活性炭-新磷酸钙对玉米芯低聚木糖脱色工艺优化

采用活性炭-新磷酸钙体系对高温蒸煮玉米芯酶法制备的低聚木糖进行脱色工艺研究。经过单因素试验和响应面分析,得出玉米芯低聚木糖脱色最佳工艺条件为:活性炭添加量2.00 g/L、氢氧化钙添加量3.00 g/L,脱色温度49℃,脱色时间31 min,初始pH 4.6。此时,低聚木糖脱色率可达到90.88%,还原糖损失率为5.16%。     

玉米芯低聚木糖脱色工艺研究

采用静态吸附法对比研究了AB-8,HPD-100,D101,DM301,DM130和活性炭对玉米芯低聚木糖的脱色效果,筛选最佳脱色剂并对其脱色工艺进行研究。结果表明,玉米芯低聚木糖脱色最佳工艺条件为选择AB-8为脱色剂,脱色温度为40℃,脱色时间2 h,AB-8添加量为6%,可溶性总糖含量10.6 mg/mL。在此优化条件下,脱色率可达73.65%,还原糖损失率为15.19%,脱色后的低聚木糖溶液经乙醇沉淀后制备低聚木糖,得率为15.7%。     

基于混合离子交换树脂玉米芯低聚木糖脱盐脱色工艺研究

采用混合离子交换树脂对玉米芯低聚木糖提取液脱盐脱色工艺进行优化,并利用薄层层析和高效液相色谱对提取的玉米芯低聚木糖组分进行分析。结果表明,玉米芯低聚木糖混合离子交换树脂脱盐脱色最佳工艺为:D301和001×7离子交换树脂混合比例1:1,反应温度50℃,反应时间120 min,还原糖浓度为0.570 mg/m L,p H5.0,在该条件下低聚木糖溶液的脱盐率为98%,脱色率为76%,还原糖保留率为65%。组分分析表明,玉米芯低聚木糖提取液中主要为木糖、木二糖、木三糖和木四糖,经混合离子交换树脂脱盐脱色后各成分的保留率分别为21.3%、31.4%、5.3%、3.8%。     

低聚木糖制备工艺研究

以玉米芯为研究对象,通过一系列单因素实验、正交试验和方差分析的方法,着重对低聚木糖转化工艺条件、低聚木糖脱色工艺条件和醇沉工艺条件进行了研究,研究结果表明:低聚木糖转化的最佳工艺条件为调整木聚糖溶液浓度为11%,调pH为5.5,加入木聚糖酶500 IU/g,在52℃条件下酶解8 h;低聚木糖脱色的最佳工艺条件为调整可溶性糖的含量为13%,加入35%的活性炭,30℃条件下处理40 min;通过控制不同乙醇浓度沉淀低聚木糖,得出无水乙醇醇沉效果最佳。在上述工艺条件下制备的低聚木糖产品中,XOS2-7含量达到72.5%,XOS2-4含量达到55.6%。     

离子交换树脂对玉米芯低聚木糖脱色脱盐工艺研究

采用阳阴离子交换树脂串联法对玉米芯低聚木糖提取液进行脱色脱盐工艺研究,并利用薄层层析和高效液相色谱对制备的低聚木糖进行组分分析。结果表明,阳离子树脂001×7与阴离子树脂D301串联脱色脱盐效果好,最佳工艺为:温度40℃,时间60 min,阳阴离子树脂比例为1:2,初始还原糖浓度为0.938 mg/m L,p H6.0,在该工艺条件下,脱色率和脱盐率分别为98.8%和68.1%,还原糖保留率为67.3%。组分分析表明,玉米芯低聚木糖提取液中主要为木糖、木二糖、木三糖和木四糖,提取率分别为4.6%、3.7%、0.3%、6.0%,经离子交换树脂脱色脱盐后保留率分别为99.2%、45.5%、6.0%、24.9%。     

低聚木糖分离纯化的研究

利用Freundlich吸附等温方程对活性炭和阴离子交换树脂的色素吸附效能进行了评价,选择活性炭Ly-T-ac和离子交换树脂D-301作为低聚木糖液中色素的吸附剂。通过单因素实验确定了低聚木糖液的活性炭脱色条件为:温度80℃,pH5.0,活性炭用量4%,脱色时间1.5h,活性炭对糖液的脱色率为81.40%。阴离子交换树脂D-301在9%用量,温度40℃脱色2.5h下对糖液的脱色率为40.50%。低聚木糖糖液经过阴阳离子交换树脂脱盐处理后,脱盐率为65.65%。     

蔗渣制备低聚木糖溶液的脱色脱盐工艺及其组分分析

利用活性炭结合阴阳离子交换树脂吸附技术研究甘蔗渣制备低聚木糖溶液的脱色脱盐工艺,并采用高效液相色谱分析精制后的低聚木糖溶液组分。结果表明：活性炭对低聚木糖溶液最佳脱色工艺为活性炭添加量质量分数1%、反应温度60 ℃、吸附时间1 h,在该条件下溶液脱色率为80.25%、还原糖保留率为98.70%。通过对7 种不同型号的树脂进行筛选,确定选用001×7和D301树脂串联、V（001×7）∶V（D301）=2∶1、流速254 mL/h时,离子交换树脂对低聚木糖脱盐效果最佳。经过活性炭和离子交换树脂共同脱色脱盐,低聚木糖溶液的最终脱色率为92.4%、脱盐率为79.2%,溶液接近中性（pH 7.4）。高效液相色谱法分析确定低聚木糖水解得到的单糖主要为木糖,还含有少量的甘露糖和葡萄糖,其中木糖占所有单糖的88.9%;低聚木糖溶液主要为木二糖和木三糖,还含有少量的木糖和木五糖。     

甘蔗叶低聚木糖的分离纯化

研究低聚木糖水解液分别经过酸析脱色和活性炭脱色,旋转蒸发仪浓缩纯化处理,得到纯度较高的低聚木糖产品。通过对酸析和改性活性炭脱色条件优化,得到的优化脱色条件是:酸析脱色pH3.0,脱色温度50℃;活性炭用量是10%(w/v,活性炭/溶液),初始pH值是3.0,脱色温度是80℃,脱色时间是100min,此时的脱色了为55.06%。两种方法结合脱色率是68.96%。用旋转蒸发仪将经过脱色处理的低聚木糖水解液进行浓缩,并辅以乙醇继续浓缩得到浓缩糖浆,其中的低聚木糖含量达到32.08%(w/w,低聚木糖对固形物)。     

玉米芯制备木糖的工艺研究

目的研究玉米芯制备木糖的最佳工艺条件。方法以颗粒状玉米芯为原料,采用酸解法制备木糖,选择不同的酸度、酸解温度、酸解时间和固液比,以木糖提取率确定最佳工艺条件。结果最佳工艺条件为:酸解温度120℃,酸度1%,玉米芯和工艺水的固液比1:10,酸解时间2 h。水解液经活性炭脱色和离子交换后透光率大幅度提高,在420 nm下透光率可达90%以上;电导率大幅度降低,说明去除了糖液的各种离子。结晶后木糖产率较高,8 t玉米芯可产1 t成品木糖。结论采用此工艺条件制备木糖,木糖的产率较高。     

重组木聚糖酶酶解玉米芯制备低聚木糖

研究了蒸煮法及碱提法对玉米芯木聚糖的提取效果,并利用重组木聚糖酶Xyn A对玉米芯低聚木糖的酶解制备条件进行了优化。对木聚糖得率及酶解产物进行了分析,确定碱提法所得玉米芯木聚糖适宜作为酶解底物制备低聚木糖。优化后得到酶解制备玉米芯低聚木糖的工艺条件:底物浓度0.9%,酶解温度49℃,酶解时间4.5 h,还原糖量可达33.9%。另外,对酶解成分进行分析,结果表明酶解碱提玉米芯木聚糖可产生以木二糖及木三糖为主要成分的低聚木糖。     

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.