Phytoglycogen octenyl succinate (PG-OS) and epsilon-polylysine (EPL) were used to form oil-in-water emulsions with enhanced lipid oxidative stability. PG-OS is an amphiphilic carbohydrate nanoparticle prepared using octenyl succinate (OS) substitution of phytoglycogen (PG). PG-OS had a dispersed molecular density nearly 20 times that of waxy corn starch octenyl succinate (WCS-OS). Fish oil-in-water emulsions were prepared using PG-OS, WCS-OS, and Tween 20, stored at 55 degrees C for 6 days, and monitored for the accumulation of hydroperoxide and thiobarbituric acid reactive substances (TBARS). The result indicated that PG-OS may lead to high lipid oxidative stability, and that the addition of EPL may further improve the oxidative stability of emulsions. To address the interaction between PG-OS and EPL, zeta-potential was determined for various systems. The results indicated a possible formation of an interfacial complex layer comprising both PG-OS and EPL. This complex layer may provide both physical and electrostatic barriers against pro-oxidative compounds.

This paper reports our recent studies on the in vitro digestibility and emulsification properties of an amphiphilic carbohydrate nanoparticle, phytoglycogen octenyl succinate (PG-OS). Phytoglycogen (PG), a glycogen-like alpha-d-glucan isolated from sugary-1 sweet corn endosperms, was subjected to octenyl succinate substitution to prepare PG-OS. Waxy corn starch octenyl succinate (WCS-OS) was also prepared as the reference. The degree of substitution (DS), molecular weight, particle size, dispersed molecular density, and zeta-potential of PG-OS and WCS-OS were determined. Transmission electron microscope (TEM) was used to image PG and its derivatives. In vitro digestibility and emulsification properties of PG-OS and WCS-OS were compared. The results showed that the dispersed molecular density of PG and PG-OS was much greater than that of WCS and WCS-OS. Zeta-potential of PG-OS decreased as the pH of dispersion increased. In general, the digestibility of PG and PG-OS was lower than that of WCS and WCS-OS at equivalent DS, suggesting the effect of glucan structure on glucan digestibility. At equivalent DS, PG-OS showed similar or even greater capability than WCS-OS to physically stabilize fish oil emulsions. This work revealed the potential of amphiphilic carbohydrate nanoparticles in the applications of emulsions.