ARS | Publication request: Improved isolation of zein from corn gluten meal using acetic acid as solvent

Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 2, 2007
Publication Date: March 1, 2008
Citation: Selling, G.W., Woods, K.K. 2008. Improved isolation of zein from corn gluten meal using acetic acid as solvent. Cereal Chemistry. 85(2):202¿206.

Interpretive Summary: Zein, one of the potential major co-products of the bio-ethanol industry, was historically a high-value raw material that was used in the coatings and fibers industries. Over time it was replaced by various petroleum-based products. For zein to be again used in these and other markets, improved methods for its isolation are needed to drive down the cost of zein. The method reported here utilizes acetic acid, a chemical readily produced from renewable resources, to remove zein from various corn products. In a laboratory setting, acetic acid removes zein from these sources faster and at lower temperatures when compared with those procedures described in either the open literature or the patent literature. The zein produced by acetic acid extraction is of slightly lower quality than that produced by traditional routes. However, the quality is such that zein-based products, such as films and fibers, can be made of reasonable quality. This research will benefit corn producers and the bio-ethanol industry by providing an improved method for isolating zein which can then be used to provide higher value co-products.

Technical Abstract: To develop new uses for corn zein, an improved means of isolating zein is needed. We have evaluated the ability of acetic acid to remove zein from corn gluten meal, distillers dried grains and ground corn. Acetic acid removed zein more quickly, at lower temperatures and in higher yields when compared with alcoholic solvents. After 60 min at 25 deg C, approximately 50% of the zein in corn gluten meal was removed. A step change in yield, from 43 to 50%, occurs as the extraction temperature is increased from 40 to 55 deg C after mixing for 30 minutes at 25% solids. The protein composition of the zein removed from corn gluten meal using acetic acid is very similar to that of commercial zein by SDS-PAGE. The zein obtained from corn gluten meal using acetic acid had higher amounts of fatty acids and esters by IR analysis, leading to lower protein content. Films made from zein extracted from corn gluten meal using acetic acid had lower tensile strength (~ 60% lower) than films produced from commercial zein. Fibers having very small diameter (0.4 ¿ 1.6 um) can be produced by electrospinning using the acetic acid solution obtained after corn gluten meal extraction.