Formation of Smilax glabra starch-fatty acid complexes and their application in Pickering emulsions

Natural starch granules exhibit limited stability in Pickering emulsions due to their strong surface hydrophilicity. In this study, debranched Smilax glabra starch was used as a matrix to prepare starch-fatty acid complexes (SGS-LA, SGS-LOA, and SGS-SA) by complexation with lauric acid (LA), linoleic acid (LOA), and stearic acid (SA), respectively. Their physicochemical properties and emulsification performance were systematically evaluated. Scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction analyses indicated that these complexes formed Ⅴ-type crystalline structure through non-covalent interactions. Among them, SGS-LA exhibited the highest complex index (46.07%), with an average particle size of 114.30 μm and a contact angle of 68.71°. In the Pickering emulsions system, SGS-LA demonstrated the best emulsifying performance. Under the conditions of 80% oil phase volume fraction and 2% particle concentration, the emulsion stabilized by SGS-LA had the smallest droplet size (approximately 10 μm) and the highest emulsification index (82.87%). Environmental stability evaluation further revealed that neutral pH and low ionic strength (0-25 mmol·L^-1) were conducive to emulsion stability. This study demonstrates that short-chain fatty acids facilitate the formation of starch-fatty acid complexes with small particle size and good emulsification performance, while also highlighting the important influence of environmental conditions on emulsion stability. These findings provide new insights for developing sustainable natural emulsifiers.