Food Safety and Preservation Department, IATA-CSIC, Avda. Agustin Escardino 7, 46980, Paterna, Valencia, Spain.
Dept. Chemistry and Chemical Engineering, Chalmers University of Technology, Gothenburg, Sweden.
Carbohydr Polym. 2020 May 15;236:115655. doi: 10.1016/j.carbpol.2019.115655. Epub 2020 Feb 21.
Agar-based extracts from Gelidium sesquipedale were generated by heat and combined heat-sonication, with and without the application of alkali pre-treatment. Pre-treatment yielded extracts with greater agar contents; however, it produced partial degradation of the agar, reducing its molecular weight. Sonication produced extracts with lower agar contents and decreased molecular weights. A gelation mechanism is proposed based on the rheological and small angle scattering characterization of the extracts. The formation of strong hydrogels upon cooling was caused by the association of agarose chains into double helices and bundles, the sizes of which depended on the agar purity and molecular weight. These different arrangements at the molecular scale consequently affected the mechanical performance of the obtained hydrogels. Heating of the hydrogels produced a gradual disruption of the bundles; weaker or smaller bundles were formed upon subsequent cooling, suggesting that the process was not completely reversible.
以石花菜为原料，分别采用加热法、热-声联合法以及碱预处理-热-声联合法提取琼胶。预处理可以提高琼胶的含量，但会导致部分琼胶降解，降低其分子量；而超声处理则会降低琼胶的含量和分子量。基于提取物的流变学和小角散射特性，提出了一种凝胶化机制。冷却时形成强水凝胶是由于琼脂糖链缔合成双链和束，其大小取决于琼胶的纯度和分子量。这些在分子尺度上的不同排列方式，进而影响了所得到的水凝胶的机械性能。水凝胶的加热会导致束的逐渐解体；随后的冷却过程中形成较弱或较小的束，表明该过程并非完全可逆。
