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Recovery of Fiber in the Corn Dry-Grind Ethanol Process: A Feedstock for Valuable Coproducts

¹Visiting assistant professor and professor, Department of Agricultural Engineering, University of Illinois, Urbana, IL 61801. ²Corresponding author. E-mail: vsingh@arserrc.gov ³Lead scientist, scientist, and research leader, United States Department of Agriculture, Eastern Regional Research Center, Agricultural Research Service, Wyndmoor, PA 19038. Mention of brand or firm names does not constitute an endorsement by the U.S. Department of Agriculture or the University of Illinois above others of a similar nature not mentioned.

A new process was developed to recover corn fiber from the mash before fermentation in dry-grind ethanol production. In this process, corn is soaked in water (no chemicals) for a short period of time and then degermed using conventional degermination mills. In the remaining slurry, corn coarse fiber is floated by increasing the density of the slurry and then separated using density differences. The fiber recovered is called quick fiber to distinguish it from the conventional wet-milled fiber. This study evaluated the percent of quick fiber recovery for a normal yellow dent and high oil corn hybrid. The quick fiber was analyzed for levels of corn fiber oil, levels of ferulate phytosterol esters (FPE) and other valuable phytosterol components in the oil and compared with conventional wet-milled corn coarse and fine fiber samples. Fiber samples were also analyzed and compared for yields of potentially valuable corn fiber gum (CFG, hemicellulose B). Comparisons were made between the quick fiber samples obtained with and without chemicals in the soakwater. An average quick fiber yield of 6–7% was recovered from the two hybrids and represented 46–60% of the total fiber (fine and coarse) that could be recovered by wet-milling these hybrids. Adding steep chemicals (SO₂ and lactic acid) to the soakwater increased the quick fiber yields, percent of FPE recoveries, and total percent of phytosterol components to levels either comparable to (for the dent corn hybrid) or higher than (for the high oil corn hybrid) those recovered from the total conventional wet-milled fiber samples. CFG yields in the quick fiber samples were comparable to those from the wet-milled fiber samples. CFG yields in the quick fiber samples were not significantly affected by the addition of chemicals (SO₂ and lactic acid) to the soakwater.