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核磁共振技术在脐橙保藏和质量评估中的应用 总被引:2,自引:0,他引:2
采用低场核磁共振技术研究脐橙储藏过程中水分的状态、变化以及水分的迁移.利用Carr-Purcell-Mei-boom-Gill(CPMG)序列采集样品的核磁共振受激回波信号,采用多重指数衰减模型对收集的信号数据进行分析并计算组织中不同水分自旋-自旋弛豫时间.探讨脐橙在储藏过程中品质变化与核磁共振弛豫参数变化的相关性.发现在脐橙的后成熟期、稳定期和腐烂期,对应的自旋-自旋弛豫时间变化呈现一个上升-稳定-急速下降的过程,且在脐橙腐烂前出现了一个自旋-自旋驰豫时间急剧下降的过程.该方法可以作为脐橙质量评估的有效手段,对于脐橙的质量评估和保藏方法的评估等具有指导意义. 相似文献
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核磁共振研究蔗糖对面团中分子流动性的影响 总被引:9,自引:0,他引:9
利用脉冲梯度场核磁共振技术(PFG-NMR)研究蔗糖对面团自旋-自旋弛豫特性的影响。分子的自旋-自旋弛豫特性与分子的流动性呈正相关。采用CPMG脉冲序列检测面团中质子的自旋-自旋弛豫时间(T2)。在面团中流动性不同的水分,表现出不同的弛豫时间。实验结果表明,蔗糖的亲水性能够显著改变面团的自旋-自旋弛豫时间。通过磁共振图像可以发现蔗糖能够明显促进面团中质子的均匀分布,增强其流动性。当水分含量一定时,面团的自旋-自旋弛豫时间随蔗糖含量的增加而增加。 相似文献
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南酸枣糕烘干过程中水分的迁移和分布 总被引:1,自引:0,他引:1
利用核磁共振及其成像技术,探究南酸枣糕在烘干过程中水分含量、迁移和分布情况。通过分析南酸枣糕烘干过程中核磁共振的自由衰减弛豫时间、自旋-自旋弛豫时间和核磁共振成像图发现:南酸枣糕的水分含量与体系的质子密度高度线性相关,其相关系数达到0.990 6。因此,可以通过建立水分含量与核磁共振质子密度的标准曲线实现南酸枣糕水分含量的核磁共振定量测定;在烘干过程中,随着时间的延长,南酸枣糕中的束缚水的流动性(T21)呈降低的趋势,自由水的流动性(T22)呈先增加后降低的趋势,核磁共振成像图逐渐变暗;从成像图也可直观地看出,南酸枣糕内部弛豫信号比外部强,证实南酸枣糕干燥是一个不均匀的干燥过程。 相似文献
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利用低场强核磁共振技术研究热烫温度对纤丝干酪水分状态的影响。通过考察不同热烫温度纤丝干酪贮藏1~10d可榨乳清质量分数,探讨热烫温度对纤丝干酪持水力的影响。利用低场核磁共振仪测定不同热烫温度制作的纤丝干酪贮藏1~10d自旋-自旋弛豫时间T21、T22以及质子强度A1、A2,探讨热烫温度对纤丝干酪水分状态以及分布的影响。结果表明,低热烫温度,纤丝干酪持水力高,结合水、自由水自由度增幅大,同时在纤丝干酪贮藏过程中内部水分发生了迁移,由相对自由态向结合态转移,热烫温度越低水分迁移量越大。 相似文献
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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. 相似文献
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John Gilbert Catherine Simoneau David Cote Achim Boenke 《Food Additives & Contaminants》2000,17(10):889-893
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. 相似文献
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Sophie Guillot Laurence Peytavi Sylvie Bureau Renaud Boulanger Jean-Paul Lepoutre Jean Crouzet Sabine Schorr-Galindo 《Food chemistry》2006
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. 相似文献
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Jesus Simal-Gandara Miguel Sarria-Vidal Arjen Koorevaar Rinus Rijk 《Food Additives & Contaminants》2000,17(8):703-711
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. 相似文献
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M. S. Garcí a-Falc n J. Simal-G ndara S. T. Carril-Gonz lez-Barros 《Food Additives & Contaminants》2000,17(12):957-964
A simple, rapid and inexpensive method has been developed for the determination of benzo[a 相似文献
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H. J. Van Den Top A. Boenke P. A. Burdaspal J. Bustos H. P. Van Egmond T. Legarda A. Mesego A. Mourino W. E. Paulsch C. Salgado 《Food Additives & Contaminants》2001,18(9):810-824
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. 相似文献
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《肉类研究》2014,(2)
<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 相似文献
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《印刷工业》2014,(11):95-95
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%. 相似文献
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《印刷工业》2014,(8):103-103
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 相似文献