基于天然甘草酸纳米纤维的多维组装制备食品级超稳态泡沫

Preparation of Food-grade Ultrastable Foam via Multi-dimensional Assembly of Natural Saponin Glycyrrhizic Acid Nanofibers

摘要:

本研究使用天然甜味剂甘草酸（Glycyrrhizic acid, GA）作为起泡稳定剂制备超稳态的泡沫材料。在高温均质过程中，GA自组装纳米纤维可快速吸附到气泡表面并形成多层界面纤维膜；随后快速冷却使体相中未吸附的GA纤维通过氢键组装成水凝胶网络，快速诱捕与固定气泡单元，稳定泡沫结构。稳定性测试显示当GA纤维浓度大于4 wt%时，可形成超稳定泡沫，室温放置3个月后无明显变化。微观结构观察结果表明，随着GA纤维浓度提高，气泡尺寸减小且更均匀，覆盖气泡表面的纤维层更紧密。流变学测试结果也显示，随着GA纤维浓度提高，泡沫结构有更强的粘弹性响应，高纤维浓度下制备的泡沫有更高的粘弹性模量（G′和G″）值（1 wt% GA的G′为5.954，G″为4.084；8 wt% GA的G′为1.6098×104，G″为5.995×103）及屈服应力值（1 wt% GA为8.087，8 wt% GA为8.982×102）。本研究结果表明，天然皂苷GA纤维可作为一种新型起泡剂用于制备超稳定泡沫，且该体系起泡性高，制备方法简单温和，在食品、药品和化妆品等领域具有宽阔的应用前景。

Abstract:

In this work, ultrastable foams were prepared by using the naturally occurring saponin glycyrrhizic acid (GA) as the foam stabilizer. In the process of homogenization at high temperature, the self-assembled GA fibrils could be rapidly adsorbed onto the the surface of the bubbles and form a multilayered interfacial fiber film. Then, rapid cooling enabled the unadsorbed fibrils were further self-organized into a hydrogel network through hydrogen bonding in the continuous phase, by which the bubbles were trapped and fixed (thereby forming stable foams). The stability tests showed that when the GA nanofibril concentration was greater than 4 wt%, ultrastable foams could be formed (which remained unchanged at room temperature (25 ℃) over 3 months. Microstructural observations revealed that with the increase of nanofibril concentration, the size of bubbles became smaller and more uniform and the fiber layers on the surface of the bubbles were more compact. The rheological results also showed that with the increase of GA nanofibril concentration, the foams exhibited a stronger viscoelastic respond, and the foam prepared at a high fiber concentration had higher viscoelastic moduli (G′ and G?): At 1 wt% and 8 wt% GA, respectively, G′ and G″were 5.954 and 4.084,. 1.6098×104 and 5.995×103, respectively, whereas, the yield stress were 8.087 and 8.982×102 respectively. These results indicated that the naturally occurring saponin GA could be used as a new type of foaming agent for the preparation of ultrastable foams with high formability. The preparation method was simple and uses mild conditions thus may have a broad prospective applications in food, pharmaceutical, cosmetic and other fields.