Department of Chemical Engineering, Indian Institute of Technology, Madras, India.
Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai, India.
Phys Chem Chem Phys. 2022 Sep 28;24(37):22691-22698. doi: 10.1039/d2cp01479c.
Plant cell walls undergo multiple cycles of dehydration and rehydration during their life. Calcium crosslinked low methoxy pectin is a major constituent of plant cell walls. Understanding the dehydration-rehydration behavior of pectin gels may shed light on the water transport and mechanics of plant cells. In this work, we report the contributions of the microstructure to the mechanics of pectin-Ca gels subjected to different extents of dehydration and subsequent rehydration. This is investigated using a pectin gel composition that forms 'egg-box bundles', a characteristic feature of the microstructure of low methoxy pectin-Ca gels. Large amplitude oscillatory shear (LAOS) rheology along with small angle neutron scattering and near infrared (NIR) spectroscopy on pectin gels is used to elucidate the mechanical and microstructural changes during dehydration-rehydration cycles. As the extent of dehydration increases, the reswelling ability, strain-stiffening behavior and yield strain decrease. These effects are more prominent at faster rates of dehydration and are not completely reversible upon rehydration to the initial undried state. Microstructural changes due to the aggregation of egg-box bundles and single chains and the associated changes in the water configurations lead to these irreversible changes.
在其生命周期中，植物细胞壁会经历多次脱水和再水化循环。钙交联的低甲氧基果胶是植物细胞壁的主要成分。了解果胶凝胶的脱水-再水化行为可以揭示植物细胞的水分传输和力学性质。在这项工作中，我们报告了微观结构对经历不同程度脱水和随后再水化的果胶-Ca 凝胶力学性能的贡献。这是通过使用一种形成“蛋盒束”的果胶凝胶组成来研究的，这是低甲氧基果胶-Ca 凝胶微观结构的一个特征。使用大振幅振荡剪切（LAOS）流变学以及小角中子散射和近红外（NIR）光谱对果胶凝胶进行研究，以阐明在脱水-再水化循环过程中的力学和微观结构变化。随着脱水程度的增加，溶胀能力、应变硬化行为和屈服应变减小。这些影响在脱水速度较快时更为显著，并且在重新水化到初始未干燥状态时并非完全可逆。由于蛋盒束和单链的聚集以及相关的水配置变化引起的微观结构变化导致了这些不可逆的变化。
