Intermittent ultrasound-assisted anti-solvent crystallization for sucralose production with ultra-low aspect ratio and larger crystal size

Abstract

The simultaneous achievements of lower aspect ratio and larger crystal size is urgent for the production of high-quality sucralose. In this work, non-toxic ethanol-based anti-solvent crystallization (ASC) of sucralose was conducted, during which carboxylic acids bearing different alkyl lengths (isovaleric acid (IVA), hexanoic acid (HNA), octanoic acid (ONA), decanoic acid (DNA)) were used as anti-solvents. The longer alkyl lengths of carboxylic acids can render higher sucralose yield because the better flexibility can provide larger free void spaces with facilitation of emulsion shrinking, resulting in higher crystallization ratio and rate. Also, the ASC conditions have been optimized, based on which low aspect ratio (1.5585) and small particle size (15.755 μm) can be obtained using ONA as an anti-solvent. Based on single-crystal structure analysis, the ONA-treated product bearing relatively weaker O–H⋯O/C–H⋯Cl hydrogen bonds was adopted for further ultrasound-assisted ASC process. Interestingly, upon the intermittent sonication mode, the sucralose product with ultra-low aspect ratio (1.244) and larger crystal size (42.722 μm) can be obtained, which is attributed to the relatively stronger sp³-C–H⋯Cl⁰ hydrogen bonds on the {011} face than O–H⋯O bonds on the {101}/{110} faces. This work will provide a theoretical guide for the production of high-quality sucralose.