Abstract Quantitative ultrasound (US) techniques have an attractive potential for the non-invasive and real-time characterization of the structural and mechanical properties of food. The objective of the present study is to unravel the determinants of the variations of US properties during sol-gel transition of emulsion filled gels of agar and gelatin, due to the relative contributions (i) of their individual components and (ii) of their combined interactions. Nine model foods were designed, accounting gradually for the complexity of an emulsion filled gel composed of water, sucrose, agar, gelatin and sunflower oil. A quantitative US device was designed to monitor the sol-gel transition of the model foods. US velocity, reflectivity and attenuation were measured at 50 °C (sol-state) and 20 °C (gel-state) with a 1 MHz transducer in pulse-echo mode. US data were then compared to visco-elastic shear moduli and density measurements. Bulk elastic modulus was shown to prevail over density for explaining the variations of US velocity and reflectivity during sol-gel transition, while high gelatin concentration and interactions between agar and gelatin had an impact on US attenuation. In addition to the fact demonstrated here that US reflectivity is easier to measure compared to velocity and attenuation, the literature reports that this parameter also highly depends on the mechanical coupling of interfaces. Therefore, this study is a baseline for future investigations on the potential of US reflectivity for the characterization of physical interactions between food and more complex surfaces, so that to mimic tongue-food interaction during oral processing.

中文翻译：

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溶胶-凝胶转变对复杂模型食品超声特性的影响：应用于琼脂/明胶凝胶和乳液填充凝胶

摘要 定量超声 (US) 技术在食品结构和机械特性的非侵入性和实时表征方面具有极具吸引力的潜力。本研究的目的是阐明在琼脂和明胶的乳液填充凝胶的溶胶-凝胶转变过程中 US 特性变化的决定因素，这是由于 (i) 它们各自组分的相对贡献和 (ii) 它们的组合相互作用。设计了九种模型食品，逐渐解释了由水、蔗糖、琼脂、明胶和葵花籽油组成的乳液填充凝胶的复杂性。设计了一种定量美国装置来监测模型食物的溶胶-凝胶转变。US 速度、反射率和衰减是在 50 °C（溶胶状态）和 20 °C（凝胶状态）下用 1 MHz 换能器在脉冲回波模式下测量的。然后将美国数据与粘弹性剪切模量和密度测量值进行比较。体积弹性模量被证明优于密度，以解释溶胶-凝胶转变过程中 US 速度和反射率的变化，而高明胶浓度以及琼脂和明胶之间的相互作用对 US 衰减有影响。除了这里证明的事实，与速度和衰减相比，美国反射率更容易测量，文献报道该参数还高度依赖于界面的机械耦合。因此，这项研究是未来研究美国反射率在表征食物和更复杂表面之间的物理相互作用方面的潜力的基线，以便模拟口腔加工过程中的舌头-食物相互作用。