Department of Food Science, University of Guelph, Guelph, ON N1G 2W1, Canada.
Department of Food Science, University of Guelph, Guelph, ON N1G 2W1, Canada.
Food Res Int. 2019 Aug;122:209-221. doi: 10.1016/j.foodres.2019.03.070. Epub 2019 Apr 1.
The aim of this work was to address the ability of established theoretical models to describe the small deformation mechanical properties of particle-filled food protein gels. To this end, the effect of incorporating glass microspheres on the elastic modulus of heat-set whey protein isolate/xanthan gum gels is reported. Filler size and polydispersity strongly influenced the observed reinforcement with increasing filler content; however, these effects were also strongly correlated to the ionic strength of the gelator phase (0-200 mM NaCl). Fillers with greater polydispersity provided less reinforcement at high filler content, which was associated with improved packing efficiency. Increasing ionic strength reduced the extent of filler/matrix binding, drastically reducing the impact of the smaller glass microspheres (4 μm, 7-10 μm). Larger particles increased the elastic modulus at high salt content due to interfacial stress concentration and particle-particle contacts. Theoretical fits could not satisfactorily describe the general trend in reinforcement observed with increasing filler content, despite employing various methods to account for the effects of filler self-crowding. Using an empirical approach, we propose an alternative functional form which provides improved fits over the entire range of filler content investigated. This general power law (GPL) model provided physically reasonable values for the maximum packing fraction through an empirically-derived expression for the scaling exponent. A weighted average approach was also proposed to incorporate effects of imperfect filler/matrix adhesion. This method incorporates contributions of both bound and unbound fillers, providing a means to model the effect of increasing ionic strength.
这项工作的目的是研究已建立的理论模型在描述填充颗粒的食品蛋白质凝胶的小变形力学性能方面的能力。为此，报告了在热定的乳清蛋白分离物/黄原胶凝胶中加入玻璃微球对弹性模量的影响。填料粒径和多分散性强烈影响观察到的增强效果，随着填料含量的增加而增强；然而，这些影响也与凝胶剂相的离子强度（0-200mM NaCl）强烈相关。具有较大多分散性的填料在高填料含量下提供的增强效果较小，这与改善的填充效率有关。增加离子强度会降低填料/基质结合的程度，从而大大降低较小玻璃微球（4μm、7-10μm）的影响。较大的颗粒由于界面应力集中和颗粒间接触，在高盐含量下会增加弹性模量。尽管采用了各种方法来考虑填料自拥挤的影响，但理论拟合并不能令人满意地描述随着填料含量增加而观察到的增强的一般趋势。通过对标度指数进行经验推导，我们提出了一种替代的功能形式，该形式提供了在整个填料含量范围内的改进拟合。这种通用幂律（GPL）模型通过经验推导的标度指数表达式为最大填充分数提供了合理的物理值。还提出了一种加权平均方法来纳入不完善的填料/基质附着力的影响。该方法结合了结合和未结合填料的贡献，为模拟离子强度增加的效果提供了一种手段。
