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ABSTRACT
Traditionally, zein is isolated and recovered from corn gluten meal (GCM) using aqueous alcohol as the solvent. Recovery of zein from this solvent is inconvenient and costly. Zein is insoluble in 100% ethanol at room temperature, but it is soluble at 120°C in ethanol. Absolute ethanol effectively extracted zein from CGM, distillers dried grains (DDG), and ground corn. Zein was extracted from CGM with absolute ethanol in a high-pressure reactor at 130°C. After extracting at 130°C for 45 min, the solution was pumped out of the extractor and allowed to cool. Upon cooling, the zein precipitated from solution. The precipitate was removed from the solution and air-dried, resulting in 14% recovery of the starting material. The recovered precipitate had an average protein content of >90% on a dry basis, accounting for [asymptotically =]20% of the CGM protein and recovered [asymptotically =]35% of its zein. No differences were seen in the amount of zein extracted from CGM samples that were hand-collected off the dewatering screen and gently dried, versus commercial CGM samples. The commercial CGM did produce a greater amount of solubles. The extraction procedure also worked at temperatures as low as 90°C. The lower temperature did produce lower yields of extracted zein. The zein extracted at the lower temperatures was less brown, but zein extracted at either temperature was almost fully soluble in traditional zein solvents.
Cereal Chem. 83(5):565-568
Zein was first extracted by Gorham (1821) from whole corn using aqueous ethanol. Osborne (1891) was granted the first patent for a commercial method for zein extraction. Commercial production of zein was not achieved until 1938 when the Corn Products Refining Company built a small pilot plant (Anon. 1939). A much larger plant was built by Corn Products Refining Company in 1943 (Anon. 1944). These plants recovered zein by spraying the aqueous alcohol zein solution into cold moving water (Horesi et al 1941). Today, zein is recovered from the aqueous alcohol solvent by chilling the extract to -10 to -20°C (Lawton 2002). Zein precipitates from aqueous alcohols at these low temperatures. Spray drying or vacuum drying have been suggested as methods to recover zein from aqueous alcohol solutions (Shukla and Cheryan 2001; McInnis and Tang 2003).
The problem with using aqueous ethanol is...