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United States Department of Agriculture

Agricultural Research Service

Title: Zein Decolorization Methods

item Sessa, David
item Eller, Fred
item Lawton Jr, John

Submitted to: Corn Utilization Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: September 26, 2002
Publication Date: June 3, 2002

Technical Abstract: The yellow color corn and corn processing coproducts is due to xanthophylls and carotenes which possess nutraceutical value. Colorless zein commands a premium price. Our objective was to devise methods for decolorizing zein. Methods investigated include: supercritical CO2 extraction of zein with alcohol entrainers; ultrafiltration/diafiltration of ethanolic solutions of zein on a tangential flow system; partitioning of zein ethanolic solutions with toluene; column chromatography of ethanolic solutions of zein on Sephadex LH-60; batch treatment of ethanolic zein solutions with activated charcoal. Color removal assessed by dissolving either a zein control or decolorized zein in glacial acetic acid, filtration of each solution through glass fiber filters, preparation of a series of dilutions and reading absorbances of each dilution at 448nm. Comparative logarithmic regressions of each series of control zein and decolorized zein dilutions were used to determine degree of color removal. Results were compared with dilutions of a commercial white zein product. Results show that the commercial white zein product and the zein solutions partitioned with toluene possessed similar degree of color removal which was least for decolorization methods investigated. Whereas, the most complete removal was achieved by batch treatment with activated charcoal. However, recovered yield was lowest of all other methods evaluated. Supercritical CO2 extraction of zein wetted with 15% ethanol entrainer for 15 minutes at 10,000 psi and 70 degrees C decolorized zein to a similar extent as either the column chromatographic method with Sephadex LH-60 or diafiltration of zein ethanolic solutions ultrafiltered through 5000 molecular weight cutoff membranes. The column chromatographic method as well as the ultrafiltration/diafiltration method each gave excellent recovery of decolorized zein product with the added benefit of removing a low molecular weight protein contaminant from commercial zein. The supercritical CO2 method - the method of choice - had the advantage of no need to spray-dry the final product and did not require the copious aqueous ethanol volumes needed for color removal by the other methods. Subcritical propane extraction of zein, where propane has lower polarity than that of supercritical CO2, currently being investigated, may prove to be the most beneficial method for decolorizing zein.

Last Modified: 4/22/2015
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