Starch nanoparticles produced via acidic dry heat treatment as a stabilizer for a Pickering emulsion: Influence of the physical properties of particles

To evaluate the effect of the starch particle size on the stability of a Pickering emulsion, starch particles with various mean diameters were prepared using dry heat treatment under mildly acidic conditions. As addition level of acid increased, mean diameter of starch particles decreased from 23,100 to 15.7 nm, and contact angle of water droplet on the starch film increased from12 to 42.7 degrees. Confocal microscopy revealed that a cohesive layer of starch particles with diameter of 28.6 nm surrounded the oil droplets, which may stabilize the emulsion. For starch particles smaller than 33.5 nm, the emulsion stability index increased up to approximately 95 % when starch content was higher than 9.1 %. For 16.7 % starch content, starch particles (< 33.5 nm) could form a stable emulsion with oil content of up to 61 %. For the emulsion stabilized by starch with 28.6 nm, it was stable when subjected to heating and freeze-thawing treatment.