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首页> 外文学位 >Modeling thermal and mechanical effects of extrusion on thiamin retention in extruded wheat flour.
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Modeling thermal and mechanical effects of extrusion on thiamin retention in extruded wheat flour.

机译：模拟挤出对挤出的小麦粉中硫胺素保留的热和机械效应。

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摘要

Average shear rate ( ga&d2; ) of a twin-screw co-rotating extruder was investigated to calculate shear history---a factor to model the mechanical effect (R S) of extrusion. Fluids with different flow behavior indices, which represent different feed materials, were extruded at degrees of fill ranging from 0.4--1.0. Using mixer viscometry assumptions, ga&d2; was estimated and then modeled as a function of screw speed and degree of fill.; To calculate extrusion thermal effects on thiamin degradation ( Rbeta), kinetic parameters were obtained by heating flour, mixed with thiamin, at temperatures >100°C in a shearless environment. Two methods (atmospheric and controlled-pressure) to obtain the parameters were compared. The results from the two methods were not statistically different. The parameters obtained from the controlled-pressure method had lower standard error; for 25% moisture content flour, activation energy was 121.0 kJ/g-mol and reaction rate at 80°C was 9.69E-5 min-1.; For extrusion, the same thiamin flour mixture was extruded at screw speeds of 100--300 rpm at two temperatures profiles. R beta was calculated using the thiamin kinetic parameters. RS was calculated by mathematically removing Rbeta from the total thiamin retention. At higher temperature, thermal effects predominated over mechanical effects for thiamin loss, while at lower temperature, mechanical effects slightly prevailed over thermal effects. Mechanical effects caused 28.9% to 64.5% of total thiamin loss.
机译：研究了双螺杆同向旋转挤出机的平均剪切速率（ga＆d2;），以计算剪切历史-一个模拟挤出机械效应（R S）的因素。代表不同进料的具有不同流动行为指数的流体以0.4--1.0的填充度挤出。使用混合器粘度假设，ga＆d2;。进行估算，然后将其建模为螺杆速度和填充度的函数。为了计算挤出对硫胺素降解的热效应（Rbeta），通过在无剪切环境中于> 100°C的温度下加热与硫胺素混合的面粉获得动力学参数。比较了获得参数的两种方法（大气压和受控压力）。两种方法的结果无统计学差异。从控制压力法获得的参数具有较低的标准误差。对于水分含量为25％的面粉，活化能为121.0kJ / g-mol，在80℃下的反应速率为9.69E-5min-1。为了挤出，将相同的硫胺粉混合物在两个温度曲线下以100--300 rpm的螺杆速度挤出。使用硫胺素动力学参数计算R beta。通过数学上从总硫胺素保留中去除Rbeta来计算RS。在较高温度下，硫胺素损失的热效应高于机械效应，而在较低温度下，机械效应略胜于热效应。机械效应导致了总硫胺素损失的28.9％至64.5％。

著录项

  • 作者

    Suparno, Maria.;

  • 作者单位

    Michigan State University.;

  • 授予单位 Michigan State University.;
  • 学科 Engineering Agricultural.; Agriculture Food Science and Technology.
  • 学位 M.S.
  • 年度 2004
  • 页码 170 p.
  • 总页数 170
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 农业工程;农产品收获、加工及贮藏;
  • 关键词

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