Abstract:

The porous starch was prepared via a sol-gel method and supercritical CO₂ drying with cassava starch as raw material and water and ethanol as the mixed medium. The effects of water-alcohol ratio, gelatinization time, solid content, refrigeration time, ethanol replacement amount, and replacement time on the volume shrinkage and mass-loss rate of the starch were investigated. The morphology and pore structure of porous starch were characterized by the scanning electron microscope, specific surface area and pore size distribution analyzer, and X-ray diffractometer, and the formation mechanism of starch hydrogels and the influencing factors of the porous structure were studied. The results showed that when the ratio of water to alcohol was 19∶1, the solid content was 13%, the gelatinization time was 30min, the refrigeration time was 5d, the alcohol displacement amount was 5mL/g, and the replacement time was 30min, the volume shrinkage and the mass loss of the water gel were relatively small, the specific surface area of porous dry gel reached 122m²/ g, and the average pore size was 25.6nm. SEM and N₂ adsorption-desorption analysis showed that proper adjustment of solid content could improve the three-dimensional mesh density of the gel and increase the specific surface area and pore volume. XRD results indicated the starch molecules in hydrogels could form a crystallized network skeleton, which is conducive to maintaining the stability of water-alcohol gels of starch.

Key words: cassava starch, gels, supercritical carbon dioxide, drying, porous starch

摘要：

以木薯淀粉为原料，水和乙醇为混合介质，利用溶胶-凝胶法及超临界CO₂干燥制备多孔淀粉，分别考察了水醇比、糊化时间、固含量、冷藏时间、乙醇置换用量、置换时间等对凝胶体积收缩率和质量损失率的影响，通过扫描电子显微镜、比表面积及孔径分布测试仪、X射线衍射仪表征了多孔淀粉形貌及孔结构，并考察了多孔淀粉的吸油性能。结果发现，水醇比为19∶1，固含量为13%，糊化时间为30min，冷藏时间为5天，醇置换量为5mL/g，置换时间为30min，水醇凝胶的体积收缩程度和质量损失相对较小，多孔淀粉的比表面积为122m²/g，平均孔径为25.6nm，大豆油的吸附率可达457%（质量比）。研究结果表明，适当调整固含量，能改善凝胶的三维网孔密度，增大多孔淀粉的比表面积及孔容；水醇淀粉凝胶中的淀粉分子能形成一定结晶结构的网络骨架，利于维持水醇凝胶的骨架稳定性。

关键词: 木薯淀粉, 凝胶, 超临界二氧化碳, 干燥, 多孔淀粉