glc和Gal构成,均以1→6糖苷键连接,Glc在3位上有分支,Gal在4位上有分支;支链由Ara、Glc、Gal构成,其中Ara以1→3连接,Glc以1→3连接,Gal以1→4连接,Ara、Xyl、Rha、Man、Glc、Gal都有一部分构成分子的末端残基。清除·OH与1,1-二苯基-2-三硝基苯肼自由基实验表明,DBZG4-b具有良好的清除自由基能力。     

江水短时浸渍法脱胶亚麻纤维果胶单糖组分的变化

为进一步明确亚麻脱胶过程中果胶单糖组分的变化,利用PMP(1—苯基—3—甲基—5—吡唑啉酮)柱前衍生化高效液相色谱法测定出亚麻纤维果胶由9种单糖组成,其物质的量比为Gal acid∶Ara∶Gal∶Glu∶Rha∶Fuc∶Xyl∶Man∶Glu acid=64.52∶28.23∶25.55∶17.75∶13.41∶7.36∶5.72∶5.18∶5.05。采用江水短时浸渍法脱胶120 h后达到脱胶终点,脱胶过程中单糖含量逐渐降低,但单糖种类变化不大,其中Fuc在脱胶96 h后含量为零。此外,其余各单糖含量变化从大到小依次为Ara、Gal、Glu、Gal acid、Glu acid、Rha、Xyl、Man,损失率分别为85.00%、77.64%、76.67%、66.72%、61.43%、60.44%、48.01%和44.19%。     

桑叶多糖的分离纯化及组成研究

本文对桑叶多糖的提取、分离纯化和单糖的组成进行了研究。桑叶经热水提取乙醇沉淀得多糖粗品，经脱蛋白，乙醇分级沉淀、DEAE-纤维素柱和Sephadex G-100柱层析，纯化得MP11、MP12、Mp13三个多糖组分。经糖腈乙酰化处理后进行气相色谱分析得知MP11由Rha、Ara、Xyl、Man、Glu、Gal组成，其比例为21：16：3：3：1：20；MP12由Rha和Glu组成，其比例为3：1：MP13主要由Rha组成。为桑叶多糖的进一步研究提供了基础。     

洋甘菊多糖的分离纯化、性质结构及抗氧化活性分析

对热回流提取得到的洋甘菊多糖进行了分离纯化,并对得到的多糖的性质结构及抗氧化活性进行分析。经处理后的洋甘菊多糖先后利用DEAE-Sepharose和Sephadex G-100柱色谱分离纯化得到了2种均一多糖(MCP-1-1和MCP-2-1);经测定2种均一多糖总糖含量分别为82.23%、84.09%,糖醛酸含量分别为4.11%、5.38%,蛋白质含量分别为0.58%、1.05%,溶解度分别为98.36%、98.44%,分子质量分别为30902、7244 Da;单糖组成实验结果表明MCP-1-1是由鼠李糖(Rha)、葡萄糖醛酸(GlcA)、半乳糖(Gal)、葡萄糖(Glc)、木糖(Xyl)和阿拉伯糖(Ara)6种单糖组成,MCP-2-1是由GlcA、Gal、Glc、GalA、Xyl和Ara六种单糖组成,2种均一多糖均是不含三螺旋结构的酸性多糖,均含有吡喃环和β-糖苷键,MCP-1-1含有α-糖苷键;2种均一多糖具有良好的热稳定性。体外清除自由基试验结果显示MCP-1-1和MCP-2-1对DPPH自由基和·OH均有清除作用,而且清除能力与均一多糖的质量浓度正相关,MCP-2-1对2种自由基的清除能力明显高于MCP-1-1。研究结果表明,分离纯化得到的洋甘菊多糖可作为天然抗氧化剂,用于食品和化妆品中。     

紫甘薯多糖分离、组分鉴定及抗氧化代谢机理

本实验以紫甘薯为研究对象,通过提取紫甘薯多糖并利用高速逆流色谱对其进行分离纯化,获得一种具有一定抗氧化活性的多糖PSPP03,并对其结构进行理化性质和生物活性分析。结果表明,PSPP03分子质量为29.1 kDa,主要由阿拉伯糖（arabinose,Ara）、甘露糖（mannose,Man）、鼠李糖（rhamnose,Rha）、葡萄糖醛酸（glucuronic acid,GlcA）和葡萄糖（glucose,Glc）组成,物质的量比为16.2∶25.3∶7.1∶8.6∶10.8。甲基化分析结果表明PSPP03的糖苷键构成主要为→1)-Araf-(→3、→3)-Manp-(1→、→3,4)-Manp-(1→、→3,6)-Manp-(1→、→3)-Glcp-(1→、Glcp-(1→和→4)-Rhap-(1→。液相色谱-串联质谱分析结果表明多糖结构中含有芍药素-3-槐糖苷-5-葡萄糖和矢车菊素-3-槐糖苷-5-葡萄糖。细胞氧化实验分析结果表明25、100?μg/mL PSPP03可以极显著降低氧化损伤细胞模型内活性氧、丙二醛和氧化型谷胱甘肽水平（P<0.01）,极显著提高过氧化氢酶、谷胱...     

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.     

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.     

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.     

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.     

Contribution of European research to risk analysis

The European Commission's, Quality of Life Research Programme, Key Action 1—Health, Food & Nutrition is mission-oriented and aims, amongst other things, at providing a healthy, safe and high-quality food supply leading to reinforced consumer confidence in the safety of European food. Its objectives also include the enhancing of the competitiveness of the European food supply. Key Action 1 is currently supporting a number of different types of European collaborative projects in the area of risk analysis. The objectives of these projects range from the development and validation of prevention strategies including the reduction of consumers risks; development and validation of new modelling approaches; harmonization of risk assessment principles, methodologies, and terminology; standardization of methods and systems used for the safety evaluation of transgenic food; providing of tools for the evaluation of human viral contamination of shellfish and quality control; new methodologies for assessing the potential of unintended effects of genetically modified (genetically modified) foods; development of a risk assessment model for Cryptosporidium parvum related to the food and water industries; to the development of a communication platform for genetically modified organism, producers, retailers, regulatory authorities and consumer groups to improve safety assessment procedures, risk management strategies and risk communication; development and validation of new methods for safety testing of transgenic food; evaluation of the safety and efficacy of iron supplementation in pregnant women; evaluation of the potential cancer-preventing activity of pro- and pre-biotic ('synbiotic') combinations in human volunteers. An overview of these projects is presented here.     

低温带皮菜籽粕微粉的不同粒级部分的功能特性

为研究低温带皮菜籽粕微粉的不同粒级部分的功能特性,以经低温脱脂的带皮菜籽粕为原料,经微粉碎后筛分成212~425μm、150~212μm和106~150μm的3个不同粒级的微粉样品,检测这些样品的吸水性、吸油性、乳化性和乳化稳定性、蛋白质体外消化率。结果表明:1 3个不同粒级的微粉样品之间的粗纤维含量存在显著差异,表明三者的结构组成成分有一定差异。23个微粉样品的乳化活性和乳化稳定性随粒度级别的减小而显著增加(P0.01)。33个微粉样品的蛋白质体外消化率随粒度级别的减小而显著增加(P0.01)。4不同粒级带皮菜籽粕微粉样品的吸水性与吸油性受其结构组成物质不同和粒度的双重影响,与粒度的相关性不明显。     

Microbiology of food taints

Fresh and processed foods are often spoilt by the presence of undesirable flavours and odours caused by microbial action. The aim of this paper is to review the current knowledge of microbiologically induced taints that occur in a wide range of foodstuffs, including meats, poultry, fish, crustaceans, milk, dairy products, fruits, vegetables, cereals and cereal products. Examples have been chosen where the compounds responsible for the taint have been identified and sufficient data obtained to demonstrate the involvement of microorganisms. However, in some cases the full identity of the causative organism may not have been elucidated. The types of microorganisms covered by this review include bacteria, fungi, yeasts, actinomycetes and cyanobacteria. Although cyanobacteria do not in general infect foods, their presence in aqueous systems and water supplies can lead to off-flavours in aquatic organisms and processed foodstuffs. Several examples of each of these processes are discussed. Wherever possible, the likely biosynthetic pathway used by the microorganism to produce the offending compound in a foodstuff is indicated.