Development of New Method for Extraction of α-Zein from Corn Gluten Meal Using Different Solvents

A modified procedure for the extraction of alpha-zein from corn gluten meal was developed and compared against a commercial extraction method. The modification involved raising the concentration of alcohol in solvent and removing the precipitate by centrifugation. Five organic solvent mixtures were compared using the modified extraction procedure developed along with the reductant sodium bisulfite and NaOH. The modified procedure precipitated most of the non-alpha-zein protein solids by increasing the concentration of alcohol. The supernatant had alpha-zein-rich fraction, resulting in higher yield of alpha-zein than the commercial method when cold precipitated. The commercial extraction procedure had a zein yield of 23% and protein purity of 28% using 88% 2-propanol solvent. The three best solvents, 70% 2-propanol, 55% 2-propanol, and 70% ethanol, yielded approximate to 35% of zein at protein purity of 44% using the modified extraction procedure. Zeins extracted using the novel method were lighter in color than the commercial method. Densitometry scans of SDS-PAGE of alpha-zein-rich solids showed relatively large quantities of alpha-zein with apparent molecular weights of 19,000 and 22,000 Da. The alpha-zein-rich solids also had small amounts of delta-zein (10,000 Da) because it shares similar solubility properties to alpha-zein. A solvent mixture with 70% 2-propanol, 22.5% glycerol, and 7.5% water extracted significantly less zein (approximate to 33%) compared to all other solvents and had alpha-zein bands that differed in appearance and contained little to no delta-zein.