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Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 4/30/1998 Publication Date: N/A Citation: N/A Interpretive Summary: Most fuel alcohol produced in the U.S. comes from fermentation of starch obtained from the wet milling of corn. The process also produces several coproducts including corn fiber. Currently, corn fiber is combined with steep water and fermentation liquids to make corn gluten animal feed. Increased fuel alcohol production will necessitate new uses of corn fiber. Corn gum is one potential new product. In this research, we examined several methods to extract corn gum from corn fiber. These methods included use of limewater, ammonia water, and dilute alkali solutions. The optimal method found was extraction with alkali solutions, treatment with lime to remove impurities, and finally recovery of the insoluble corn gum from alcohol treated solutions. This corn gum forms clear, viscous solutions when dissolved in water and could be used as a food thickener, adhesive, or in biodegradable films. In addition, the residual corn fiber could still be used as an improved animal feed. Production of corn gum is simple and compatible with wet milling operations. This gum is potentially a valuable coproduct and could significantly lower the overall costs of producing fuel alcohol from corn. Technical Abstract: The wet milling of corn converts the hull layer into the byproduct known as corn fiber, which is used to make corn gluten animal feed. Increased fuel ethanol production from corn will necessitate other uses of corn fiber. More than 30% of the corn fiber is in the form of a xylan (CFX). CFX forms viscous solutions and has gum-like properties that suggest it may have potential uses in food products, thickening agents, or biofilms. Various procedures were examined for rapid extraction of CFX from corn fiber to obtain a purified material. Using 2% calcium hydroxide and precipitation with ethanol yielded a relatively pure CFX material but required long extraction times (16-20 h) and produced a hard, insoluble fiber residue. Extractions with 15% ammonium hydroxide yielded a rather impure CFX material and required similar long extraction times. The impurities could be removed by treating potassium hydroxide dissolved CFX with calcium hydroxide prior to ethanol precipitation; however, overall recoveries were very low (5%). Extraction with potassium hydroxide solutions were attempted using various combinations of time, temperature, and concentrations. Extraction with 2% potassium hydroxide at 70 deg C for 4-6 h, coupled with calcium hydroxide treatment of the dissolved CFX, produced a highly pure CFX material composed of 94% neutral sugars, 7% hexuronic acids, and 3% protein. The overall CFX yields were good (15%), and the residual fiber material still appeared physically suitable for use as a feed or for other uses. |
