Department of Physics & Astronomy, University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2.
Colloids Surf B Biointerfaces. 2013 Dec 1;112:466-73. doi: 10.1016/j.colsurfb.2013.05.032. Epub 2013 Jun 19.
Understanding interactions between interfaces and biopolymers in complex industrially processed materials of plant origin will allow for their better utilization. Wheat flour doughs are one such material whose industrial use strongly depends on such interactions due to their effect on the mechanical properties of the dough. To date, mechanical characterizations of dough have been limited to a narrow range of frequencies. Here, ultrasonic spectroscopy measurements over a very broad frequency range are used to show that a fast volumetric relaxation occurs in dough; the nanosecond timescale of the relaxation is associated with ultrasonic stress-induced changes in the secondary structure of gluten proteins. Interestingly, there is a four-fold difference in the speed of this relaxation phenomenon in doughs mixed in air (where substantial internal interfacial area exists) compared to those mixed under vacuum (where bubbles are absent). Given the large internal interfacial area in dough, the amphiphilic proteins residing at gas bubble interfaces significantly alter the high-frequency mechanical response of this important material.
理解界面和生物聚合物在复杂的工业加工植物源材料中的相互作用，将有助于更好地利用这些材料。小麦面团就是这样一种材料，由于其对面团机械性能的影响，其工业用途强烈依赖于这种相互作用。迄今为止，面团的机械特性仅限于很窄的频率范围。在这里，使用非常宽的频率范围的超声光谱测量来表明面团中发生快速体积弛豫；弛豫的纳秒时间尺度与超声应力诱导的面筋蛋白二级结构变化有关。有趣的是，在空气中混合的面团（其中存在大量的内部界面区域）和在真空中混合的面团（其中不存在气泡）中，这种弛豫现象的速度相差四倍。鉴于面团中存在很大的内部界面区域，驻留在气泡界面处的两亲性蛋白质会显著改变这种重要材料的高频机械响应。
