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Changes in Thermal Conduction and Mechanical Properties during Cooking Procedure of Foodstuffs due to Phase Trnsition

食品烹饪过程中因相变引起的热传导和机械性能的变化

基本信息

批准号：
15500553
负责人：
NAGAO Keiko
金额：
$ 1.92万
依托单位：
Tokyo Kasei University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2004
项目状态：
已结题

项目摘要

1)A series of experimental studies have been continued from the last project so as to describe the effect of phase transition on the mechanical properties and thermal conduction in foodstuffs during heating procedures.2)An attempt was made to follow the changes in macro- and microscopic states of starch granule in water systems during gelatinization, i.e.optical microscopic examination, DSC measurement, and observation of mechanical responses under small stresses. The results obtained indicated that the potato and wheat starch granules show much higher degree of swelling in the course of gelatinization than those from glutinous and non-glutinous rices and corns. The DSC measurement, however, revealed that the apparent heat of transition was highest with potato starch (-27.3 mJ) among the samples to be tested, while that for wheat starch was lowest (-15.2 mJ). The mechanical responses, i.e. instantaneous elasticity and steady flow viscosity, of all the samples could be characterized by a types of convex curves during the process of transition, and each maximum appeared at around 70℃ corresponding to disappearance of the crystal region in each starch molecule.3)Measurements were made to clarify the effect of phase transition of ingredients on the heat transfer in foodstuffs during heating applied to the increasing curve of temperature along the x axis from heating plane in a metal vessel. It was found that the disturbance to the increasing curve of temperature due to phase transitions, e.g.melting fats or sol transition of hydrocolloids, tends to decrease with increasing amount of thermo-insensitive materials in the samples such as cocoa powder, fiber of green tea, wheat starch granule, etc. The results suggest that the endothermic heat of transition is scattered in the increasing temperature during heating, while the course of increasing rate of temperature may be restrained by the existence of thermo-insensitive materials.

1)从上一个项目开始，继续进行了一系列的实验研究，以描述在加热过程中相变对食品机械性能和导热的影响。2)尝试跟踪淀粉颗粒在水体系中糊化过程中宏观和微观状态的变化，即光学显微镜检查、DSC测量和小应力下力学响应的观察。结果表明，马铃薯和小麦淀粉颗粒在糊化过程中的溶胀程度明显高于糯米、非糯米和玉米淀粉颗粒。DSC测定结果表明，马铃薯淀粉的表观转变热最高（-27.3 mJ），小麦淀粉的表观转变热最低（-15.2 mJ）。在转变过程中，所有样品的瞬时弹性和稳态流动粘度的力学响应均可表现为一种凸曲线，在70℃左右出现最大值，对应于每个淀粉分子中晶体区域的消失。3)应用金属容器加热平面沿x轴方向的温度上升曲线，测定了加热过程中成分相变对食品传热的影响。结果表明，随着热不敏感物质（如可可粉、绿茶纤维、小麦淀粉粒等）的加入量的增加，热不敏感物质（如脂肪熔化、胶体溶胶转变等）对温度升高曲线的干扰趋于减小。结果表明，在加热过程中，吸热转变热随温度的升高而分散，而热不敏感材料的存在可能会抑制温度升高速率的过程。