Biodiesel Feedstock from Emulsions Produced by Aqueous Processing of Yellow Mustard

The multi-stage treatment of stable oil-in-water emulsions produced during non-enzymatic aqueous processing of dehulled yellow mustard flour with cyclic ethers [tetrahydrofuran (THF) and 1,4-dioxane] was investigated to produce a single-phase oil-solvent-water miscella suitable for biodiesel production. While the single-stage treatment of yellow mustard emulsion recovered 97 % and 95 % of the oil by using 4:1 THF:oil and 9:1 dioxane:oil weight ratios, respectively, miscella phases containing more than 7 % water formed, which made them unsuitable as biodiesel feedstock. Multi-stage treatments of the emulsion using lower THF:oil and dioxane:oil weight ratios were further developed to produce oil-solvent-water miscella phases with low water content. While three-stage extraction of emulsions using 0.5:1, 1:1, 1.5:1, and 2:1 dioxane:oil weight ratios did not destabilize the emulsion, three-stage extraction using 0.5:1 and 0.75:1 THF:oil weight ratios effectively recovered over 97 % of the oil, resulting in the production of oil-rich miscella phases containing only 1 % and 1.5 % water, respectively. These miscella phases were analyzed for free fatty acid and phosphorus contents and proved to be excellent feedstocks for the preparation of high-purity methyl esters through single-phase base-catalyzed transmethylation.