• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文会议>American Oil Chemists' Society Conference on Crystallization and Solidification Properties of Lipids 2000 Toronto, Canada >Simultaneous Examination of Structural and Thermal Behaviors of Fats by Coupled X-ray Diffraction and Differential Scanning Calorimetry Techniques: Application to Cocoa Butter Polymorphism
【24h】

Simultaneous Examination of Structural and Thermal Behaviors of Fats by Coupled X-ray Diffraction and Differential Scanning Calorimetry Techniques: Application to Cocoa Butter Polymorphism

机译：X射线衍射和差示扫描量热技术相结合的脂肪结构和热行为的同时检查：在可可脂多态性中的应用

获取原文
获取原文并翻译 | 示例
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The presence of one or several long chains, the different packings of which lead to a variety of polymorphic forms, renders the thermal and structural behaviors of lipids rather complex to study. Both types of properties are currently measured by X-ray diffraction and DSC. The use of a new instrument allowing simultaneously time-resolved synchrotron X-ray diffraction at both wide and small angles as a function of temperature (XRDT) and high-sensitivity DSC has been described. The advantages of collecting information from the same sample and from the same acquisition unit were also discussed. The thermal and structural properties of CB are investigated to illustrate the capabilities of the instrument (4). It is shown that in CB at room temperature, and this applies also to tempered chocolate, at least two solid phases corresponding to different TAG compositions coexist beside the liquid fatty phase. The polymorphism of both solid species is also studied. A slow heating scan at 0.1℃/min from -10 to 40℃ confirmed the existence of five of the six forms already observed. It is shown from the small-angle X-ray scattering pattern of the first phase that the least stable one, showing the coexistence of sharp lines with broad-scattering bumps, corresponds to a liquid crystalline phase in which likely the saturated chains, perfectly organized in β' form (orthorhombic packing), crystallize nearby the melted-like unorganized unsaturated chains. This liquid crystalline phase, which is also observed in palm oil submitted to the same quenching, is also found in the fractions of both fats. Concerning the second and minor phase of CB, it has been shown that it corresponds to a saturated TAG phase for which two different forms, α and β, are evidenced. Taking into account that CB is probably one of the fats showing the simplest TAG composition, it is suggested that most of the fats do not crystallize as a single form, as generally considered, but rather as a mixture of different crystals belonging to different phases. This study demonstrates that high resolution obtained at small angles using synchrotron radiation is an absolute requirement for fat polymorphism characterization. The coupling of the three techniques above might be helpful in this respect.
机译：一个或几个长链的存在，其不同的堆积导致形成多种多晶型物，使得脂质的热学和结构行为研究起来相当复杂。目前，这两种类型的性能都是通过X射线衍射和DSC测量的。已经描述了一种新仪器的使用，该仪器允许同时在广角和小角度进行时间分辨的同步加速器X射线衍射，这是温度（XRDT）和高灵敏度DSC的函数。还讨论了从同一样本和同一采集单元收集信息的优势。对CB的热和结构特性进行了研究，以说明该仪器的功能（4）。结果表明，在室温下的CB中，这也适用于回火的巧克力，在液态脂肪相旁边共存有至少两个固相，分别对应于不同的TAG组成。还研究了两种固体物种的多态性。在-10至40℃之间以0.1℃/ min的速度缓慢加热扫描，确认已经观察到六种形式中的五种。从第一相的小角度X射线散射图可以看出，最不稳定的相（显示出尖线与宽散射凸点并存）对应于液晶相，在该液晶相中，饱和链很可能组织得很好呈β'形式（斜方堆积），在熔化的，无组织的不饱和链附近结晶。在两种脂肪的馏分中也发现了这种液晶相，在棕榈油中也经历了同样的淬灭。关于CB的第二相和次要相，已经表明它对应于饱和TAG相，对于该饱和TAG相，证明了两种不同形式α和β。考虑到CB可能是显示最简单TAG组成的脂肪之一，因此建议大多数脂肪不会像通常所认为的那样以单一形式结晶，而是以属于不同相的不同晶体的混合物的形式结晶。这项研究表明，使用同步加速器辐射在小角度获得高分辨率是脂肪多态性表征的绝对要求。在这方面，上述三种技术的结合可能会有所帮助。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号