Abstract: This research was aimed to investigate the effect of acetylation and ultrafiltration on the emulsification properties of soybean soluble polysaccharides (SSPS). SSPS was used to prepare acetylated soybean soluble polysaccharides (Ac-SSPS) by acetic anhydride method. To divide Ac-SSPS into two polysaccharide components with the weight-average molecular weight (Mw) of 868.6 k and 56.8 kDa, a ceramic composite membrane with an inner diameter of 20 nm was used. The chemical structures of SSPS and Ac-SSPS were characterized by Fourier transform infrared (FT-IR) and proton nuclear magnetic resonance spectroscopy (1H NMR). The effects of acetylation and ultrafiltration on the emulsifying activities and emulsifying stabilities of polysaccharides, as well as the viscosities, creaming indexes, particle sizes and Zeta-potentials of stabilized nano-emulsions at 28 d of storage were compared and analyzed. The influences of temperature and pH on the stabilities of the emulsions were also discussed. The results showed that compared with SSPS, the emulsifying properties of Ac-SSPS increased significantly, the nano-emulsions stabilized by Ac-SSPS were more stable during storage and were less affected by temperature and pH. The Ac-SSPS with the Mw of 868.6 kDa showed the highest emulsifying activities and emulsifying stabilities. The stabilized emulsions were hardly affected by temperature and pH, and the changes of viscosities, particle sizes, Zeta-potentials were minimal during storage. In addition, there was almost no whey precipitated in its emulsion system, and the laser confocal image showed that the droplets were evenly distributed. Overall,acetylation can effectively improve the emulsifying properties of SSPS. Compared with Ac-SSPS, the high-Mw Ac-SSPS obtained after ultrafiltration showed better emulsifying properties and stabilities of nano-emulsions.
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