Preparation of catechin-starch nanoparticles composites and its application as a Pickering emulsion stabilizer

Starch is a biopolymer commonly used for nanoparticle synthesis. Starch nanoparticles (SNPs) have potential as encapsulation agents and Pickering emulsion stabilizers. Here, we prepared SNPs by dry heating under mildly acidic conditions to encapsulate catechin. Catechin (30 mg) and SNPs (50-150 mg) were dispersed in distilled water and freeze-dried to prepare catechin-SNP composites. Isothermal titration calorimetry and Fourier-transform infrared spectroscopy revealed that the binding of catechin to SNP may involve spontaneous hydrogen bonding and hydrophobic interactions. SNPs exhibited encapsulation efficiency for catechin, with 100 % catechin retention when 150 mg of SNP was used to prepare the composites. The catechin-SNP composites had a particle size of 54.2-74.9 nm. X-ray diffraction analysis revealed the formation of small amounts of inclusion complexes in catechin-SNP composites. As the amount of SNPs added for encapsulation increased, the catechin encapsulated in the SNP composites exhibited higher water solubility and UV stability than the pure catechin. The catechin-SNP composite with 150 mg of catechin exhibited the highest contact angle (51.37°) and formed a stable emulsion without notable droplet size changes. Therefore, catechin-SNP composites improved the encapsulation efficiency, water-solubility, stability of catechins, and Pickering emulsion stability.