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

Abstract

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% b-mercaptoethanol to the solvent nearly doubled protein yield; but, SDS-PAGE indicated some protein denaturation. The recovered freezedried 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.

Improved Solubility and Emulsification of Wet‐Milled Corn Germ Protein Recovered by Ultrafiltration–Diafiltration

“…Wet and dried corn germ from wet-milling were provided by Aventine Renewable Energy Inc. (Pekin, IL). In our previous work [9] we defined wet germ as that from any stream before the final drying step while dried germ was the material set aside after the last drying step. Germ samples were frozen in polypropylene containers, but were allowed to warm up to room temperature before being used for experiments.…”

“…Corn germ was first ground to a particle size of ca. 0.35 mm (42 mesh) by using a Fritsch Rotor-Speed Mill (VDE 0,530, Idar-Oberstein, Germany) equipped with a 0.6 mm screen and then defatted with hexane as described in our previous work [9]. Our earlier method to extract nonzein corn germ proteins [9], which used 0.1 M NaCl at 50°C, homogenization, centrifugation, filtration, dialysis, and freeze-drying, was designated as the baseline method for comparison.…”

“…0.35 mm (42 mesh) by using a Fritsch Rotor-Speed Mill (VDE 0,530, Idar-Oberstein, Germany) equipped with a 0.6 mm screen and then defatted with hexane as described in our previous work [9]. Our earlier method to extract nonzein corn germ proteins [9], which used 0.1 M NaCl at 50°C, homogenization, centrifugation, filtration, dialysis, and freeze-drying, was designated as the baseline method for comparison. In the present study, the UFDF method to extract and recover the corn germ protein was based on the method described by Hojilla-Evangelista et al [16] with minor modifications.…”

“…Recently, we attempted to recover protein from wetmilled corn germ using a saline-based extraction method [9] that was developed from knowledge of albumins and globulins as major soluble protein classes in corn germ. Protein recovery and purity (both at 30 %) were low.…”

Corn Lecithin for Injection from Deoiled Corn Germ: Extraction, Composition, and Emulsifying Properties

“…[1,2] The production and consumption of corn oil have increased in recent years, mainly because of its health benefits and flavor. Although the germ in normal dent corn is only 11% of the total weight, its crude fat content (30-50%, dry basis) makes it the principal source of edible corn oil.…”