Department of Food Science and Technology, Laboratory of Food Chemistry and Biochemistry School of Agriculture, Aristotle University, GR-541 24, Thessaloniki, Greece.
Biomacromolecules. 2010 Jan 11;11(1):175-81. doi: 10.1021/bm901046c.
Chitin nanocrystal aqueous dispersions were prepared by acid hydrolysis of crude chitin from crab shells. The resulting dispersions were studied with small deformation oscillatory experiments and polarized optical microscopy under different conditions of nanocrystal concentration, ionic strength, pH, and temperature. The chitin nanocrystal dispersions exhibited a nematic gel-like behavior with increasing solids concentration. The appearance of nematic-like structures could be explained by the Onsager theory for parallel alignment of anisotropic particles on entropic terms, while the sol-gel transition could be attributed to associative interactions between the chitin nanocrystals. With increasing ionic strength and pH, such associative interactions were enhanced, because the repulsive forces due to the electrostatic charges were reduced and, thus, stronger gels were formed. Heating of the nanocrystal dispersions led to further increases in the storage modulus (G'), which were irreversible upon cooling; the rate of G' increase (dG'/dt) was dependent on temperature.
壳聚糖纳米晶水分散体通过从蟹壳中提取的粗壳聚糖的酸水解制备。在纳米晶浓度、离子强度、pH 值和温度的不同条件下，通过小变形振荡实验和偏光显微镜研究了所得分散体。壳聚糖纳米晶分散体在固体浓度增加时表现出向列凝胶状行为。向列型结构的出现可以通过昂萨格理论来解释，该理论基于各向异性颗粒在熵项上的平行排列，而溶胶-凝胶转变则可以归因于壳聚糖纳米晶体之间的缔合相互作用。随着离子强度和 pH 值的增加，这种缔合相互作用得到增强，因为由于静电荷引起的排斥力减小，从而形成更强的凝胶。加热纳米晶分散体导致储能模量（G'）进一步增加，冷却后不可逆转；G'增加速率（dG'/dt）取决于温度。
