茎用芥菜芥子苷酶的特性研究

以黑芥子苷为底物,用葡萄糖测定试剂盒法对茎用芥菜芥子苷酶的特性进行了研究。结果表明,茎用芥菜芥子苷酶的Km为5.22mmol/L,Vmax为0.036mmol/(L·min),其最适反应温度为50℃,最适pH为8.0。抗坏血酸具有激活芥子苷酶的作用,在抗坏血酸浓度为10mmol/L时,酶活力最大。NaCl对该酶有抑制作用,10%NaCl可完全抑制该酶的活性。Al3+、Ca2+、Mg2+、Fe3+对芥子苷酶的影响作用因离子类型不同而异。     

雪菜中芥子苷酶解特性的研究

借助于硫脲紫外分光光度法，对雪菜中的芥子苷的酶解性质进行了研究。经检测，实验用雪菜中芥子苷含量为０．０７％。单因素实验显示，芥子酶的最适ｐＨ６．０～７．０，最适温度７０℃，Ｖｃ对芥子酶有明显的激活作用，而０．５％ＮａＣｌ对芥子酶有显著的抑制作用。正交试验表明，ｐＨ是影响芥子酶活的高度显著性因素，ＮａＣｌ浓度为显著性因素。ＲＳＡ优化试验得出，在室温２０℃下２０％雪菜汁中芥子苷酶解的最佳条件为：ｐＨ６．５６，ＮａＣｌ浓度３．４７％，冷冻干燥芥子酶粗酶粉添加量５．３７ｍｇ（５ｍｌ２０％雪菜汁中），反应１ｈ，最大酶活可达７．６７ｕ。研究结果可供腌制雪菜加工参考使用。     

“鸡皮糙”山药过氧化物酶的酶学特性

对"鸡皮糙"山药中过氧化物酶(POD)酶学特性进行了较为系统的研究。结果表明,"鸡皮糙"山药过氧化物酶的最适pH为4.0,最适温度为35℃,在60℃以下有良好的稳定性;该酶与不同底物结合能力的强弱依次为:绿原酸>愈创木酚>焦性没食子酸>邻苯二酚>没食子酸;Ca2+、Fe2+、Ba2+、Mg2+对该酶有激活作用,K+、Mn2+、Na+对该酶有抑制作用;抗坏血酸、L-半胱氨酸、植酸、草酸、柠檬酸、EDTA-2Na、NaHSO3等褐变抑制剂对酶活力均有不同程度的抑制作用,其中抗坏血酸和L-半胱氨酸抑制效果最好。     

红萝卜中芥子苷酶提取工艺的研究

该研究以红萝卜为原料，用硫酸铵沉淀法提取芥子苷酶，使用考马斯亮蓝法和双缩脲法对粗提物进行了蛋白质定性分析。以提取率为指标，考察液料比、浸提时间、缓冲溶液pH 3个因素对提取率的影响，根据单因素实验结果，进行正交实验，得到最佳提取条件为液料比3(mL/g),浸提时间3 h,缓冲溶液pH 7.0。在此条件下，芥子苷酶粗提物提取率为5.74%,采用DNS法测定酶活，结果显示酶活为96 U。此研究结果能为红萝卜中芥子苷酶的后续研究提供实验基础，为红萝卜的开发和利用提供科学依据。     

茎用芥菜芥子苷酶的分离纯化及组成研究

以茎用芥菜为原料,采用磷酸缓冲液浸提、（NH4）2SO4盐析、DEAE-52和Sephadex G-100色谱对其中的芥子苷酶予以分离纯化,并就该酶的分子特性进行了研究。通过DEAE-52和Sephadex G-100色谱纯化后,回收具有芥子苷水解活性的蛋白质峰。该芥子苷酶的分子质量为105000（凝胶法）;紫外最大吸收峰位于277.3nm;每摩尔酶分子有1.34mol自由巯基;组成酶的氨基酸中,Leu和Gly含量较高,Cys和Lys含量较低。     

一种来源于青霉的β-半乳糖苷酶酶学性质研究

从土壤里筛选到20株产β-半乳糖苷酶的菌株,其中β-半乳糖苷酶活力最高的是菌株L7,通过形态学观察和18SrDNA序列分析,得出该菌株为斜卧青霉;并研究了其β-半乳糖苷酶的酶学性质。结果表明:β-半乳糖苷酶最适作用温度为60℃,最适pH为6.0,在60℃以下和pH3.0 7.0有较高的稳定性;Mg2+、Mn2+对β-半乳糖苷酶活性有显著的激活作用,Cu2+、Fe2+、和Zn+对酶活有较强的抑制作用;以ONPG为底物采用双倒数做图法测得Km为6.25mmol/L;经过聚丙烯酰胺凝胶电泳鉴定,该酶蛋白的分子量约为110kDa。     

黑曲霉TC-01产柚苷酶分离纯化及其降解内毒素研究初探

[目的]对黑曲霉TC-01产柚苷酶进行分离纯化及酶学性质研究,并对柚苷酶降解内毒素进行初步研究。[方法]黑曲霉TC-01发酵优化后的酶液经硫酸铵分级盐析、透析浓缩、DEAE Bio-Sep FF离子交换层析等分离纯化,考察酶学性质,初步研究柚苷酶对内毒素的降解作用。[结果]柚苷酶纯化后,比活力6429.3u/mg,纯化倍数31.1倍。酶学性质研究结果表明TC-01产柚苷酶最适pH4,最适温度60℃,考察金属离子对酶活影响,1~10mM Ca~(2+)、Mg~(2+)对柚苷酶酶活有促进作用,Zn~(2+)、Fe~(2+)、Fe~(3+)、Cu~(2+)对柚苷酶的酶活有抑制作用,Fe~(2+)抑制作用最为强烈。柚苷酶对内毒素具有降解作用,柚苷酶与内毒素反应1h,内毒素降解率达到79.9%。[结论]研究为柚苷酶的工业化生产提供理论依据,同时拓宽了柚苷酶的应用范围,为进一步研究柚苷酶降解内毒素提供了基础数据,具有重要的科学意义和应用价值。     

一株产高活性多酚氧化酶菌株筛选鉴定及其酶学性质

采用变色圈法从土壤样品中分离筛选产多酚氧化酶的菌株,对其进行形态学观察、分子生物学鉴定,并对其所产多酚氧化酶的酶学性质进行研究。结果表明,筛选得到1株产多酚氧化酶活性较高的菌株,命名为ZL-2,其被鉴定为竹黄菌属（Shiraia sp.）。菌株ZL-2发酵8 d产多酚氧化酶酶活最高,达到521 U/mL。菌株ZL-2产多酚氧化酶最适底物为邻苯二酚,其最适pH值为6、最适温度为30 ℃;酶活在温度20～40 ℃及pH 3～6范围内稳定。金属离子Cu2+、Mg2+、Mn2+、Fe3+、Zn2+对多酚氧化酶都有激活作用,其中Cu2+激活作用最强;Ca2+、Al3+对酶活有一定抑制作用;L-抗坏血酸和亚硫酸氢钠对该酶抑制作用较强。     

α-半乳糖苷酶的液体发酵条件和酶学性质研究

研究了臭曲霉ZU-G1液体发酵产α-半乳糖苷酶的最佳生产条件及其酶学性质.试验结果表明,最适发酵条件为温度28℃.转速200 r/min,装液量30 mL(250 mL三角瓶),接种量6.6%,种子培养18 h后接种,发酵144 h后α-乳糖苷酶酶活达到最大值.在此发酵条件下α-半乳糖苷酶最适pH 5.0,于28℃放王7 h,在pH 3.5～6.0内稳定性较好;该酶的最适温度为60℃,在50℃以下存放稳定性较好.Ag 可强烈抑制该酶的活性,Ca2 、Mg2 、Mn2 和Zn2 的激活效果随浓度而变.1mmol/L甘露醇、抗坏血酸和2mmol/L蜜二糖对酶的热稳定性保护效果好.     

八角莲多酚氧化酶的酶学性质

以邻苯二酚为底物,研究八角莲多酚氧化酶（polyphenol oxidase,PPO）粗提液的酶学特性。结果表明,底物邻苯二酚最适浓度为1.0 mol/L,八角莲PPO的最适pH值为7.0,最适温度为30 ℃,90 ℃高温处理10 min,八角莲PPO酶活力仅剩11.92%。PPO催化的酶促褐变反应符合米氏动力学方程,相应动力学参数Km和vmax分别为0.230 7 mol/L和769.23 U/min。抗坏血酸、甘氨酸、乙二胺四乙酸、柠檬酸对酶活性具有抑制作用,十二烷基硫酸钠表现出激活作用,亚硫酸氢钠对酶活性的抑制作用强于硫代硫酸钠,Al3+和Cu2+对酶活性具有一定的激活作用,Ca2+对酶活性有一定的抑制作用,Mg2+、Fe2+和Fe3+对酶活性影响不显著。     

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