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United States Department of Agriculture

Agricultural Research Service

Title: Thermal Gradient Fractionation of Glyceride Mixtures under Supercritical Fluid Conditions

Authors
item King, Jerry
item Sahle Demessie, Endalkachew
item Temelli, Feral - UNIV OF ALBERTA, CANADA
item Teel, Jeffrey

Submitted to: Journal of Supercritical Fluids
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 2, 1996
Publication Date: N/A

Interpretive Summary: Vegetable oils, such as soybean oil, can be converted to a number of products that find use in the food, cosmetic, and lubrication industries. Using a process called glycerolysis, vegetable oils are transformed into mixtures containing high value components called monoglycerides, which are the major consitutent of emulsifiers used as food additives in baking and food compounding. Enriching the glyceride-containing mixtures with respect to their monoglyceride content calls for a process that maintains but does not degrade the food emulsifier composition and that is environmentally acceptable. Using carbon dioxide as a fractionating agent, we have developed a process that will enrich the monoglyceride component in naturally derived emulsifier compositions from vegetable oil feedstocks. The resultant high monoglyceride content, coupled with the color attribute, offers the end user a superior product for incorporation into food compositions, free of any harmful chemicals.

Technical Abstract: Supercritical CO2 was used to fractionate a mixture of monoacylglycerides (MAGs), diacylgylcerides (DAGs) and triacylglycerides (TAGs) using an eight-foot packed column that was kept under thermal gradient conditions and operated semi continuously. Fractionation of the glyceride mixtures was affected by both their solubility in CO2 and respective vapor pressure enhancement. The feed material used, approximating a feed stream used in the industrial enrichment of MAGs, was composed of 48.7wt% MAG, 46.3 wt% DAG, and 5 wt% TAG having main acyl chain compositions of 6 wt% C16:0, 23 wt% C18:0 and 59 wt% C18:1. The resultant top product had MAG concentrations as high as 90 wt% and no TAG, which is comparable to that produced by molecular distillation. Increasing column pressure from 172 bars to 344 bar, or density of CO2 from 420 to 720 kg/m3, increased yields of the top product. However, with those increases, the supercritical fluid became less selective, with the MAG concentration decreasing from 84 wt% to 56 wt%. At 207 bars, a linear temperature gradient varying from 65 C to 95 C, gave the best selectivity when compared to other temperature gradient schemes. Increasing the CO2 flux from 1.8 to 10.3 g/min/cm2 resulted in little change in MAG concentration, but the top product yield decreased from 14.4 g/kgCO2 to 2.3 g/kgCO2. As the MAGs' concentrations in the feed mixture increased from 48.7 wt% to 63 wt%, the MAGs' concentration in the top product (at 207 bars, 65-95oC) increased from 79.4 wt% to 86 wt%.

Last Modified: 7/25/2014
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