南极磷虾自溶前后氨基酸和胰蛋白酶降解产物的变化

南极磷虾富含内源自溶酶,死后易快速自溶,限制了其加工利用。为研究南极磷虾自溶特性,测定了不同条件下南极磷虾自溶酶的最适温度和pH值,然后在最适自溶条件下研究了南极磷虾自溶3 h前后的氨基酸态氮含量和组成变化,并对南极磷虾自溶前后的胰蛋白酶降解产物进行了分析。结果表明：南极磷虾自溶酶最适温度为55 ℃,最适pH值为7.5,在此条件下南极磷虾自溶后氨基酸态氮质量浓度升高;甘氨酸和脯氨酸为南极磷虾的主要游离氨基酸,其次为谷氨酸和丙氨酸,南极磷虾自溶后鲜味氨基酸如谷氨酸、甘氨酸、丙氨酸质量分数降低,而苦味氨基酸如亮氨酸、异亮氨酸、酪氨酸和苯丙氨酸质量分数升高;南极磷虾自溶后胰蛋白酶降解产物分子质量分布向小分子质量范围偏移。本实验为进一步研究南极磷虾自溶特性提供了理论依据。     

南极磷虾自溶酶解工艺的研究

对南极磷虾的自溶酶解工艺进行了研究。采用了单因素和正交实验L16(54)确定了南极磷虾的最佳自溶酶解条件。正交实验结果表明,自溶酶解时间是影响氨基酸态氮质量浓度与水解度得率的第一影响因素,pH值是次要因素,反应温度和钙离子浓度对水解影响较小,紫外线的照射时间对自溶酶解液的影响最小。当自溶时间为180min,温度为50℃,pH为7.0,紫外线照射时间为20min,Ca2+离子浓度为0.28mol/L时,自溶酶解液中氨基酸态氮的质量浓度最高,为0.875g/L,其自溶酶解液的水解度为36.18%。     

南极磷虾蛋白酶分离纯化及部分性质研究

对在南极磷虾自溶过程中起主要作用的蛋白酶的分离纯化条件和主要生化性质进行了研究。经过30%～70%硫酸铵分级沉淀,DEAE-Sepharose Fast Flow阴离子交换层析,Sephacryl S-200 HR凝胶层析后得到电泳纯的蛋白酶,该酶纯化倍数为12.59,产率为43%,分子质量约为28 ku;最适pH和最适温度为pH 8.0和50℃;该酶pH稳定范围为pH 7.0～9.5,并在45℃以下较稳定;苯甲基磺酰氟(PMSF)、大豆胰蛋白酶抑制剂(SBTI)、对甲苯磺酰基赖氨酸氯甲基酮(TLCK)对该酶活性有较强的抑制作用。     

果胶酶酶学性质研究

为了充分研究果胶酶的作用,对果胶酶的最适作用pH值、pH值稳定范围、最适反应温度、温度稳定性和金属离子对酶稳定性的影响等进行了研究。结果表明:果胶酶的pH稳定范围为3.0~6.0,最适作用pH为3.5~5.5,在60℃下保温酶活下降较快,最适温度为45~50℃,铁、钙、锌和锡离子对酶活性有抑制作用。     

南极磷虾自溶工艺优化及其自溶产物鲜味评价研究

本研究以南极磷虾为原料,通过感官评定结合自溶产物得率对磷虾的自溶实验初步评定影响因素,利用正交实验优化并确定南极磷虾自溶工艺的最佳参数;并将优化后的南极磷虾自溶产物通过三级膜分离系统,得到不同分子量(＞10.0kDa,3.0～10.0kDa和＜3.0kDa)的组分,并对其鲜味物质进行评价研究.研究结果显示,南极磷虾最优...     

GS0202菌产人参皂苷糖苷酶的酶性质研究

对Arthrobacter chlorophenolicus GS0202菌产人参皂苷糖苷酶进行分离纯化并对其性质进行了研究。结果表明,电泳纯人参皂苷糖苷酶的分子质量约为66ku,最适反应pH值为5.0,最适温度为40℃,在pH3.0～7.0,20～60℃酶活力相对稳定。K+、Na+、Zn2+对酶活性影响很小;Ca2+、Mg2+、Cu2+对酶活性有明显的抑制作用。Km值为4.392mmol/L,Vmax值为0.1275mmol/(h.L)。     

纳豆激酶与豆豉纤溶酶酶学性质比较研究

研究对纳豆激酶和豆豉纤溶酶的酶学性质进行了分析和比较,结果发现,二者最适pH值范围和温度基本一致,分别为pH7.0~9.0、50℃;纤溶酶活性在60℃以上迅速下降;纳豆激酶在pH6.0~10.0、豆豉纤溶酶在pH7.4~12.0时稳定性好;Mg2+对2种酶均有激活作用,Mn2+、Fe2+、Fe3+、Zn2+有不同程度的抑制作用,Cu2+的对纳豆激酶的有显著抑制作用。     

浓香型大曲糖化酶特性研究

大曲作为大曲酒生产的糖化剂、发酵剂,含有多种微生物及其产生的多种酶类。研究表明,大曲糖化酶的最适温度为50℃,最适pH值为6.0;低浓度(0～2 mg/L)的Cu2+对大曲糖化酶有激活作用,高浓度(2～12 mg/L)的Cu2+对糖化酶有抑制作用。     

淫羊藿苷糖苷酶的纯化及其酶学性质的研究

对由菌株Absidiasp.E9r在发酵培养中产生的淫羊藿苷糖苷酶进行了分离纯化并对其酶性质进行了研究。结果表明,该酶的分子质量约为65ku,酶反应的最适温度和pH值分别为50℃和4.0,在20～60℃,pH3.0～6.0条件下稳定性较好;金属离子Na+、K+、Mg2+、Zn2+、Ca2+对酶反应的影响不大,而Fe3+、Cu2+对其有很明显的抑制作用;酶反应动力学研究,Vmax=3.012mmol/(L.h),km=58.59mmol/L。     

皱胃酶酶学性质的研究

研究了皱胃酶的酶学性质。皱胃酶的最适作用温度和最适pH值分别为42℃和6.0。在45℃以下和pH4.5～7.0范围内,酶活保持稳定。Ca2+、Na+、Fe3+对皱胃酶的凝乳有明显的促进作用,Mg2+、Cu2+、Ba2+对凝乳有抑制作用。并研究了底物浓度对酶反应的影响。     

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