Properties and mechanisms of O/W emulsions stabilized by shellac and xanthan gum at acidic pH.

Shellac (SL) is a potential natural emulsifier but is not soluble at acidic pH. This study examined creating acid-stable emulsions by adding xanthan gum (XG) to SL-based emulsions. Using shear homogenization and ultrasonication, stable emulsions were achieved at acidic pH with a 1:4 SL:XG mass ratio and 10 % v/v soybean oil. Visual stability was observed at pH 3.5-7.5 after 30-day ambient storage, although with slight droplet size increases. At pH 3.5, heating above 70 °C caused droplet growth and creaming, highlighting the importance of solid-state SL structure in stabilizing the interface. Atomic force microscopy suggested that the XG network at pH 3.5 likely created a yield stress that prevented oil droplet aggregation and subsequent creaming. Electrostatic repulsion mainly stabilized the droplets, with hydrogen bonding and hydrophobic interaction possibly contributing to XG-SL complexation. Findings from the present study may illustrate the mechanism of polysaccharides stabilizing SL-based emulsions at acidic pH.