用动态机械测析仪研究面团的热流变特性

THERMAL RHEOLOGICAL PROPERTIES OF FLOUR-WATER DOUGH MEASURED WITH A DYNAMIC MECHANICAL ANALYZER

使用动态机械测析仪 ,研究了面团在加热过程中 ( 2 5～ 1 0 0℃ )的动态热流变特性 .结果表明面团动态弹性模量 (E′)随温度呈三阶段模式变化 ,在第一阶段 ( 2 5～ 5 0℃ ) ,E′缓慢增长 ;在第二阶段E′迅速增大 ,约 75℃时达到峰值 ;在第三阶段 ( 75～ 1 0 0℃ )E′迅速减少 .面团加水量从 5 8%增加到 66% ,E′值减少 ;而E′达到峰值时的温度略有降低 .在 1～ 1 0Hz动态频率和 1 5～ 30mN的静态测试力范围内 ,面团的热流变特性变化被DMA敏感地检测到 ,随探测力减少其检测噪音增大 ,随频率增大检测敏感性降低 。

Thermal rheological properties of flour-water dough were measured using a dynamic mechanical analyzer(DMA) with a 10-mm parallel plate-cup measurement geometry in the compression mode over a temperature range from 25 to 100℃ at 5℃/min increments.The temperature-dependent dynamic rheological changes of dough during heating followed a three-stage pattern.The dynamic storage modulus(E')increased slowly in the first stage(25-50℃),increased rapidly in the second stage to reach its peak value at about 75℃,and then decreased rapidly in the third stage(75-100℃).The E' peak value decreased as water absorption of the dough increased from 58 to 66%,whereas the peak temperature decreased slightly with increased water absorption.The thermal rheological changes in dough were detected sensitively by DMA in the probing forces rangs of 15 to 30 mN at a dynamic force frequency range of 1-10 Hz.Measurement noise increased as probing force decreased,and measurement sensitivity decreased as frequency increased.Storage modulus values increased as probing force and frequency increased