EFFICIENT PROCEDURE FOR EXTRACTING MAIZE AND SORGHUM KERNEL PROTEINS REVEALS HIGHER PROLAMIN CONTENTS THAN THE CONVENTIONAL METHOD

A new method to separate maize proteins into zein (prolamin) and nonze in classes was used to quantitatively measure the prolamins (zein and kafirin) and nonprolamins in five maize and sorghum genotypes. Some 90 -95% of protein was extracted using a pH 10 buffer containing 1% sodiu m dodecyl sulfate and 2% 2-mercaptoethanol. Ethanol or t-butanol was a dded to the maize and sorghum extracts at 70 or 60%, respectively, to precipitate nonprolamin proteins; those remaining in solution were pro lamins. The amount of protein in these fractions was compared to that obtained with the conventional Landry-Moureaux method which uses aqueo us alcohol plus 0.6% 2-mercaptoethanol as the extraction solvent. Usin g this new method, zein contents of 50-60% of total protein were found for maize whole grain flours, with 62-74% zein for endosperm alone. K afirin contents were 68-73% in sorghum whole grain flours, and 77-82% in sorghum endosperm. Prolamin and nonprolamin fractions were judged t o be pure based on SDS-PAGE. Zein contents determined by the new metho d were between 5-12% higher than those obtained by the conventional pr ocedure; kafirin contents were 12-22% higher. This new method provides a highly reproducible, accurate procedure for determining the content of prolamin and nonprolamin proteins. Yet it is simpler and faster th an the conventional fractionation method.