Nanoparticle formation of β-carotene by mixing supercritical carbon dioxide antisolvent with liquefied dimethyl ether feed solution using swirl mixer

Abstract

The production of β-carotene nanoparticles using non-toxic and environmentally-friendly liquefied dimethyl ether (DME) via a supercritical antisolvent (SAS) process, which produces no residue, is a major challenge in food processes. Preparations of nanoparticles have previously been conducted with toxic organic feed solvents. In this work, β-carotene was micronized with two feed solutions, liquefied DME and ethyl acetate, using a swirl mixer mixing in a turbulent field by the SAS method for comparison. The effects of operating pressure, temperature, and solution flow rate were investigated on the size of nanoparticles. Field-emission-scanning electron microscopy (FE-SEM) images showed that dispersed β-carotene nanoparticles, 43.9 nm in size, were successfully prepared at 40 °C and 8 MPa, and no residual DME was present in the nanoparticles. Using an ethyl acetate solution to precipitate β-carotene at 40 °C and 10 MPa and successfully obtained nanoparticles 62.12 nm in size. Compared to the previous study (12 MPa, normal nozzle), the smallest β-carotene particles precipitated from the optimal conditions of DME and ethyl acetate, respectively, were obtained at lower pressures and smaller particles with the swirl mixer. X-ray diffraction (XRD) and differential thermal analysis (DTA) confirmed that the obtained nanoparticles were amorphous. By contrast, residual ethyl acetate solution was present in the nanoparticles precipitated from ethyl acetate; this phenomenon was confirmed using Fourier transform infrared spectroscopy (FT-IR) and gas chromatography-mass spectrometry (GC–MS).