The effect of amylose/amylopectin ratio on the stability of starch-O/W emulsion

Multi-component oil-in-water (O/W) emulsions co-stabilized by pre-gelatinized starches with different amylose/amylopectin (A/A) ratios, including high-amylopectin corn starch (HAS, A/A ratio: 0.062), potato starch (PTS, A/A ratio: 0.455) and pea starch (PES, A/A ratio: 1.700), and soy protein isolate (SPI) were prepared and the physicochemical properties (e.g. droplet size, zeta-potential, microstructure and apparent viscosity) of the samples were fully investigated.

The volume-weighted mean diameter (d_4,3), surface-weighted mean diameter (d_3,2), emulsion stability and negative zeta-potential decreased at the same content of starch as the A/A ratio increased. Confocal laser scanning microscopy revealed that that the droplet distribution of SPI-HAS group was the most uniform, whereas that of SPI-PES group was the most aggregated. After starch gelatinization, a gel network was formed and dispersed in the aqueous phase, with emulsion droplets embedded within the network. Fourier transform infrared spectrometer and fluorescence spectroscopy confirmed that starches and SPI combined primarily through hydrogen bonds and non-covalent interactions. The intensity of the amide bands decreased with the addition of starches, indicating that starch formed hydrogen bonds. The amide band weakened as the A/A ratio decreased. Starches with negative charges have the ability to promote the adsorption of SPI on the surface of oil droplets, resulting in improved emulsion stability, which increased as the A/A ratio decreased.

The interaction between pre-gelatinized starches with different A/A ratios and SPI significantly affects the overall stability of O/W emulsions. © 2026 Society of Chemical Industry.