分光光度法测定发酵液中L-精氨酸含量

建立了定量测定发酵液中L-精氨酸含量的方法。以百里酚的次溴酸钠溶液为显色剂,用正丁醇萃取显色产物,以分光光度计比色测定有机相的吸光度值。测定发酵液中L-精氨酸的最佳条件为:取待测物稀释液5.0mL,依次加入0.03%的百里酚溶液2.0mL,0.7%的次溴酸钠溶液0.5mL,摇匀,30s内加入正丁醇5.0mL,除去水相;向有机相中加入0.4mL无水乙醇,室温放置1min,用分光光度计测定OD480。方法的检出限为2.5μg/mL,摩尔吸光系数ε为1.2×104L/(mol.cm),发酵液样品相对标准偏差为0.89%～1.10%,回收率为97.3%～102.0%。此方法简便、快速、准确可靠,适合用于发酵液中L-精氨酸含量的定量检测。     

发酵液中L-组氨酸的定性定量测定

以组氨酸的茚三酮显色和Pauly特征显色为根据，研究了发酵液中L-组氨酸的定性、定量测定。确立了以Pauly试剂和茚三酮试剂纸层析显色来定性测定组氨酸；茚三酮显色-分光光度法来定量测定发酵液中L-组氨酸，并对测定条件进行了研究。     

发酵液中L-谷氨酰胺的定性定量测定

应用纸层析-分光光度计法对发酵液中L-谷氨酰胺进行了定性分析和定量测定,确立了L-谷氨酰胺定量测定条件.研究结果表明,该法对测定L-谷氨酰胺含量具有较高的准确度和精密度,而且该法操作简单,易于掌握,非常适合在L-谷氨酰胺产生菌筛选中应用.     

发酵液中L-精氨酸定量检测的方法

<正> L-精氨酸是合成蛋白质和肌酸的重要原料,是人和动物体内的半必需氨基酸,在医药和食品工业上具有广泛用途。目前,L-精氨酸的生产很多是通过发酵进行,因而对发酵液中L-精氨酸的测定     

百里酚分光光度法测定发酵液中L-精氨酸含量

目的建立定量检测发酵液中L-精氨酸含量的方法.方法以百里酚的次溴酸钠溶液为显色剂,用分光光度计比色测定.结果百里酚分光光度法检测L-精氨酸的最佳条件为样品稀释液5.0 mL,依次加入0.03%百里酚溶液2.0 mL,0.7%次溴酸钠溶液1.0 mL,摇匀,30 s内加入40%尿素溶液1.0 mL,冰水浴中显色2 min,测定OD470nm.该方法的检出限为2.0 μg/mL,摩尔吸光系数ε为6.8×103L/(mol·cm),回收率98.8%～101.2%,发酵液样品测定的相对标准偏差0.23%～0.59%.结论该方法简便、快速、准确可靠,适合用于发酵液中L-精氨酸含量的定量检测.     

HPLC-ELSD法定量测定发酵液中的L-异亮氨酸

采用高效液相色谱-蒸发光散射检测器(HPLC-ELSD)定量测定发酵液中L-异亮氨酸的含量。结果表明,L-异亮氨酸浓度在0.960~2.880 g/L时,其峰面积(Y)与相应的浓度(X)呈线性关系,线性方程为Y=0.661 5X-0.243 9,相关系数为0.999 7。L-异亮氨酸的平均回收率为99.08%~101.3%,相对标准偏差为0.56%~1.32%。方法的精密度、准确度好,稳定性高,能简便、快速、准确地测定发酵液中L-异亮氨酸的含量。     

发酵液中L-精氨酸定量检测方法的研究

确立了用甲萘酚-双乙酰法定量检测发酵液中L-精氨酸 的最佳条件:40g/LNaOH溶液、80g/L甲萘酚正丙醇溶 液、0.5mL／L双乙酰正丙醇溶液各1mL作为显色液,再加 入1μL适当稀释的发酵液,30℃水浴加热15min后测其 OD540值。对显色反应的稳定性及检测方法的重现性也进 行了研究。     

HPLC-ELSD检测发酵液中L-天冬氨酸含量

采用高效液相色谱-蒸发光散射检测器(HPLC-ELSD)定量测定发酵液中L-天冬氨酸(Asp)的含量,结果表明,L-天冬氨酸浓度在0.8000～3.200 g/L时,其峰面积(Y)与相应的浓度(X)呈线性关系,线性方程为Y=2.8466X-0.138,相关系数R2为0.9995.L-天冬氨酸的平均回收率为99.70%～101.3%.相对标准偏差为0.5601%～2.085%.该方法精密度、准确度好、稳定性高,能简便、快速、准确地测定发酵液中L-天冬氨酸的含量.     

离子排斥色谱法分析米根霉富马酸发酵液中的代谢产物

提出了利用离子排斥色谱法同时分析米根霉富马酸发酵液中主要代谢产物与葡萄糖的方法。在BIO-RAD Aminex HPX-87H色谱柱上,65℃柱温下,以5mmol/L H2SO4溶液作为流动相,流速0.8mL/min,采用示差折光检测器对8种有机酸(草酸、柠檬酸、α-酮戊二酸、L-苹果酸、丁二酸、L-乳酸、富马酸和乙酸)、葡萄糖及乙醇进行了成功的分离,确定了各物质工作曲线的回归方程、线性范围、相关系数和检出限。并应用于米根霉产富马酸发酵液的产品分析,对经预处理后的富马酸发酵液直接进样分离定量,其中的富马酸、-酮戊二酸、葡萄糖、L-乳酸和乙醇完全分离定量,确定了测定发酵液中有机酸、葡萄糖和乙醇的相对标准偏差在0.43%～4.69%,平均回收率在98.41%～104.33%。经多次实验证明,该方法是测定富马酸发酵液中各种主要代谢产物与葡萄糖的准确、有效的定量测定方法。     

由L-精氨酸发酵液制备结晶型精酮合剂

精酮合剂(L-精氨酸-α-酮戊二酸盐,AAKG)是目前国际市场上销量日益增长的一种氨基酸盐类功能制品,通常的产品形式是混合型而非结晶型。实验直接以L-精氨酸(L-Arg)发酵液为原料,通过加入α-酮戊二酸(α-KG)进行络合,制备出结晶型精酮合剂,其主要工艺步骤和控制参数如下:首先对发酵液进行絮凝和过滤,并减压浓缩至L-Arg浓度为1.0 mol/L,再等摩尔加入α-KG进行络合,进一步减压浓缩使AAKG浓度达到1.5mol/L;浓缩液以2℃/h的速率缓慢降温至10℃,恒温结晶24 h,获得粗晶体,并再在同样的条件下进行重结晶。其精酮合剂纯度为99.2%,分子中L-Arg∶α-KG的摩尔比为1∶1.02,产品总收率为62.9%。     

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