柑橘果胶酯酶的研究

柑橘中含有大量的果胶酯酶（PE）,可分为热稳定性果胶酯酶（TS—PE）与热不稳定性果胶酯酶（TL-PE）,是由几种同工酶组成的。PE会引起果胶的水解,使新鲜果汁特有的浑浊状态丧失,影响柑橘果汁的色泽,美味。可以通过加热处理、高压技术、脉冲电场、PE抑制剂等来钝化柑橘汁中的PE活性。     

柑桔属柠檬类果实果胶酯酶的活性分析

果胶酯酶（PE或PME）能催化果胶脱酯生成低酯果胶和果胶酸,属于一类果胶酶,广泛应用于食品特别是果品加工工业中。以新鲜柠檬为原料,采用NaCl-冷冻离心-盐析的方法提取柠檬果实中的果胶酯酶,pH-stat法对果胶酯酶进行活性分析。研究温度、pH、相对储藏度等因素对柠檬类果实果胶酯酶的活性影响,并探索该酶的最适温度、最适pH值,进而研究该酶的热稳定性;对柠檬果实中果胶含量进行测定。实验表明：58℃,pH=6.90时柠檬中的果胶酯酶的活力最高。     

柑橘皮果胶提取工艺的研究

采用盐酸提取、乙醇沉淀的方法提取柑橘皮中的果胶,通过正交试验研究浸提温度、浸提pH、料液比和浸提时间对柑橘皮果胶提取率的影响。结果表明,柑橘皮果胶提取的最佳工艺条件为:pH 2.0、料液比1∶20(g/mL)、浸提时间90min、浸提温度85℃,柑橘皮果胶的最大提取率为20.12%。     

柑橘皮果胶提取工艺的优化

目的:研究柑橘皮果胶提取的最优工艺.方法:以干燥的柑橘皮为试验原料,采用纤维素酶溶液提取果胶;以果胶提取率为考察指标,在单因素试验的基础上,进行L4(23)正交试验设计,研究了纤维素酶的浓度、浸提时间、浸提温度以及溶液pH值对柑橘皮果胶提取率的影响.结果:纤维素酶溶液的浓度是影响柑橘皮果胶提取率的最主要因素;纤维素酶溶液提取柑橘皮果胶的最佳工艺条件为:纤维素酶溶液浓度为0.5％,浸提时间为45 min,浸提温度为45℃,溶液pH值为5.6,在此条件下,柑橘皮果胶的提取率可达到36.56％.结论:该提取工艺的果胶提取率高,可用于柑橘皮果胶的提取.     

RT-PCR法克隆柑橘皮果胶酯酶基因

试验利用RT-PCR技术将新鲜柑橘皮果胶酯酶基因克隆到pGEM T-Easy载体上,并进行了鉴定和序列测定.结果表明:该基因为克隆成功的果胶酯酶基因,全长1797bp,开放阅读框架长1785bp,共编码594个氨基酸.该序列含有PMEI和Pectinseterase两个保守序列.该序列与Coyadonga R发表的ci...     

黑曲霉果胶酯酶固定化前后酶学性质比较研究

采用明胶加戊二醛包埋法和蛋壳微粒吸附法分别对黑曲霉果胶酯酶进行了固定化,并研究了两种固定化方法制备得到的固定化黑曲霉果胶酯酶的酶学性质.结果表明,通过固定化,黑曲霉果胶酯酶的各项酶学性质指标都得到了改善,明胶固定化果胶酯酶和蛋壳固定化果胶酯酶的酶活回收率分别为46.3%和42.2%,而且与游离果胶酯酶相比,两种固定化酶的最适温度都由40℃上升到45℃,最适pH由4.4下降到4.0和4.2,Km值0.0113%由下降到0.0033%和0.0027%.     

纤维素酶及耐高温淀粉酶提取柑橘皮果胶的研究

为提高柑橘皮果胶提取质量,本研究通过单因素及正交试验研究了纤维素酶与耐高温淀粉酶复合酶法对柑橘皮中果胶提取的影响。复合酶提取柑橘皮果胶的最佳工艺条件为:纤维素酶及耐高温淀粉酶的加量为45 U/g柑橘皮粉,pH为5.0,于55℃下提取3.0 h。该条件下提取率为36.48%。     

柑橘皮中有效成分提取的工艺优化研究

研究以柑橘皮为原料,用乙醇浸取经过预处理的柑橘皮,经石油醚萃取和乙醇精制得油溶性色素和水溶性色素,得出较佳工艺:在室温下,柑橘皮与浸取溶剂比为1:3,浸取时间为4h,油溶性色素的得率为1.21%,水溶性色素的得率为6.45%.并通过正交实验法对果胶提取的最佳条件进行探讨,选用HCl水解,得到果胶的最佳提取工艺条件为:T=90℃, t=2.0h, pH=2.0,选用80%乙醇来沉淀果胶,果胶得率是20.3%.     

苹果果胶酯酶提取及其酶学性质探究

以国光苹果为原料,通过单因素和正交实验考察了Na Cl浓度、p H、提取温度和提取时间对苹果果胶酯酶酶活的影响,确定了苹果果胶酯酶最佳提取工艺参数,并研究了苹果果胶酯酶的酶学性质。结果表明:在Na Cl浓度为2.5mol/L、p H为8.5、提取温度30℃和提取时间为27h时,苹果果胶酯酶的酶活达到0.98μmol/min·m L;该酶反应的最适温度为40℃,热稳定性较差,最适p H为11;金属离子中Ca2+对果胶酯酶有显著的激活作用,Na+、K+和Fe2+也有一定的激活作用,而Ba2+、Mn2+和EDTA对果胶酯酶有抑制作用。     

自制果胶酯酶处理BCTMP白水中DCS物质

用液态发酵法让黑曲孝产果胶酯酶,酶活力为467U/ml,果胶酯酶的最佳PH为4.0,温度50°C.用自制果胶酯酶处理含DCS水,CD值最多降低30%,并使得DCS水料径分布改变,浊度降低,电导率增大.最适加入最为150U.100ml,继续增大酶用量会导致CD值回升.最佳时间为60min,继续延长处理时间,CD值、浊度和电导率变化不大.     

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