(93d) Extraction of Complex Lipids from Aqueous Streams Using near-Critical Dimethylether

Dimethylether is an ideal solvent for processing lipids from natural materials. It is an effective solvent for many polar lipids as well as neutral lipids, is non-toxic, and is not a greenhouse gas. It is gaseous in its natural state so can be removed easily and virtually completely from residual product streams. Dimethylether is also partially miscible with water so that processing of materials containing water is possible without needing to dry the materials first.

This paper describes a process for extraction of lipids from aqueous feed streams. The aqueous feed stream is contacted with liquid dimethylether in co-current flow through a static in-line mixer. A separation step follows in which lipids dissolved in the dimethylether phase are removed from the top of the vessel. Non-soluble solids such as proteins and sugars, and any excess water, are recovered in a raffinate phase from the bottom of the vessel. The extract phase is depressurised to vapourise the dimethylether allowing recovery of the lipid extract and recycling of the dimethylether. This process can be operated continuously.

Examples are given for extraction of selected dairy and egg yolk process streams. Extracted lipids include phospholipids, gangliosides, and sphingolipids. Residual proteins in the raffinate stream are denatured to a varying extent depending on the processing conditions.

Results are given for measurements of dimethylether water phase equilibria, and modelling using the Wong-Sandler mixing rules with the Peng-Robinson equation of state.