Submitted to: Bioresource Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/30/2007
Publication Date: 1/29/2008
Citation: Sessa, D.J., Palmquist, D.E. 2008. Effect of heat on the adsorption capacity of an activated carbon for decolorizing/deodorizing yellow zein. Bioresource Technology. 99(14):6360-6364. Interpretive Summary: Corn zein, a co-product of the ethanol industry, is a predominant corn protein that has numerous potential industrial uses. A major deterrent for its useage is its yellow color and off-odor. Activated carbon will decolorize and deodorize corn zein, but, because activated carbon adsorbs the protein as well as the color and odor components; low yields of a white, odorless zein product are recovered in the process. A statistical evaluation of the finding characterics of protein, color and odor components with temperature demonstrated that a specific temperature of 55 deg C impacted positively on the adsorption capacity of activated carbon for binding the color/odor components with no increases in protein adsorptions. This basic information for decolorizing, deodorizing corn zein to generate a white odorless zein product will not only benefit the farmer and ethanol industry, but also will further zein's useage in the medical, pharmaceutical, and cosmetic fields, applications as a paper coating, packaging material and biodegradable chewing gum base where a decolorized, deodorized zein product is now needed.
Technical Abstract: The Freundlich model was evaluated for use to assess the effect of heat on the adsorption capacity of an activated carbon for decolorizing/deodorizing corn zein. Because zein protein and its color/odor components are all adsorbed by activated carbon, a method to monitor their removal was needed. Yellow color is due to xanthophylls; a contributor to off-odor is diferuloylputrescine. The off-odor component absorbs ultraviolet (UV) light at about 325nm and its removal coincides with removal of yellow color. A spectrophotometric method based on UV absorbances 280nm for protein and 325nm for the off-odor component was used to monitor their adsorptions onto activated carbon. Equilibrium studies were performed over temperature range from 25 deg C to 60 deg C for zein dissolved in 70% aqueous ethanol where runs made at 55 deg C gave significantly higher adsorptions of color/odor components than did protein.