Cassanelli Mattia, Norton Ian, Mills Tom
School of Chemical Engineering, University of Birmingham, Edgbaston, Birmingham, B15 2TT UK.
Food Biophys. 2018;13(3):304-315. doi: 10.1007/s11483-018-9536-5. Epub 2018 May 22.
The effect of sucrose and mannitol addition to low-acyl (LA) gellan gum gels at both the molecular and macroscopic levels prior to, and after freeze-drying has been investigated. It has been shown that the gel network order as well as the mechanical properties are changed with the solute content, especially in the case of sucrose. The freeze-dried gel structure, containing either mannitol or sucrose, was studied, reporting for the first time the interaction of mannitol with the gellan gum gel. The generated freeze-dried gel network was evaluated in terms of porosity, pore size and wall thickness distributions. The solute physical state was correlated the water activity trend as a function of the solute content. Since mannitol is crystalline, the water activity decreases, in contrast with the amorphous sucrose. The rehydration mechanism was investigated and associated with the solute release from the structure. Specifically, the material properties (surface and bulk) as well as the role of the dissolution medium over time were assessed. It was found that the rehydration for both the gellan/sucrose and gellan/mannitol systems was highly influenced by the additive content, as an increase in water uptake was measured up to 10 wt%. A further increase in solute led to a considerable drop in the rehydration rate and extent due to the change in the freeze-dried structure, with smaller pores and with higher wall thickness values.
研究了在冷冻干燥前后，添加蔗糖和甘露醇对低酰基（LA）结冷胶凝胶在分子和宏观层面的影响。结果表明，凝胶网络有序度以及机械性能会随溶质含量而变化，蔗糖的情况尤其如此。对含有甘露醇或蔗糖的冷冻干燥凝胶结构进行了研究，首次报道了甘露醇与结冷胶凝胶的相互作用。从孔隙率、孔径和壁厚分布方面对生成的冷冻干燥凝胶网络进行了评估。溶质的物理状态与作为溶质含量函数的水分活度趋势相关。由于甘露醇是结晶态的，与无定形的蔗糖不同，其水分活度会降低。对复水机制进行了研究，并将其与溶质从结构中的释放联系起来。具体而言，评估了材料性能（表面和体相）以及溶解介质随时间的作用。结果发现，结冷胶/蔗糖和结冷胶/甘露醇体系的复水受到添加剂含量的高度影响，因为在溶质含量高达10 wt%时，吸水量会增加。溶质的进一步增加会导致复水速率和程度大幅下降，这是由于冷冻干燥结构发生了变化，孔隙变小且壁厚值更高。
