Characterization of Zein Extracted from Wet Distillers Grains

Abstract

Highlights Zein was extracted from wet distillers grains (WDG) with 55%, 70%, and 90% ethanol. Gelation was faster for zein extracted with 70% ethanol than with 55% and 90% ethanol. Alkaline extraction prevented gelation of zein samples. Defatting of WDG increased zein solubility, perhaps by preventing aggregation. Abstract. Coproducts of corn-to-ethanol processing remain potential sources of zein. Attempts to extract zein from dry-grind ethanol coproducts have been limited to distillers dried grains with solubles (DDGS). The aim of this project was to characterize the physicochemical and structural properties of zein extracted from wet distillers grains (WDG) in order to evaluate its quality and functionality. The effect of extraction conditions, including ethanol content of the solvent (55%, 70%, and 90% ethanol), use of NaOH, and defatting of WDG, on zein quality and functionality were investigated. Zein extracted with 70% ethanol showed physicochemical characteristics similar to zein extracted from corn gluten meal. Zein extractions with 55% ethanol were feasible but contained γ-zein and other impurities that affected functionality. Extractions with 90% ethanol contained carotenoids and other lipid materials that may have affected zein behavior. Alkaline extractions resulted in samples with higher protein content but lower solubility. Zein from alkaline extractions resisted particle aggregation and was more stable in solution. Alkaline extractions reduced the α-helix content of the samples and their γ-zein content, reducing viscosity and the tendency to gel. Defatting of WDG improved zein solubility, increased the α-helix content of extracted zein, and prevented aggregation. Extraction and utilization of zein from WDG would contribute to the control of plant operating costs and ease the environmental impact of dry-grind processes. High-quality zein from dry-grind coproducts would enable the development of novel foods and other industrial applications.