463234 Development of an Integrated Process for Sustainable Production of Biodiesel and Plant Protein Isolates from Underutilized Feedstock

Wednesday, November 16, 2016: 1:14 PM
Union Square 17 & 18 (Hilton San Francisco Union Square)
Solmaz Tabtabaei and Levente L. Diosady, Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, ON, Canada

“Food or Fuel” is an international concern about the use of agricultural land for biofuel production, which results in higher food prices and adversely affects the living standards of poor people. Consequently, it is essential to find compromises that meet the demand for both food and green transportation fuels. Yellow mustard is a Canadian food crop that is a viable source of both oil and protein. At present neither of these valuable components are utilized as most of the seed is now only used as condiment. The proteins have a well-balanced amino acid distribution making them potentially useful as a food ingredient, and the inedible oil, which is high in erucic acid, is desirable in biodiesel due to its superior lubricating properties. In this study, an integrated process was developed to produce food-grade protein isolates, free of solvent contact/residues, and fuel-grade biodiesel from dehulled yellow mustard flour. This process makes novel contributions to the link between energy, food and the environment.

The aqueous extraction of proteins form mustard flour was started by contacting the flour with water at room temperature and alkaline pH 11 followed by centrifugation. The protein was recovered in the form of protein-rich skim fraction with minimal protein damage, while the oil was released as a separate fraction and tied up in a very stable oil-in-water emulsion. The protein-rich skim fraction was further concentrated and purified by membrane processing followed by isoelectric precipitation to produce two high quality food-grade protein isolates: isoelectric precipitated protein isolate (PPI) and acid soluble protein isolate (SPI). The PPI and SPI with desired functionalities had 96.0 and 83.5% protein content on a moisture and oil free basis, respectively.

The underutilized oil-rich emulsion fraction was characterized where its remarkable stability was due to the presence of protein emulsifiers of high molecular weight along with the mixed phospholipid-oleosin layer. The emulsion was successfully destabilized by a novel chemical approach where the organic solvents including isopropyl alcohol (IPA), tetrahydrofuran (THF) or dioxane were used to solubilize the emulsion to produce a single-phase oil-solvent-water miscella. The ternary phase diagrams of THF/oil/water, dioxane/oil/water, and IPA/oil/water were prepared, and the solubility of the oil in these organic solvents in the presence of water was determined. The application of ternary phase diagrams resulted in the development of three-stage destabilization process at which all of the oil was successfully recovered from the emulsion into the miscella. The oil-solvent-water miscella was dehydrated in the next phase by adsorption over zeolite 4A using either batch or continuous fixed-bed systems. The dehydrated miscella was reacted with methanol in a single-phase base-catalyzed transmethylation process with high yields (99.4%) to fatty acid methyl esters (FAME). The resulting FAME satisfied the international standards for use as biodiesel fuel.

Approximately 69% of the protein originally in the flour was recovered as high-quality protein products and over 62% of the oil in the flour was recovered as standard biodiesel through this integrated process. The preliminary economic analysis showed an overall positive margin. The application of this processing approach could help increase Canadian production of both food ingredients and biofuel, without impacting the cost of edible oils, as very large areas of Canada can be readily converted to mustard production.


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