Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/25/2004
Publication Date: 6/1/2004
Citation: Parris, N., Singh, V., Johnston, D. 2004. Isolation of zeins from enzymatically milled corn. Meeting Abstract. Corn Utilization & Technology Conference, June 7-9, 2004, Indianapolis, IN. p.41.
Technical Abstract: Corn wet milling is the principal method currently used to separate corn into starch, germ, fiber and proteinaceous fractions. About one third of the starch produced is used for food or industrial applications, one third is converted to sweetener, and a third is fermented to fuel ethanol. A major problem with this process however is the use of sulfites. Sulfites add considerable cost to the process and creates safety and health concerns while limiting the use of many protein co-products. A new modified process has been developed for dry grind ethanol production called enzymatic milling (E-Mill) based on wet milling work done previously (1). The E-Mill process, allows recovery of germ, coarse fiber and endosperm fiber as valuable co-products at the beginning of the dry grind ethanol process prior to fermentation. After fermentation a high protein (~58%) co-product called modified DDGS is produced, which can be used for zein extraction. In this study we examined the composition of zeins isolated from high protein coproduct produced from E-Mill dry grind processes. We compared the tensile properties of films prepared from these isolates with films prepared from commercially available zein F-4000. Zeins were extracted from the modified DDGS samples using 70% ethanol at 55°C for 2h. Extracts were diluted with water to 40% ethanol and the zeins were allowed to precipitate from solution overnight at 4°C. The precipitate was recovered after centrifuging at 9,000 x g, 4°C, 20 min. Analysis of the precipitate by SDS-PAGE indicated that the samples contained a mixture of zeins, covalently linked polymers and higher molecular weight aggregates. In addition to Alpha zein (22kDa), the principal prolamine, sulfur rich Beta and Gamma zeins (18kDa, 27 kDa) were also present in the precipitate. Aggregation and the presence of the minor zeins are consistent with the protein composition of the zein isolate extracted from dry-milled corn (2). In general, zeins extracted from the modified DDGS samples exhibited good film forming properties. To measure mechanical properties of the sample, the extraction procedure was repeated. A total of 0.8g sample and 0.2g poly (ethylene glycol) average MW ca 400 was dissolved in 30 mL 70% ethanol. The mixture was heated with stirring at 60C for 10 min. Solutions were cast in polystyrene Petri dishes and dried in a vacuum oven adjusted to 10 inches mercury at 50°C. Mechanical properties and appearance of these zein films were comparable to those prepared from zein F-4000. Results of this study should provide useful information to all corn utilization researchers and to scientists and engineers involved in the preparation of biodegradable zein films and coatings.