Preparation of Starch Stearate Ester and Stability of Pickering Emulsion

Using rice starch as raw material, starch stearate ester (SSE) was prepared by microwave-assisted method, and the SSE and its Pickering emulsion were characterized. The results showed that with the increase of stearic acid (SA) addition, the substitution degree of SSE first increased and then decreased, and the esterification reaction efficiency decreased first, then increased, and then decreased. With the increase of moisture content, the substitution degree and esterification efficiency increased first and then decreased. The effects of hydrochloric acid addition, microwave reaction time, and microwave power on the substitution degree and esterification efficiency were the same as moisture content. X-ray diffraction analysis showed that SSE still had an A-type crystalline structure. The three-phase contact angle of SSE particles increased with the increase of substitution degree. When the substitution degree was 0.0317, the contact angle was 89.6°, and SSE particles showed good oil-water amphiphilicity. The characteristics of Pickering emulsion constructed by SSE as emulsifier were studied, and the emulsification index, particle size and microstructure of the emulsion were analyzed. The results showed that when the addition of SSE was 2.5% and the volume of the oil phase was 60%, the emulsification index of Pickering emulsion was the highest, and the higher the substitution degree of SSE was, the smaller the particle size of the emulsion and the more stable the emulsion were. Particle size analysis and laser confocal microscopy observations showed that SSE could form a stable oil-in-water Pickering emulsion with a narrow droplet size distribution.