Extraction of zein from corn co-products

Abstract

<p>The current commercial zein protein extraction system yields low product recovery; we discovered ways to improve extraction efficiency and recovery. We began with a new way to increase the extraction of zein from (DDGS). The first aim was to fractionate extracted protein, including zein from DDGS. A new solvent system for zein was designed increase zein extraction and to use a biodiesel co-product rather than water in the process of extracting zein. This solvent was a ternary solvent using either 2-propanol or ethanol with water and glycerol. Four solvents were chosen for extraction: 70% (v/v) aqueous ethanol; 55% (w/w) 2-propanol; 40% (v/v/v) aqueous ethanol; 45% glycerol, and 15% water; and 40% (v/v/v) aqueous 2-propanol, 45% glycerol, and 15% water. Both the ethanol and 2-propanol solvent systems extracted modest amounts of zein, but the solvents with added glycerol extracted much less. It was apparent that the new solvent system was not performing as well as the solvents that are currently used to extract zein from DDGS.</p> <p>A new approach for extracting zein from DDGS was devised based upon one used for extraction from corn gluten meal (CGM) (Wu et al 1997, Carter and Reck 1970). CGM is a high protein corn wet milling co-product from which zein has been extracted commercially. Zein extraction from CGM has been plagued by low extraction efficiency of alpha-zein (</p> <p>Based on zein yields from CGM, three solvents were chosen for zein extraction from DDGS. The solvents were 88% (w/w) aqueous 2-propanol, 70% (w/w) aqueous 2-propanol, and 70% (v/v) aqueous ethanol. Two treatment methods were compared based on the commercial zein extraction method from CGM and the other modified method was devised in our lab from the previous CGM extraction. The pretreatment of DDGS (particle size reduction and enzyme treatment) was explored. The particle size reduction was to determine if increased surface area of the DDGS could increase zein extraction. The enzyme treatment was a combination of cellulase and pectinase hydrolysis prior to the zein extraction. The hydrolysis was to observe if polysaccharides impedes zein extraction due to a complex solute matrix and thereby reducing zein extractability from DDGS. The enzyme hydrolysis and the particle size had no effect on the zein extraction. The modified method was able to extract about 4x as much alpha-zein as the commercial method. The zein from the modified method also was able to produce functional zein comparable to zein extracted from CGM.</p>