Simultaneous and in situ analysis of thermal and volumetric properties of starch gelatinization over wide pressure and temperature ranges.
Simultaneous and in situ analysis of thermal and volumetric properties of starch gelatinization over wide pressure and temperature ranges.
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在较宽的压力和温度范围内对淀粉糊化的热和体积特性进行同步和原位分析。
DOI：
10.1021/bm0503569
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发表时间：
2005
影响因子：
6.2
通讯作者：
M. Orłowska
中科院分区：
文献类型：
--
作者：
S. Randzio;M. Orłowska
本文介绍了一种在0.1 ~ 100 MPa、283 ~ 430 K范围内对淀粉糊化过程的热性质和体积性质进行同时和原位分析的方法。在选定的压力下，含有淀粉-水乳液的非常灵敏的量热检测器的温度被编程为以缓慢的速度上升;自动进行体积变化，以保持选定的压力恒定，同时记录热交换速率和体积。该方法被证明与一个新的调查压力的影响在一个序列的三个相变的小麦淀粉（56重量%的水）的水乳液。主要吸热转变（M）期间的体积变化，与淀粉颗粒的结晶部分的熔融和支链淀粉中的螺旋-卷曲转变有关，但也与重要的溶胀有关，被分成与溶胀有关的体积增加和与转变本身有关的体积减少。这种转变的热力学参数，连同它们的压力依赖性已获得从四个独立的实验，在每个压力。这些数据在化学上是一致的，但用克拉珀龙方程描述得很差。在主吸热转变（M）之后出现的缓慢放热转变（A）的负体积变化很小，在很宽的温度区间上展开，并且随着压力的增加在较高的温度下发生。这种转变可能与支链淀粉的解旋螺旋与支链淀粉分子的部分而不是其原始螺旋双链体伴侣的再结合有关。具有小焓变的高温吸热转变（N）的正体积变化可能与结束形成均匀SOL相（在Flory意义上）的向列-各向同性转变相关，并且还随着压力的增加被推到更高的温度。了解小麦淀粉的状态作为压力和温度的函数在挤压机加工中是重要的。这些数据也为淀粉糊化的椭圆相图提供了依据。该方法很容易适用于确定其他高分子材料的类似数据。
A method for simultaneous and in situ analysis of thermal and volumetric properties of starch gelatinization from 0.1 to 100 MPa and from 283 to 430 K is described. The temperature of a very sensitive calorimetric detector containing a starch-water emulsion at a selected pressure is programmed to rise at a slow rate; volume variations are performed automatically to keep the selected pressure constant while the heat exchange rate and the volume are recorded. The method is demonstrated with a novel investigation of pressure effects on a sequence of three phase transitions in an aqueous emulsion of wheat starch (56 wt % water). The volume changes during the main endothermic transition (M), associated with melting of the crystalline part of the starch granules and a helix-coil transformation in amylopectin, but also with an important swelling, were separated into a volume increase associated with swelling and a volume decrease associated with the transition itself. Thermodynamic parameters for this transition together with their pressure dependencies have been obtained from four independent experiments at each pressure. The data are thermodynamically consistent, but are poorly described by the Clapeyron equation. The negative volume change of the slow exothermic transition (A) appearing just after the main endothermic transition (M) is small, spread out over a wide temperature interval, and occurs at higher temperatures with increasing pressures. This transition is probably associated with reassociation of the unwound helixes of amylopectin with parts of amylopectin molecules other than their original helix duplex partner. The positive volume change of the high-temperature, endothermic transition (N) with a small enthalpy change is probably associated with a nematic-isotropic transformation ending the formation of a homogeneous SOL phase (in the sense of Flory), and is also pushed to higher temperatures with increasing pressures. Knowledge of the state of wheat starch as a function of pressure and temperature is important in extruder processing. The data also provide a basis for the elliptic phase diagram for starch gelatinization. The method is easily adapted to determine similar data for other macromolecular materials.