College of Food Sciences & Engineering, Hainan University, 58 People Road, Haikou 570228, China.
Chunguang Agro-Product Processing Institute, Wenchang 571333, China.
Molecules. 2019 Nov 29;24(23):4374. doi: 10.3390/molecules24234374.
The aim of this study was to prepare sodium alginates (SAs) with different molecular weight and G/M ratio, and characterize their rheological behaviors and emulsifying properties. The result of Fourier transform infrared (FTIR) showed that the chemical bonds among the β-d-mannuronic acid- (M-), α-l-guluronic acid- (G-), and MG-sequential blocks in the SA chains were not changed significantly by acid treatment. Meanwhile, the molecular weight and G/M ratio of the SA exhibited drastic variation after acid modification. The result of rheological analysis suggesting that the apparent viscosity of SA reduced from 30 to 16.4 mPa.s with the increase of shear rate, reveals that SA solution belongs to pseudoplastic liquid. Also, the apparent viscosity of acid-modified SA solution dropped rapidly with the decrease of the molecular weight. The properties of emulsions stabilized by SA, SA-Ms, and commercial SAs were evaluated via the interface tensiometry and determination of the zeta potential, droplet size, creaming index (CI), and Turbiscan stability index (TSI). Compared with the SA-stabilized emulsion, the interfacial tension of the emulsion stabilized by SA-M increased with the decrease of the molecular weight reduced at the similar M/G ratio. The decrease in zeta potential and the increase in TSI of the emulsion were observed with the decrease of molecular weight, indicating that molecular weight plays an important role on the emulsifying ability of SA. In addition, the SA with low G/M ratio can form emulsions with stable and fine droplets.
本研究旨在制备具有不同分子量和 G/M 比的海藻酸钠（SA），并对其流变性能和乳化性能进行表征。傅里叶变换红外（FTIR）结果表明，β-d-甘露糖酸（M）-、α-l-古洛糖酸（G）-和 MG 顺序基元在 SA 链中的化学键在酸处理后没有明显变化。同时，SA 的分子量和 G/M 比在酸改性后发生了剧烈变化。流变分析结果表明，SA 溶液的表观粘度随着剪切速率的增加从 30 降至 16.4 mPa.s，表明 SA 溶液属于假塑性液体。此外，随着分子量的降低，酸改性 SA 溶液的表观粘度迅速下降。通过界面张力和zeta 电位、粒径、乳状液分层指数（CI）和 Turbiscan 稳定性指数（TSI）的测定，评估了 SA、SA-Ms 和商业 SA 稳定的乳液的性能。与 SA 稳定的乳液相比，在相似的 M/G 比下，随着分子量降低，SA-M 稳定乳液的界面张力增加。zeta 电位的降低和 TSI 的增加表明，分子量对 SA 的乳化能力有重要影响。此外，低 G/M 比的 SA 可以形成稳定且粒径细小的乳液。
