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Extraction and Functional Properties of Non-Zein Proteins in Corn Germ from Wet-Milling

Hojilla-Evangelista, Mila P.
journal of the American Oil Chemists' Society 2012 v.89 no.1 pp. 167-174
centrifugation, corn germ, denaturation, dialysis, emulsifying properties, foaming, freeze drying, homogenization, mixing, pH, polyacrylamide gel electrophoresis, proteins, proximate composition, sodium chloride, solubility, temperature, water holding capacity, wet milling
This study was conducted to evaluate the extractability of wet-milled corn germ protein, characterize the recovered protein and identify its potential applications. Protein was extracted from both wet germ and finished (dried) germ using 0.1 M NaCl as solvent. The method involved homogenization, stirring, centrifugation, dialysis and freeze-drying. Factors evaluated were temperature (40, 50, or 60 °C) and the presence of reducing or denaturing agents. The recovered protein was analyzed for proximate composition and functional properties. Protein recovery was greater from wet germ. For both germ samples, protein recovery was not improved by using higher temperatures; thus, subsequent extractions were done at 40 °C. Addition of 2% SDS and 1% β-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.