|Craig Jr, James|
Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 30, 2002
Publication Date: September 30, 2002
Interpretive Summary: Production of ethanol from corn has created a surplus of zein-rich byproducts, distillers' dried grains and corn gluten, which are increasingly difficult to sell but which must be sold to make ethanol plants viable. We have shown that zein extraction and sales can significantly reduce the overall cost of producing ethanol. Sale of extracted zein for non-feed products will enable U.S. corn producers to obtain and maintain higher return from the non-starch component of corn. Zein commercially extracted from corn gluten costs $10/lb and only a few tons are extracted each year; sales and use of greater amounts are inhibited by its cost. Commercialization of less expensive, larger scale, zein extraction facilities depends on demonstrating a low cost process and demonstration requires capital investment within the financial reach of prospective pioneers. This article reports that extracted corn can be separated from the liquid extract with inexpensive equipment, contrary to the conventional expectation and practice of the corn milling industry. Further development of the indicated method will enable production of market test quantities of zein at affordable cost.
Technical Abstract: Low cost extraction of maize protein using ethanol at the front end of a dry grind ethanol plant has been discussed in recent articles. Thorough recovery of (alcoholic) extract from the extracted maize is essential to make the process economical and, where the solid residues are to be subsequently fermented to ethanol, to prevent the ethanol from interfering with liquefaction enzymes or fermentation organisms. Three methods of separating liquid extract from the extracted corn particles were tried: packed bed displacement, centrifugation with rinsing and gravitational settling into water. Displacing extract (liquid) from a stationary bed of milled corn extract was too slow to be practical. This argues against the use of similar techniques based on stationary layers of extracted corn. Continuous centrifugation, with rinsing, was only effective at low feed rates, thus expensive. Settling into water was evaluated and appears to be a feasible method of extract separation, with low dilution of the extract and inexpensive equipment.