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Munro LJ Curioni A Andreoni W Yeretzian C Watzke H 《Journal of agricultural and food chemistry》2003,51(10):3092-3096
Aroma is central to a pleasurable eating/drinking experience but is one of the most labile components of food. Coffee is an outstanding example. Attempts to avoid or control aroma degradation are often frustrated by ignorance of the microscopic mechanisms that are responsible for it. One of the processes most frequently invoked is radical formation, yet the identity of the radicals and their involvement in aroma degradation are poorly understood at the molecular level. Here a step forward in the fundamental understanding of this complex problem is taken by identifying the most relevant radicals and their products using first-principles calculations. Over 100 radicals originating from key aroma compounds found in coffee and other foods have been studied and classified according to an unambiguous criterion: their thermodynamic stability relative to common radical sources. This classification scheme predicts that most aroma molecules are resistant to both peroxidation and attack from phenolic antioxidants but are unstable with respect to radicals such as .OH. Dimers--generated from radical reactions--were also considered, and the most volatile species, which may further contribute to coffee aroma degradation, were focused on. Those--which are very few indeed--that have this potential have been identified. 相似文献
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Dorfner R Ferge T Kettrup A Zimmermann R Yeretzian C 《Journal of agricultural and food chemistry》2003,51(19):5768-5773
The formation of 4-vinylguaiacol, guaiacol, and phenol during coffee roasting was monitored in real-time, using resonance enhanced multiphoton ionization and time-of-flight mass spectrometry. A model is proposed, based on two connected reaction channels. One channel, termed the "low activation energy" channel, consists of ester hydrolysis of 5-FQA followed by decarboxylation of the ferulic acid to form 4-vinylguaiacol, and finally polymerization at the vinyl group to form partly insoluble polymers (coffee melanoidins). The second "high activation energy" channel opens up once the beans have reached higher temperatures. It leads to formation of guaiacol, via oxidation of 4-vinylguaiacol, and subsequently to phenol and other phenolic VOCs. This work aims at developing strategies to modify the composition of coffee flavor compounds based on the time-temperature history during roasting. 相似文献
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Chahan B Zhang S Seo JY Nakamura C Zhang G Bannai H Jian Z Inokuma H Tuchiya K Sato Y Kabeya H Maruyama S Mikami T Xuan X 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2006,68(7):753-755
The prevalence of Babesia (Theileria) equi and B. caballi infections in donkeys in western Xinjiang China was investigated. In total, 93 serum samples were randomly taken from donkeys in the Kashi and Ili areas, and examined for B. equi and B. caballi infections by enzyme-linked immunosorbent assays using recombinant antigens. Of the 93 samples, 9 (9.6%) and 36 (38.7%) samples were positive for B. equi infection and B. caballi infection, respectively. In addition, 2 (2.2%) samples were positive for both B. equi and B. caballi infections. These results indicate that equine babesiosis might be extensively prevalent in donkeys in western Xinjiang. 相似文献
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Chahan B Jian Z Jilintai Miyahara K Tanabe S Xuan X Sato Y Moritomo T Nogami S Mikami T Maruyama S Inokuma H 《Veterinary parasitology》2007,144(1-2):184-187
Tick DNA samples from cattle in Xinjiang Uygur Autonomous Region Area, China, were examined for Rickettsia infection by citrate synthase gene-based PCR and sequencing. Four positive samples were detected from Haemaphysalis danieli and high levels of similarity were found with recently detected 'Candidatus Rickettsia principis.' 相似文献
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[目的]研发一种成熟稳定的新孢子虫病rELISA抗体检测试剂盒.[方法]在新孢子虫病rELISA检测方法建立的基础上,组装检测新孢子虫病的rELISA抗体检测试剂盒,对试剂盒的敏感性、保存期、特异性和重复性进行评价,并与两种商品化试剂盒进行对比试验,应用自制的试剂盒检测来自新疆各地州新孢子虫疑似病例区血清,共1329份.[结果]成功组装了新孢子虫病rELISA抗体检测试剂盒,且该试剂盒敏感性高、保存期长、特异性强、重复性较好.与两种进口商品化诊断试剂盒比较,其符合率均在90;以上.在1 329样品血清中157份是阳性,其平均阳性率为11.8;.[结论]该试剂盒可以取代商品化试剂盒进行新孢子虫病诊断,为新孢子虫病的防治工作提供技术和产品支撑. 相似文献
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为建立特异、敏感、快速的二温式PCR诊断方法,根据牛环形泰勒虫裂殖子表面抗原(tams1)基因,设计了一对特异性引物,扩增出大小为154bp基因片段,经克隆、测序分析,与已知基因序列的相似性为96%。用建立的牛环形泰勒虫病二温式PCR诊断方法,对从新疆牛环形泰勒虫病流行地区采集的50份全血样品进行诊断,阳性率为88%,而血涂片检出的阳性率只有58%。经试验验证,该方法具有特异性高、敏感性强、重复性和稳定性好等优点。表明本试验所建立的二温式PCR诊断方法可用于牛环形泰勒虫病的临床诊断、隐性感染检测和流行病学调查。 相似文献
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Blank I Pascual EC Devaud S Fay LB Stadler RH Yeretzian C Goodman BA 《Journal of agricultural and food chemistry》2002,50(8):2356-2364
The stability of the coffee flavor compound furfuryl mercaptan has been investigated in aqueous solutions under Fenton-type reaction conditions. The impact of hydrogen peroxide, iron, ascorbic acid, and ethylenediaminetetraacetic acid was studied in various combinations of reagents and temperature. Furfuryl mercaptan reacts readily under Fenton-type reaction conditions, leading to up to 90% degradation within 1 h at 37 degrees C. The losses were lower when one or more of the reagents was omitted or the temperature decreased to 22 degrees C. Volatile reaction products identified were mainly dimers of furfuryl mercaptan, difurfuryl disulfide being the major compound. In addition, a large number of nonvolatile compounds was observed with molecular masses in the range of 92-510 Da. The formation of hydroxyl and carbon-centered radicals was indicated by electron paramagnetic resonance spectra using alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone or 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline-N-oxide as spin traps. Whereas *OH was generated by Fenton-type reactions, the C-centered radical is probably a secondary product of the reaction of *OH with various organic molecules, the reaction with furfuryl mercaptan appearing to be the most important. No evidence for S-centered radicals was seen in the spin-trapping experiments, but a sulfur-containing radical was detected when measurements were made at 77 K in the absence of spin traps. 相似文献
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Diagnosis of equine piroplasmosis in Xinjiang province of China by the enzyme-linked immunosorbent assays using recombinant antigens 总被引：1，自引：0，他引：1
Xuan X Chahan B Huang X Yokoyama N Makala LH Igarashi I Fujisaki K Maruyama S Sakai T Mikami T 《Veterinary parasitology》2002,108(2):179-182
The prevalence of equine piroplasmosis in Xinjiang province, China, was examined by enzyme-linked immunosorbent assays (ELISAs). A total of 70 serum samples were taken from horses pastured on three farms in western Xinjiang, and examined for diagnosis of equine Babesia equi (B. equi) infection and B. caballi infection by ELISAs using recombinant equi merozoite antigen 1 (EMA-1) and recombinant P48 antigen, respectively. Of the 70 samples, 28 (40.0%) and 17 (24.3%) samples were positive for B. equi infection and B. caballi infection, respectively. In addition, 11 (15.7%) samples were positive for both B. equi and B. caballi infections. These results indicate that equine piroplasmosis is widespread and therefore a cause for serious concern in western Xinjiang. To our knowledge, this is the first report describing a survey on equine piroplasmosis in Xinjiang province, China. 相似文献