Phosphatidylcholine-coated emulsions are unstable and prone to phase separation under certain environmental stresses, such as low pH and moderate ionic strength (>100 mmol/L NaCl). This study investigated the formation and stability of octenyl succinic anhydride-modified starch (OSAS)-stabilized nanoemulsions enhanced with phosphatidylcholine for the encapsulation of soybean oil. The effect of variables (OSAS/phosphatidylcholine weight ratio, oil composition, emulsifier concentration, etc.) and environmental stresses (pH, temperature, ionic strength, etc.) on the stability of phosphatidylcholine-enhanced nanoemulsions stabilized by OSAS was examined. Adequate addition of OSAS (OSAS/phosphatidylcholine weight ratio = 3:7) led to the formation of a more stable nanoemulsion. An emulsion at pH 2 was unstable against creaming, and no phase separation occurred after 130 h; presumably, OSAS has a certain degree of steric repulsion that protects the nanoemulsion from oiling-off. The phosphatidylcholine-enhanced nanoemulsions stabilized by OSAS were stable at high NaCl concentrations (≤800 mmol/L) and temperatures from 30 to 90 °C, which was attributed to steric and electrostatic repulsions. Transmission electron microscopy images showed that OSAS and phosphatidylcholine were both adsorbed around the surface of the emulsion. These results showed that adding OSAS could improve the formation and stability of phosphatidylcholine-stabilized emulsions.
Keywords: Environmental stress; Nanoemulsion; Octenyl succinic anhydride-modified starch; Phosphatidylcholine; Stability.
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