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Title:Characterization of zein extracted from beer solids, a coproduct of dry-grind ethanol
Author(s):Guardiola, Lia Vanessa
Director of Research:Padua, Graciela Wild
Doctoral Committee Chair(s):Feng, Hao
Doctoral Committee Member(s):Engeseth, Nicki Jane; Lee, Youngsoo
Department / Program:Food Science & Human Nutrition
Discipline:Food Science & Human Nutrition
Degree Granting Institution:University of Illinois at Urbana-Champaign
Dry grind ethanol
Abstract:Zein, the prolamine of corn, has been proposed for different food applications: as coating material for flavor encapsulation, in moisture barrier films, as chewing gum base. Most recently, it has been explored in biomedical applications as tissue scaffolding, to enhance cell spreading and viability. Coproducts of corn-to-ethanol processing remain potential sources of zein. Distillers’ wet grains (DWG) a coproduct of dry grind ethanol contain about 40% (db) protein, where 50% of the protein is zein. Attempts to extract zein from coproducts have been limited to distillers’ dried grains with solubles (DDGS), but products from this process have not been fully characterized. In this work, DWG from dry-grind ethanol operations were used to extract zein. The aim of this project was to characterize selected physicochemical and molecular properties of the obtained zein to determine its quality and investigate its functionality. Zein was also further developed into a zein-based foam as a possible new application. The effect of extraction conditions: ethanol content of the solvent (55, 70 and 90% ethanol), pH, processing temperature and time, on zein quality and functionality parameters was evaluated. NaOH was used to modify the pH of extraction solvent. Alkaline extractions resulted in samples with higher protein content, although, of lower solubility. Additionally, alkaline extraction, reduced or eliminated g-zein from the zein profile. Moreover, zein of alkaline extraction resisted particle aggregation and consequently, was more stable in solution. Alkaline extractions reduced the a-helix content of the samples, which may have contributed to the samples’ lower solubility. Alkaline samples had a nearly Newtonian behavior and a predominantly viscous behavior. On the contrary, non-alkaline extraction samples had a shear thinning behavior and over time developed elastic behavior. Zein extractions with 55% ethanol are feasible; however, extractions of small protein fractions, and other impurities can occur. Extractions made with 90% ethanol did not follow any specific trend, oil and carotenoids extracted along with proteins may have affected their behavior. Removal of zein impurities with hexane improved zein solubility. Furthermore, defatting of DWG increased the a-helix content of the samples and prevented aggregation. Extractions made with 70% ethanol resembled more closely the expected characteristics and behavior of commercial samples extracted from CGM. Extraction and utilization of zein from DWG would contribute to control plant operation costs and ease the environmental impact of this process. Zein has the ability to form glossy, flexible and hydrophobic coatings, these properties have led zein to be proposed for a number of applications: in controlled release, as a coating material, in biodegradable films, as a wall material for microencapsulation, and more recently as a biomedical material for tissue scaffolding. This investigation focused on studying zein as a potential base for foam development, where zein in concentrated solutions was precipitated into resins, which were expanded into foams by microwave energy. It was found that foam cell formation, expansion and organization depended on the amount of ethanol (%) used in the process. Moreover, residual solvent content in the foams affected foam formation. Extraction and marketing of zein from DWG would contribute to offset corn-to- ethanol plant operation costs and reduce their environmental impact. Moreover, a high quality zein from dry grind ethanol coproducts would enable the food industry to develop a number of novel food applications.
Issue Date:2019-01-09
Rights Information:Copyright 2019 Lia Guardiola
Date Available in IDEALS:2019-08-23
Date Deposited:2019-05

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