超声处理对葡萄细胞壁果胶组分的影响

为明确超声处理下葡萄细胞壁中不同果胶组分含量及结构变化，本研究采用不同超声时间和超声功率对葡萄进行处理，通过咔唑硫酸法、PMP柱前衍生化法、高效液相凝胶色谱分析、扫描电子显微镜、傅里叶变换红外光谱分析和圆二色谱分析等手段分析了葡萄细胞壁中果胶组分含量、单糖组成及结构变化。结果表明，新鲜葡萄细胞壁果胶中碱溶性果胶含量最高，为27.41 mg/g AIR，螯合型果胶含量最低，为8.25 mg/g AIR；不同超声处理后总果胶含量呈下降趋势，其中水溶性果胶含量增加，螯合型和碱溶性果胶含量降低。果胶单糖共检测到6种，不同果胶组分单糖组成不同，水溶性果胶中半乳糖和阿拉伯糖含量较高，螯合型果胶中葡萄糖醛酸含量最多，而碱溶性果胶中含量最高的为鼠李糖；超声处理后果胶组分单糖组成不变，但含量均发生降低；超声作用未改变果胶主链结构，但其线性结构和支链程度均发生变化。随着超声处理时间和功率的增加，不同果胶的分子量整体均呈下降趋势，并且在微观结构上呈现更加松散形态。此外，超声作用对果胶组分特征官能团影响较小，但对螯合型果胶和碱溶性果胶分子的结构和链构象产生作用，使其最大响应值发生移动，并且超声功率作用影响更大...     

原子力显微镜表征采后果蔬结构特性的研究进展

目的:系统介绍原子力显微镜的原理及其在采后果蔬结构特性研究中的优点.综述原子力显微镜在果蔬采后表皮微观结构、多糖大分子结构及其相互作用等方面的应用;结果:利用原子力显微镜的粗糙度分析可表征贮藏中果蔬表皮水分蒸发及溶液涂抹对表皮粗糙度的影响;通过定性分析多糖大分子链纳米结构,得到果蔬大分子的分支及聚合特征;通过提取定量链特征参数可以解释贮藏中果胶等大分子纳米层次的降解途径和过程;通过操纵多糖大分子可以模拟采后果蔬中生物大分子的相互作用;结论:原子力显微镜作为纳米尺度的表征工具,通过研究果蔬纳米结构与功能的关系,对揭示果蔬的抗氧化、抗衰老等生理功能有重要意义.     

两种不同质地的莲藕碱溶性果胶组分热降解规律及流变学差异

选择两种不同质地的莲藕作为材料，研究其碱溶性果胶（sodium carbonate-soluble pectin fraction，NSF）的热降解差异及其与流变的关系。对碳酸钠提取的NSF进行不同温度处理，通过一级结构和纳米微观结构观察和分析发现，沔城藕（粉藕）的NSF热降解程度大于芦林湖藕（脆藕）；芦林湖藕NSF链呈星型状（长支链）而沔城藕NSF链大多呈短直链，两者经加热后均出现链长变短、链高降低、分支度减小的现象；流变学结果表明两种NSF的黏稠度经热处理后均明显降低，沔城藕的NSF假塑性略有增加而芦林湖藕NSF假塑性减小。结合结构分析与流变学结果分析得到果胶链的长度、高度与黏稠度呈正相关；分支度和不同长度的链长所占百分比（分子质量分布）是导致其假塑性不同的重要原因。因此，NSF的结构与流变学特性密切相关，同时也说明NSF的热降解差异与两种藕质地差异存在关联。本研究为NSF的热降解与果蔬质构（加工、成熟度）之间的关系提供了一定理论依据。     

苹果梨果实生育期果胶物质的研究

以开发利用苹果梨资源及果实质地的研究为目的,测定了苹果梨生育期果实中细胞壁物质(AIS)以及不同溶解性果胶的舍量.结果表明,随着果实成熟,AIS呈先上升后降低的趋势.果皮和果肉AIS中及鲜果果皮中果胶总含量均在果实膨大期含量较高,成熟后期呈下降的趋势,而鲜果果肉中果胶总含量在盛花后第50d含量较高,随后其含量下降,且其含量均低于果皮中的含量.幼果中以碱溶性果胶含量最多,为果胶的主要成分,成熟果中则以酸溶性果胶含量较多,碱溶性果胶含量次之;水溶性果胶和盐溶性果胶在整个生育期中所占比例较少.     

胡椒固态发酵脱皮过程中果胶的降解

采用红外光谱、离子色谱和高效液相色谱法分析固态发酵过程中胡椒果皮果胶组分结构、含量及其变化。结果显示:胡椒果皮中水溶性果胶、酸溶性果胶为高酯化度果胶,螯合性果胶为低酯化度果胶;水溶性果胶在发酵前36h含量上升,而后下降,酸溶性果胶和螯合性果胶在预处理催熟时含量上升,在发酵过程中含量下降。固态发酵24~48h为果胶主链半乳糖醛酸快速降解期、12~24h为支链阿拉伯糖快速降解期,12~36h为半乳糖快速降解期。发酵48~60h,果胶半乳糖、阿拉伯糖等侧链几乎完全降解。这提示发酵过程中,富含半乳糖醛酸的果胶主链断裂及支链中性糖的降解是胡椒果皮降解的主要原因。     

膳食纤维结构与功能的原子力显微镜研究

膳食纤维的功能是近年来研究的热点,而功能与其结构是密切相关的。基于此,文章主要回顾了原子力显微镜这种新型的研究手段在膳食纤维结构及其功能研究中的应用情况,并详细介绍了原子力显微镜在纤维素、木质素、果胶、树胶等膳食纤维结构研究中的一些初步成果。     

高静压对黄桃质构相关组分模拟体系的影响

以黄桃质构相关组分(细胞壁物质)为模拟体系,探究了高静压处理、热处理以及贮藏过程对细胞壁物质持水性及其果胶各组分和纤维素含量变化的影响。结果表明:与热处理相比,高静压处理对细胞壁物质的持水性、果胶各组分含量和纤维素含量均无显著影响。与常温贮藏相比,低温贮藏对高静压处理及热处理的细胞壁物质的持水性、各果胶组分含量和纤维素含量无显著影响。相关性分析显示:碱溶性果胶与水溶性果胶之间,碱溶性果胶、水溶性果胶与持水性之间相关性较高。     

猕猴桃品种对猕猴桃脆片品质影响的评价

目的:以6个品种的猕猴桃为原料,筛选出最适合加工成脆片的品种。方法:采用真空冷冻干燥的方法制备猕猴桃脆片,测定猕猴桃脆片的得率、脆片中水溶性果胶含量、酸溶性果胶含量、可溶性糖含量、总酸含量、糖酸比、抗坏血酸含量及脆片的硬度和脆度等9个指标,并对猕猴桃脆片进行感官评价。结果:不同品种猕猴桃脆片的得率、营养物质含量和感官指标不同。其中金艳猕猴桃脆片的得率、水溶性果胶含量、可溶性糖含量和硬度较高,总酸含量和脆度较低;金梅猕猴桃脆片的得率、水溶性果胶含量、可溶性糖含量和抗坏血酸含量较高,总酸含量、硬度和脆度较低;金圆猕猴桃脆片的水溶性果胶、酸溶性果胶、结合果胶、可溶性糖、总酸和抗坏血酸含量较高,脆片的硬度和脆度较低;金桃猕猴桃脆片的得率、糖酸比、抗坏血酸等含量及脆片的硬度和脆度较高,脆片的水溶性果胶和总酸含量较低;翠玉猕猴桃脆片的得率、糖酸比和脆度较高,脆片的酸溶性果胶含量、结合态果胶含量、可溶性糖含量、总酸含量和脆片的硬度较低;东红猕猴桃脆片的得率、酸溶性果胶含量、结合态果胶含量、可溶性糖含量、糖酸比和脆片的硬度较高,脆片中水溶性果胶含量、总酸含量和脆片的脆度较低。结论:品种对猕猴桃脆片的得...     

烟草根系分泌物的GC-MS检测

采用水培试验研究对连作障碍有重大影响的烟草根系分泌物中的化感物质,利用GC-MS检测出了K326和NC89两个烤烟品种移栽后40天根系分泌物中的酸溶性、碱溶性和中溶性组分种类,结果表明,两个烤烟品种共有的根系分泌物中可能是化感物质的种类包括有机酸类、酰胺类、酯类以及甘油和烟碱。     

不同品种芡实种仁蛋白质亚基组成及氨基酸分析

本实验选择3个不同品种、2种不同成熟度的5个芡实种仁样品,通过SDS-PAGE法及氨基酸分析仪法对其蛋白质亚基结构和氨基酸组成进行了初步分析。结果表明,刺芡(成熟)种仁蛋白质含量显著高于苏芡(成熟)(p≤0.05),且刺芡(成熟)种仁蛋白质中必需氨基酸、甜味和鲜味氨基酸含量也高于苏芡(成熟),说明刺芡在营养和口感上要优于苏芡。SDS-PAGE的分析结果显示,芡种仁总蛋白中分离出约20条谱带,相对分子质量在16.24~82.04 k Da之间。其中分子量35.9 k Da左右基含量最高,是芡实总蛋白中最主要亚基。芡实蛋白质中的水溶性蛋白含量很少,且不同成熟度样品间差异很大,苏芡(嫩)和淮芡(嫩)中均未检出水溶性蛋白。品种间醇溶性蛋白质亚基组成差异较大,碱溶性蛋白质亚基及分子量分布品种间和成熟度间差异不大。     

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.     

Detection of adulteration of locust bean gum with guar gum by capillary electrophoresis and polarized light microscopy

Capillary electrophoresis (CE) and polarized light microscopy (PLM) were utilized in the detection of the adulteration of locust bean gum with guar gum. For CE analyses, standards of locust bean and guar gums were extracted with 30% CH₃CN, removing the residual proteins from the gum matrix. A 8.75 mM NaH₂PO₄-20.6 mM Na₂B₄O₇ buffer, pH 9, was used to separate these proteins and to identify marker proteins that were present in the guar gum. These markers did not co-migrate with components in the extracts of mechanically processed locust bean gum, and are used as indicators of adulteration. Using PLM with toluidine blue and iodine staining techniques, unadulterated locust bean gum samples were distinguished from mixed samples through the differential staining of components in locust bean versus guar and tara gums. These experiments in the use of CE and PLM provide orthogonal and complementary methods for the verification of 'true' positives and the elimination of 'false' positives.