Characterization of protein extracted from flaked, defatted, whole corn by the sequential extraction process

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Abstract
An investigation was conducted to identify and characterize protein extracted by 45% ethanol:55% 0.1 M NaOH from flaked, defatted, undegermed corn (Zea mays L.) during Sequential Extraction Processing (SEP). This new approach to corn milling, SEP, recycles the ethanol produced from the fermentation of cornstarch to upstream steps of protein extraction and the simultaneous extraction of corn oil and dehydration of the ethanol. About 10% of the protein was extracted by ethanol during counter‐current‐percolation oil extraction. Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) and amino acid analysis identified this protein as zein. Nearly 65% of the total protein was recovered by the process in the protein extraction step from soft dent corn (Pioneer 3377), medium‐hard dent corn (Pioneer 3732) and high‐lysine corn. The freeze‐dried solids of the ethanol/alkali extracts from these corn hybrids contained about 80% crude protein (db). The amino acids were present in quantities similar to those in whole corn and markedly higher than those in corn gluten meal. These results indicate that SEP produces high‐quality protein suitable for food and industrial uses.