培养基优化对两种乳链菌肽效价测定方法的影响

为了提高琼脂扩散法和分光光度法测定乳链菌肽效价的效率,对检验培养基进行了优化,考察使用优化后的培养基对这两种测定乳链菌肽效价方法的影响。以测定结果的相对误差与相对标准偏差为衡量指标,判断使用优化后的培养基是否有利于以上两种检测方法测定乳链菌肽效价的准确度与精密度的提高。结果表明:培养基优化后,分光光度法测定乳链菌肽效价的准确度和精密度得到了提高;琼脂扩散法使用优化培养基测定乳链菌肽效价的结果相对误差较大,且在乳链菌肽浓度较低时无法形成抑菌圈,而使用基本培养基时,琼脂扩散法测定乳链菌肽效价的灵敏度高且相对偏差小,测定结果的准确度较高,故利用琼脂扩散法测定乳链菌肽效价时应选用基本培养基。      

乳链菌肽效价测定方法的研究

对琼脂扩散法测定乳链菌肽效价的条件进行了研究,利用标准曲线的斜率和y轴截距评价测定的精确度和灵敏度。结果表明,当使用检测培养基（一）,溶壁小球菌作为检测指示菌,菌悬液浓度约107ctu／ml,检测培养基琼脂浓度0.75％,琼脂层厚度2mm时,测定结果有较高的精确度、灵敏度;吐温20的添加使精确度略有下降。     

乳链菌肽效价检测技术研究进展

乳链菌肽(Nisin)是由乳酸链球菌(Streptococcus lactis)发酵产生的一种由34个氨基酸组成的多肽类抑菌物质。其作为天然食品防腐剂,广泛应用于乳制品、发酵饮品、肉类制品等食品工业中。多年来已应用了多种方法来检测乳链菌肽的效价。基于乳链菌肽的抑菌性能,最早采用琼脂扩散法检测乳链菌肽效价,之后相继运用了其他多种方法,但是这些方法各有特点。对其进行了综述,以便在科研与实践中进行选择和应用。     

温度对琼脂扩散法测定Nisin效价的影响

4℃预扩散和培养温度是影响琼脂扩散法测定Nisin效价的两个重要因素。4℃预扩散可明显改进Nisin在琼脂中的扩散效果,提高效价测定的精确度。30℃培养时,Nisin效价测定的精确度和灵敏度最高。      

Tween对精炼大豆油氧化稳定性的影

本文采用烘箱法和Rancimat法研究了亲水性乳化剂Tween（如Tween20、Tween60和Tween80）对精炼大豆油氧化稳定性的影响。低温下的烘箱法研究结果表明：对于Tween20,添加0．005％时可以延缓油脂的氧化．添加量增加到0．01％～0．20％时会在一定程度上起到促进氧化的作用;添加Tween60会在一定程度上起到促进氧化的作用：添加Tween80能延缓油脂的氧化,添加量为0．005％时效果最明显。高温下的Rancimat法结果表明：添加0．005％的Tween20具有一定的抗氧化作用,加入0．01％邗．20％Tween20对油脂的氧化稳定性影响不明显。添加Tween60对大豆油的氧化稳定性没有太大影响。添加Tween80能延缓油脂的氧化,加入0．005％Tween80时延缓氧化的效果最好。     

椰子汁饮料的稳定性研究

系统地研究了椰子汁饮料的生产工艺及影响其稳定性的主要因素，得到最佳的工艺条件：椰子肉和水的质量比为1：10，pH控制在6．5左右，加糖量为4．0％，均质条件是在70℃左右保持压力为20～25MPa，杀菌条件是121℃、20min，同时探讨了不同HLB值的混合乳化剂和增稠剂对椰子汁饮料稳定性的影响，结果表明：HLB值在11．27时乳化剂具有良好的效果，Tween60的效果优于其他乳化剂，黄原胶的效果比海藻酸钠要好。通过b9（3^4)正交试验得出稳定剂配方为；0．02％单甘酯、0．08％Span20、0．10％Tween60，0．02％黄原胶、0．02％海藻酸钠。     

低温禽肉制品非冷藏保鲜液配方的研究

以溶菌酶、Nisin（乳链菌肽）、乳酸钠和双乙酸钠为保鲜剂应用于低温禽肉制品保鲜，采用正交试验方法，对配比成分的比例进行优选。结果表明0．05％Nisin＋0.05％溶菌酶＋2％乳酸钠＋1％双乙酸钠的保鲜液配方较优，用此保鲜液处理再结合真空包装能使低温禽肉制品在15℃～20℃条件下保鲜20d。     

缓冲策略在乳酸乳球菌发酵生产乳链菌肽中的应用研究

通过对乳链菌肽生产菌株Lactococcus lactis Z801发酵特性的研究,并使用缓冲策略改善发酵条件,使乳链菌肽单批发酵效价得到大幅度提高。发现用Tris缓冲液配制CM发酵培养基,并添加1.5%的CaCO3,初始pH7.5,30℃,振荡培养可以使乳链菌肽的发酵效价提高近2700IU/mL,而且发现添加CaCO3可以大大延缓发酵后期发酵液效价的快速下降。      

测定发酵液中乳链菌肽效价的微机处理方法

在生物扩散法测量乳链菌肽溶液效价的基础上,提出了用电子表格单元格的计算功能,对乳链菌肽溶液效价对主其抑菌圈直径进行线性回归了分析,快速求出其线性回归方程。     

乳酸发酵型红枣饮料工艺的研究

研究了用红枣进行乳酸发酵，确定了发酵红枣饮料的最佳工艺条件为：预煮和蒸煮料水质量比1：5，预煮10min去苦，蒸煮10min；纯枣浆发酵条件的筛选：乳糖加入量为2％，蔗糖加入量10％，接种量为7％，培养温度41℃，pH值为3．70；稳定剂最佳配比为：黄原胶0．09％，海藻酸钠0.06％，琼脂0．15％；红枣乳酸饮料在压力为25～40MPa，温度为60～70℃下均质处理后，产品组织均匀，口感细腻柔和，稳定性良好。     

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