Continuous, high-throughput flash-synthesis of submicron food emulsions using a confined impinging jet mixer: effect of in situ turbulence, sonication, and small surfactants

Reproducible quality emulsions with high throughput are critical for a variety of specialized applications such as pharmaceutics and foods. In this work, we propose a simple and effective approach for producing highly stable, submicron sized, oil-in-water emulsions by high-shear, controlled turbulence in a confined impinging jet mixer using commercial-grade components and low molecular weight emulsifiers. Targeting the submicron range, food-grade oil-in-water emulsions in the 100 nm to 1 μm size range were produced by synergistically coupling multipass, jet-induced turbulence and ultrasonication effects to produce a throughput of up to 1.2 L/min. In addition, physiochemical effects of small molecule emulsifiers or surfactants and their formulations on drop breakup and stability were found to be important and were investigated to determine the optimal emulsifier deployment strategy. Other determining variables like magnitude and duration of local turbulence/energy dissipation and relative effects of competing process time scales were considered to explain the obtained results. The mixer was easy to fabricate and operate. Furthermore, several mixheads schemes were designed and tested for enhancement of local turbulence within the mixing volume. There is ample evidence that the confined turbulent impinging jet mixer can accelerate the development of specialized emulsion-based products/applications by providing a robust platform for synthesis of submicron and nano emulsions with precise properties at industrially relevant scales.