低聚木糖的功能性质与酶法生产

本介绍低聚木糖的组成与食品加工有关的理化性质和生理学特性,确立了玉米芯经稀释预处理后加水蒸煮提取木聚糖,然后再加酶水解提取液的低聚木糖的生产工艺路线。玉米芯红0．1％H2SO4在60℃条件下泡12h ,滤去浸泡液并用水洗至pH6左右,然后进行湿法或干法蒸煮。在优化的条件下,湿法蒸煮和干法蒸煮提取液连渣一起加酶水解的累计可溶性总糖得率可分别达74．0％和67．7％（对原料木聚糖）,水解液低聚木糖有效物含量达到70％以上。     

用于低聚木糖生产的玉米芯木聚糖的蒸煮法提取

通过对几种不同的木聚糖提取方法的比较，确立了酸预处理后加水蒸煮的方法提取低聚木糖生产用木聚糖的工艺路线。首先将玉米芯用质量浓度为１ｇ／Ｌ的Ｈ２ＳＯ４在６０℃下浸泡１２ｈ，滤去浸泡液，然后加水至固液比为１∶１０，在１５０℃蒸煮３０ｍｉｎ．采用此工艺木聚糖的提取得率可达到１７％（按玉米芯计），提取液的还原糖与总糖质量之比小于３３％．该法得到的提取液（和渣一起）用自制的木聚糖酶水解，可获得ｍ（木糖）∶ｍ（木二糖）∶ｍ（木三糖）＝１∶５∶２．７的高纯度低聚木糖产品，产品总糖的得率达到２６．４％（按玉米芯计）。     

稀硫酸预浸辅助蒸汽闪爆法提取玉米芯木聚糖

以木聚糖提取得率和平均聚合度为评价指标,研究了稀硫酸预浸辅助蒸汽闪爆法提取玉米芯木聚糖的工艺,得到最佳工艺条件:预浸用稀硫酸浓度0.1%(w/v),蒸汽压力1.8MPa,维压时间3min。在此条件下木聚糖提取得率达22.33%(对玉米芯重)。同时产生了一部分低聚木糖,其含量为可溶性总糖的39.96%;经内切木聚糖酶初步酶解,所得酶解液的低聚木糖含量达到65.08%(对可溶性总糖)。      

稀硫酸预浸辅助蒸汽闪爆法提取玉米芯木聚糖

以木聚糖提取得率和平均聚合度为评价指标,研究了稀硫酸预浸辅助蒸汽闪爆法提取玉米芯木聚糖的工艺,得到最佳工艺条件:预浸用稀硫酸浓度0.1%(w/v),蒸汽压力1.8MPa,维压时间3min。在此条件下木聚糖提取得率达22.33%(对玉米芯重)。同时产生了一部分低聚木糖,其含量为可溶性总糖的39.96%;经内切木聚糖酶初步酶解,所得酶解液的低聚木糖含量达到65.08%(对可溶性总糖)。     

超声波处理玉米芯制备低聚木糖的条件优化

考察了试验室规模下超声波处理玉米芯提取木聚糖经酶水解制备低聚木糖的影响因素,通过单因素试验和正交试验,优化了提取和水解条件。结果表明:以质量分数5%Na OH溶液为提取剂,超声功率为180 W,超声温度为60℃的条件下提取45 min,木聚糖产率可达到33.18%。所得提取液经脱色,调p H,调木聚糖底物浓度后酶水解制备低聚木糖。最佳酶解条件为:木聚糖底物质量浓度10 mg/m L,加酶量质量分数1.5%(相对于玉米芯干物料),酶水解时间为8 h的条件下,水解液中还原糖的质量浓度达到6.89 mg/m L。     

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。     

玉米芯生产低聚木糖脱色工艺研究

研究了玉米芯生产低聚木糖的脱色工艺。采用由木聚糖酶和纤维素酶组成的复合酶对玉米芯进行水解生产低聚木糖,通过活性炭对低聚木糖提取液脱色工艺进行优化。结果表明,低聚木糖活性炭脱色的最佳工艺条件为:温度为40℃,脱色时间30 min,活性碳添加量20%,可溶性总糖含量11 mg/m L。产品脱色率可达68.93%,还原糖损失率为34.75%,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11.58%。     

超声波辅助碱法制备玉米芯木聚糖

以玉米芯为原料,经高温预处理后,采用超声波辅助碱法提取玉米芯木聚糖,在单因素实验的基础上,通过正交试验对玉米芯木聚糖提取工艺进行优化。结果表明:木聚糖的最佳制备工艺为氢氧化钠浓度7%,料液比1∶25,超声功率250 W,超声时间40 min,超声温度60℃。在此条件下,提取液中以玉米芯计还原糖的含量为64.10 mg/g,可溶性总糖含量为100.14 mg/g,木聚糖得率为9.01%。     

凝胶过滤色谱法研究酶法生产低聚木糖过程中木聚糖分子结构的变化

以玉米芯为原料的低聚木糖生产包括原料的稀酸预处理，蒸煮和酶法水解等过程，本文采用凝胶过滤色谱研究玉米芯木降糖在整个过程中的分子结构的变化。研究结果表明，在选定的稀酸预处理条件下木聚糖不会降解；蒸煮时木聚糖发生随机降解，蒸煮温度越高，降解程度越大，135℃蒸煮30min，大部分木聚糖已有相当程度的降解，但它们的相对分子质量仍然大于1500，该蒸煮条件可满足低聚木糖生产要求；蒸煮液（连渣）加木聚糖酶水解得到的产品的主要成分为木二糖和木三糖等低聚木糖。     

碱法提取木聚糖的酶法水解

在进行碱法提取木聚糖的酶法水解时 ,采用 3 %～ 4%的底物浓度和 2 0U/g底物的加酶量比较合适。在优化的条件下 ,产品的低聚木糖含量达到 79 1% (对总糖 ) ,得率达到 6 6 8%。以去除阿拉伯糖侧链为目的 ,稀酸预水解对随后的碱法提取木聚糖的酶水解作用不大。这表明在木聚糖的酶水解过程中 ,阿拉伯糖侧链与整个木聚糖的水解同步进行。      

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.     

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     

Chinese CTP Market

According to Printing and Printing Equipment Industries Association of China（PEIAC）＇s statistics to the plate manufucturer in China, in 2013, the actual offset plate production has reached 346 million square meters in China. Among them, the CTP production volume was 245 million square meters, up by 11% than that of last year; the total sales of the CTP plate was 239 million square meters, up by 13%.     

Preparatory Work of Print China 2015 is Going Smoothly

正Held at Guangdong Modern International Exhibition Center,Print China 2015 will cover 7exhibition halls,besides the original Hall No.3,4,5,6,7,the newly built F zone of Hall 3 will be used too.The total area will be140,000 square meters.Hall 3:Offset and large printing equipment,package printing equipment,post press