Kumbár Vojtěch, Kouřilová Veronika, Dufková Renáta, Votava Jiří, Hřivna Luděk
Department of Technology and Automobile Transport (Section Physics), Faculty of AgriSciences, Mendel University in Brno, Zemědělská 1, 613 00 Brno, Czech Republic.
Department of Food Technology, Faculty of AgriSciences, Mendel University in Brno, Zemědělská 1, 613 00 Brno, Czech Republic.
Foods. 2021 Oct 20;10(11):2519. doi: 10.3390/foods10112519.
Chocolate masses are one of the basic raw materials for the production of confectionery. Knowledge of their rheological and flow behaviour at different temperatures is absolutely necessary for the selection of a suitable technological process in their production and subsequent processing. In this article, the rheological properties (the effect of the shear strain rate on the shear stress or viscosity) of five different chocolate masses were determined-extra dark chocolate (EDC), dark chocolate (DC), milk chocolate (MC), white chocolate (WC), and ruby chocolate (RC). These chocolate masses showed thixotropic and plastic behaviour in the selected range of shear rates from 1 to 500 s and at the specified temperatures of 36, 38, 40, 42, and 44 °C. The degree of thixotropic behaviour was evaluated by the size of the hysteresis area, and flow curves were constructed using the Bingham, Herschel-Bulkley and Casson models with respect to the plastic behaviour of the chocolate masses. According to the values of the coefficients of determination R and the sum of the squared estimate of errors (SSE), the models were chosen appropriately. The most suitable models are the Herschel-Bulkley and Casson models, which also model the shear thinning property of the liquids (pseudoplastic with a yield stress value). Using the coefficients of the rheological models and modified equations for the flow velocity of technical and biological fluids in standard piping, the 2D and 3D velocity profiles of the chocolate masses were further successfully modelled. The obtained values of coefficients and models can be used in conventional technical practice in the design of technological equipment structures and in current trends in the food industry, such as 3D food printing.
巧克力浆是生产糖果的基本原料之一。了解它们在不同温度下的流变学和流动行为对于在其生产和后续加工中选择合适的工艺过程绝对必要。在本文中，测定了五种不同巧克力浆的流变特性（剪切应变率对剪切应力或粘度的影响）——特纯黑巧克力（EDC）、黑巧克力（DC）、牛奶巧克力（MC）、白巧克力（WC）和红宝石巧克力（RC）。这些巧克力浆在1至500 s的选定剪切速率范围内以及在36、38、40、42和44°C的指定温度下表现出触变性和塑性行为。通过滞后面积的大小评估触变性程度，并针对巧克力浆的塑性行为使用宾汉、赫谢尔 - 巴克利和卡森模型构建流动曲线。根据决定系数R的值和误差平方和估计值（SSE），适当选择模型。最合适的模型是赫谢尔 - 巴克利模型和卡森模型，它们也对液体的剪切变稀特性（具有屈服应力值的假塑性）进行建模。利用流变模型的系数以及标准管道中技术和生物流体流速的修正方程，进一步成功模拟了巧克力浆的二维和三维速度分布。获得的系数和模型值可用于传统技术实践中工艺设备结构的设计以及食品工业的当前趋势，如3D食品打印。
