Author
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Wolf, Walter |
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Lawton Jr, John |
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Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 5/20/1997 Publication Date: N/A Citation: N/A Interpretive Summary: The need to rely more on renewable resources has led to the increased fermentation of corn to produce alcohol for use as a fuel. A major co- product of alcohol production is the unfermented corn residue, corn distillers' grains with solubles, which is dried and used as a livestock feed. About one-half of the protein in corn is zein, an unusual protein with waterproofing properties, that may be useful in making water-sensitiv biodegradable plastics more resistant to moisture. This research showed that zein is still present in corn distillers' grains with solubles having survived the cooking, fermentation, distillating and drying steps used in making alcohol. Corn distillers' grains with solubles may, therefore, be useful as an additive to make biodegradable plastics more waterproof and thus more competitive with petroleum derived products which are slow to degrade after their useful lifetime. Technical Abstract: Corn distillers'grains with solubles (CDGS), the major co-product of fermentation of corn to produce ethanol, was extracted with 0.1 M NaOH:0.1% dithiothreitol (DTT):0.5% sodium dodecylsulfate yielding 35% of the total nitrogen and about 25% of the protein nitrogen. Gel electrophoresis revealed that the extractable proteins contained zein plus other proteins similar to the extractable proteins from corn flour. Although difficult to extract, the proteins from the fermentation co-products appeared undegraded and apparently survived gelatinization, fermentation, distillation and drying during the production of ethanol. Extraction of CDGS with 60% ethanol at 60 deg C yielded 1.5-3.9% of crude zein. When the ethanol contained DTT, yields of crude zein were increased to 3.2-6.6%. Protein contents of the crude zeins were only 37-57% indicating that lipids and pigments were co-extracted with the ethanol. Gel electrophoresis showed that the protein fractions extracted by ethanol contained primarily alpha-zein whereas the proteins extracted by ethanol + DTT contained alpha-zein plus beta- and gamma-zeins. Further confirmation of the presence of zein in the crude prolamin preparations was obtained by amino acid analyses. The amino acid compositions of the crude zeins paralleled those of commercial zein and alpha-zein. |
