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排序方式: 共有315条查询结果,搜索用时 31 毫秒
1.
2.
The glycerol region geometry of modeled saturated monoacid triglycerides was altered by bond rotations and minor angle distortions
to convert theoretical α-forms into bent β′- and β-forms. Direct α to β conversion involves lateral disruption of fatty chain
packing to generate side-chain character typical of the β-form. Such disruption, which could contribute to fat bloom, allows
additional molecular movement and shifts in molecular mechanics energy (MME) that may approximate thermal changes observed
by differential scanning calorimetry during α to β transformations. Energy calculations at 100 points throughout each transformation
identified plausible conversion routes. A two-stage conversion, α to either of two stereospecific β′-forms bent at glycerol
followed by subsequent conversion to β, showed less chain movement and more favorable MME than direct α to β conversion. The
preferred path, based on energy profiles of each conversion, involves a β′-D form and rotation of carbonyl to α-carbon bonds
in chain #2 and a side chain (chain #3). 相似文献
3.
Dorota Johansson Björn Bergenståhl 《Journal of the American Oil Chemists' Society》1992,69(8):728-733
The influence of water on the interactions between fat and sugar crystals dispersed in triglyceride (vegetable) oils was qualitatively
estimated from sedimentation and rheological experiments. The experiments were performed both with and without food emulsifiers
(monoglycerides and lecithins) present in the oil. The effects of minor natural oil components (nontriglycerides) on the interactions
and on emulsifier adsorption to the crystals were examined by comparing a commercial refined oil and a chromatographically
purified oil. The results show that water generally increases the adhesion between fat and sugar crystals in oils and also
increases the surface activity of the oil-soluble food emulsifiers. Minor oil components give a small increase in the adhesion
between fat and sugar crystals in oils, but do not influence the adsorption of food emulsifiers in any systematic way. 相似文献
4.
Guan-Chiun?Lee Dong-Lin?Wang Yi-Fang?Ho Jei-Fu?ShawEmail author 《Journal of the American Oil Chemists' Society》2004,81(6):533-536
Lipase from Pseudomonas fluorescens efficiently catalyzed the alcoholysis of various TG in dry alcohols. For TG with short-chain FA, more MG were accumulated.
The yields of MG were affected by the alcohols used. The maximum yields of MG were as follows: 85% for monoacetin in n-butanol, 96% for monobutyrin in ethanol or n-butanol, 50% for monocaprylin in n-butanol, 48% for monolaurin in isopropanol, and 45% for monopalmitin in isopropanol. The MG produced were judged to be 2-MG
by TLC analysis. The presence of organic cosolvent affected the reaction rate of the lipase-catalyzed alcoholysis of TG. For
the alcoholysis of various TG in ethanol and cosolvent (1∶1, vol/vol), the rates had the following orders: (i) for tributyrin,
hexane > toluene > acetone > ethyl acetate > chloroform > acetonitrile > pyridine; (ii) for tricaprylin, hexane > acetone
> toluene > acetonitrile > ethyl acetate > pyridine > chloroform; and (iii) for trialurin, hexane > acetonitrile=acetone >
ethyl acetate > pyridine=chloroform > toluene. 相似文献
5.
Craig A. Dorschel 《Journal of the American Oil Chemists' Society》2002,79(8):749-753
A study of processed peanut oil was undertaken to assess the utility of HPLC combined with tandem MS to obtain data easily
regarding the number of TAG of fats and oils and their FA composition. Mass chromatograms and spectra corresponding to only
TAG of a single M.W. were obtained for the full range of TAG in the sample. Analysis of the mass spectra allowed the identification
of more than 160 TAG in the sample by their FA composition. In addition, it was possible to estimate relative abundances of
the TAG and suggest the position of the FA on glycerol for a limited number of cases. This technique greatly simplifies the
task of assigning FA to coeluting TAG and facilitates identification of TAG present in trace quantities in mixtures, with
possible application in circumstances where such trace TAG could be significant markers. Results are quickly obtained without
extensive sample preparation or prefractionation of the sample. 相似文献
6.
Yuen May Choo Ah Ngan Ma Hawari Yahaya Y. Yamauchi M. Bounoshita M. Saito 《Journal of the American Oil Chemists' Society》1996,73(4):523-525
Successful separation of triglycerides, diglycerides, free fatty acids, carotenes, tocopherol, and tocotrienols from crude
palm oil has been achieved by supercritical fluid chromatography (SFC) with a combination of a C18 and a silica gel column.
The separation was carried out by the programmed extraction elution method. Free fatty acids were separated into five components
by gas-liquid chromatography; tocopherol and tocotrienols were also separated into four components by SFC analysis, and the
pure fractionated carotenes were obtained by preparative SFC. Thus, by using supercritical fluid chromatography, crude palm
oil components can be separated and fractionated, based on differences in their functional groups. 相似文献
7.
酶催化合成高纯度甘油中碳酸单酯 总被引:3,自引:0,他引:3
研究了无溶剂体系中脂肪酶LRI催化合成甘油中碳酸单酯(MG)。得到适宜的反应条件为:反应温度57℃,n(酸)∶n(甘油)=1∶1 1,加酶量100U/g(酸),甘油初始含水量w(H2O)=12%,封闭物系反应4h转敞开物系反应6h。产物中甘油中碳酸单酯质量分数w(MG)=42 20%。将n(酸)∶n(甘油)降低至1∶9,反应时间缩短至4h,粗产物经脱甘油和脱酸处理,可获得高纯度甘油中碳酸单酯。纯化后产品中基本不含游离酸及甘油,其中甘油中碳酸单酯质量分数w(MG)=73 65%。过量加入的甘油全部可以回收利用,其平衡转化率降低不超过2%。 相似文献
8.
Shirom Arie; Melamed Samuel; Rogowski Ori; Shapira Itzhak; Berliner Shlomo 《Canadian Metallurgical Quarterly》2009,14(4):349
The authors investigated the direct and interactive effects of the job demand– control–support (JDC-S) model’s components on subsequent changes in high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and triglycerides (TRI) separately for male and female employees. In contrast to all 14 past studies on these relationships, the authors used a longitudinal design. Study participants (N = 1,137, 66% men) were all apparently healthy employees who underwent a routine health check at 2 points in time (Time 1 and Time 2) about 22 months apart. In these analyses, the authors controlled for the Time 1 level of each criterion and for other confounders. Most of the direct and moderating effects found did not support the predictions of the JDC-S model; this finding is in agreement with the majority of past cross-sectional studies. The authors did not find any evidence supporting the existence of a reverse causation for either of the components of the JDC-S model. The authors suggest that serum lipids may not be a physiological mechanism mediating the effects of the JDC-S model on atherosclerotic diseases. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
9.
Val rie Eychenne Zphirin Mouloungui 《Journal of the American Oil Chemists' Society》2001,78(3):229-234
Thionation using the Lawesson’s reagent (LR) led to quantitative and selective replacement of carbonyl groups (C=O) with thionocarbonyl
groups (C=S). Mixtures of thionotriglycerides were obtained by reaction of 2,4-bis (p-methoxyphenyl)-1,3-dithia-2,4-diphosphetane-2,4-disulfide in suspension with triglycerides (TG). With a molar ratio (LR)/(TG)=3∶2,
there was complete exchange of C=O with C=S in the carboxylic groups of the TG. The yield is over 90%. The two P=S ligands
in the LR confer a double reactivity, producing a high power of thionation. Fourier transform infrared spectroscopy was employed
for quantitative and qualitative characterization of the thionated TG and for monitoring the progress of partial or total
thionation as conditioned by the molar ratios of the starting compounds. Thus, with molar ration LR/TG of 0.108, 0.36, and
0.72, we obtained around 6, 20, and 40% of C=O conversion, respectively. 相似文献
10.
Oxidative stress is an important factor in the occurrence and development of liver disease. Medium-chain fatty acids (MCFAs) have potential antioxidant function, whereas the exact underlying mechanism of MCFA in oxidative injury of hepatocytes remains unclear. In our present study, three different MCFAs, 8-carbon octanoic acid (OA), 10-carbon capric acid (CA), and 12-carbon lauric acid (LA), have been performed to observe their protective action for hepatocyte under the H2O2 challenge. The result showed that MCFA treatment significantly increased the cell viability, T-AOC, and expression of antioxidant-related genes in AML12 cells under oxidative stress condition, and reduced reactive oxygen species (ROS) production. Moreover, MCFA treatment significantly increased the protein expression of Nrf2 and the phosphorylation level of ERK1/2; LA treatment significantly promoted the Nrf2 nuclear translocation. With a further test, the rescue ability of MCFA was blocked by treating with the ERK inhibitor U0126. Overall, our data suggested that MCFA treatment has positive impact on protecting AML12 cells against oxidative stress through ERK1/2/Nrf2 pathway. 相似文献