ARS | Publication request: Extraction and functional properties of non-zein proteins in corn germ from wet-milling

Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 15, 2012
Publication Date: March 12, 2012
Citation: Hojillaevangelist, M.P. 2012. Extraction and functional properties of non-zein proteins in corn germ from wet-milling. Journal of the American Oil Chemists' Society. 89(1): 167-174.

Interpretive Summary: In this research, we developed an inexpensive method to extract proteins from wet-milled corn germ and determined the chemical and functional properties of the recovered product. Nearly 500 million pounds of corn gluten feed (which contains corn germ) and 250 million pounds of corn germ meal/cake are produced per month in the United States, but they are utilized primarily by the animal feed industry. Our research provided fundamental data that would be useful in defining the conditions for optimal extraction and recovery of corn germ proteins and in identifying and developing novel uses for the protein. We calculated protein extraction yields, determined the solubility behavior, foaming properties, emulsifying properties, and water-holding capacities of the recovered germ protein extracts. We observed that wet germ protein extract was more soluble than finished germ protein at all pH values; however, the finished germ protein showed significantly better foaming and emulsifying properties and water-holding capacity. Based on these functionality results, the most promising avenues for utilization of corn germ proteins extracted by this method appear to be in foamed or whipped products, emulsions, and comminuted meat products. Developing new uses and markets for corn germ protein will enhance its value and generate additional income for corn growers.

Technical Abstract: This study was conducted to develop methods of extracting corn germ protein and characterize and identify potential applications of the recovered protein. Protein was extracted from both wet germ and finished (dried) germ using 0.1M NaCl as solvent. The method involved homogenization, stirring, centrifugation, dialysis and freeze-drying. Factors evaluated were temperature (40, 50, or 60°C) and presence of reducing or denaturing agents. The recovered protein was analyzed for proximate composition and functional properties. Extraction was done at 40°C because protein recovery was not improved by using higher temperatures. Addition of 2% SDS and 1% ß-mercaptoethanol to the solvent nearly doubled protein yield; but, SDS-PAGE indicated some protein denaturation. The recovered freeze-dried proteins from both germ samples were least soluble at pH 2.0-4.0, but solubility increased at higher pH values. Wet germ protein extract was more soluble than finished germ protein at all pH values; however, the finished germ protein showed much better foaming and emulsifying properties and water-holding capacity.