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

¹Graduate student, Department of Food Science and Human Nutrition, Iowa State University, Ames, IA 50011. ²Assistant professor, Department of Food Science and Human Nutrition, Iowa State University, Ames, IA 50011. ³Corresponding author. Phone: (515) 294-8681. Fax: (515) 294-8181. E-mail: lamsal@iastate.edu

A modified procedure for the extraction of α-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-α-zein protein solids by increasing the concentration of alcohol. The supernatant had α-zein-rich fraction, resulting in higher yield of α-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 ≈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 α-zein-rich solids showed relatively large quantities of α-zein with apparent molecular weights of 19,000 and 22,000 Da. The α-zein-rich solids also had small amounts of δ-zein (10,000 Da) because it shares similar solubility properties to α-zein. A solvent mixture with 70% 2-propanol, 22.5% glycerol, and 7.5% water extracted significantly less zein (≈33%) compared to all other solvents and had α-zein bands that differed in appearance and contained little to no δ-zein.