3D food printing is an emerging technology with a potential to influence the food manufacturing sector. Rheological properties of food inks are critical for their successful 3D printing. However, the relationships between rheological properties and 3D printability have not been clearly defined in food systems. In this work, a gel model system composed of carrageenan-xanthan-starch was prepared for an extrusion-based 3D food printer. The 3D printing process was divided into three stages and the corresponding rheological properties of inks for each stage were determined, namely extrusion stage (yield stress, viscosity and shear-thinning behaviour), recovery stage (shear recovery and temperature recovery properties) and self-supporting stage (complex modulus G* and yield stress at room temperature). Finally, 3D printability of the model inks was systematically studied starting with printing lines/pentagram (one dimensional, 1D structure) to printing lattice scaffold (two dimensional, 2D structure) and finally printing cylinders (three dimensional, 3D structure). Results demonstrated that addition of starch and xanthan gum in k-carrageenan based inks increased inks’ gelation temperature (Tgelation), viscosity (within shear rate of 0.01–100 1/s), yield stress, G* enhanced shear-thinning (thixotropic) behaviour and reduced time-dependence of modulus (temperature recovery). Rheological responses of yield stress (cross-over point where G′ (elastic modulus) equals to G′′ (viscous modulus) in the stress sweep tests) and shear-thinning behaviour (viscosity decreased when shear rate increased) were closely related to ink's extrudability. Inks’ gelation temperature (Tgelation) and time-dependent behaviour (gelation time, tgel) significantly affected their printability and shape retention performance. The mechanical strength of the ink is important to be self-supporting, especially for 3D structures. Insights achieved from this study could provide guidance on improving 3D printability of foods that use hydrocolloids as a printing aid.

中文翻译：

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将角叉菜胶-黄原胶-淀粉多组分凝胶系统的流变学和可印刷性联系起来，用于基于挤出的增材制造

3D 食品打印是一项新兴技术，有可能影响食品制造业。食品油墨的流变特性对其成功的 3D 打印至关重要。然而，流变特性和 3D 可打印性之间的关系在食品系统中尚未明确定义。在这项工作中，为基于挤出的 3D 食品打印机制备了由角叉菜胶-黄原胶-淀粉组成的凝胶模型系统。3D打印过程分为三个阶段，并确定了每个阶段油墨的相应流变特性，即挤出阶段（屈服应力、粘度和剪切稀化行为）、恢复阶段（剪切恢复和温度恢复特性）和自恢复。支撑阶段（复数模量 G* 和室温下的屈服应力）。最后，从打印线/五角星（一维，一维结构）到打印晶格支架（二维，2D 结构），最后是打印圆柱体（三维，3D 结构），系统地研究了模型墨水的 3D 可打印性。结果表明，在基于 k-卡拉胶的油墨中添加淀粉和黄原胶可提高油墨的胶凝温度 (Tgelation)、粘度（在 0.01–100 1/s 的剪切速率内）、屈服应力、G* 增强剪切稀化（触变性）行为和降低模量的时间依赖性（温度恢复）。屈服应力（应力扫描试验中 G'（弹性模量）等于 G''（粘性模量）的交叉点）和剪切稀化行为（剪切速率增加时粘度降低）的流变响应与油墨的可挤出性。油墨的胶凝温度 (Tgelation) 和随时间变化的行为（胶凝时间，tgel）显着影响了它们的印刷适性和保形性能。油墨的机械强度对于自支撑很重要，尤其是对于 3D 结构。从这项研究中获得的见解可以为改善使用水胶体作为打印助剂的食品的 3D 可打印性提供指导。