Institute of Food Technology, University of Natural Resources and Life Sciences (BOKU), Muthgasse 18, 1190Vienna, Austria.
Food Colloids Group, School of Food Science and Nutrition, University of Leeds, LeedsLS2 9JT, U.K.
Biomacromolecules. 2023 Jan 9;24(1):69-85. doi: 10.1021/acs.biomac.2c00881. Epub 2022 Dec 2.
Extrusion-based 3D printing has emerged as the most versatile additive manufacturing technique for the printing of practically any material. However, 3D printing of functional materials often activates thermo-mechanical degradation, which affects the 3D shape quality. Herein, we describe the structural changes of eight different starch sources (normal or waxy) as a consequence of the temperature of an extrusion-based 3D printing system through in-depth characterization of their molecular and structural changes. The combination of size-exclusion chromatography, small-angle X-ray scattering, X-ray diffraction, dynamic viscoelasticity measurements, and digestion has offered an extensive picture of the structural and biological transformations of starch varieties. Depending on the 3D printing conditions, either gelatinization was attained ("moderate" condition) or single-amylose helix formation was induced ("extreme" condition). The stiff amylopectin crystallites in starch granules were more susceptible to thermo-mechanical degradation compared to flexible amorphous amylose. The crystalline morphology of the starch varieties varied from B-type crystallinity for the starch 3D printing at the "moderate" condition to a mixture of C- and V-type crystallinity regarding the "extreme" condition. The "extreme" condition reduced the viscoelasticity of 3D-printed starches but increased the starch digestibility rate/extent. In contrast, the "moderate" condition increased the viscoelastic moduli, decreasing the starch digestion rate/extent. This was more considerable mainly regarding the waxy starch varieties. Finally, normal starch varieties presented a well-defined shape fidelity, being able to form a stable structure, whereas waxy starches exhibited a non-well-defined structure and were not able to maintain their integrity after printing. The results of this research allow us to monitor the degradability of a variety of starch cultivars to create starch-based 3D structures, in which the local structure can be controlled based on the 3D printing parameters.
挤出式 3D 打印已成为最通用的增材制造技术，可用于打印几乎任何材料。然而，功能材料的 3D 打印通常会激活热机械降解，从而影响 3D 形状质量。在此，我们通过深入研究其分子和结构变化，描述了八种不同淀粉源（普通或蜡质）作为挤出式 3D 打印系统温度的结果的结构变化。尺寸排阻色谱法、小角 X 射线散射、X 射线衍射、动态粘弹性测量和消化的结合，提供了淀粉品种结构和生物转化的广泛图片。根据 3D 打印条件，要么达到了糊化（“中等”条件），要么诱导了单直链淀粉螺旋形成（“极端”条件）。与柔性无定形直链淀粉相比，淀粉颗粒中刚性支链淀粉结晶更易受到热机械降解的影响。淀粉品种的结晶形态从“中等”条件下的淀粉 3D 打印的 B 型结晶度变化为“极端”条件下的 C 和 V 型结晶度的混合物。“极端”条件降低了 3D 打印淀粉的粘弹性，但增加了淀粉消化率/程度。相比之下，“中等”条件增加了粘弹性模量，降低了淀粉消化率/程度。对于蜡质淀粉品种，这种情况更为明显。最后，普通淀粉品种表现出良好的形状保真度，能够形成稳定的结构，而蜡质淀粉表现出非明确的结构，并且在打印后无法保持其完整性。这项研究的结果使我们能够监测各种淀粉品种的降解性，以创建基于淀粉的 3D 结构，其中可以根据 3D 打印参数控制局部结构。
