Submitted to: Applied Biochemistry and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/21/2007
Publication Date: 1/9/2008
Citation: Sharma, V., Moreau, R.A., Singh, V. 2008. Increasing the value of hominy feed as a coproduct by fermentation. Applied Biochemistry and Biotechnology. 149:145-153. Interpretive Summary: Hominy Feed is a low value animal feed product obtained from the corn dry milling process during the manufacture of food-grade degermed corn grits, meal and flour. The present study investigated the hypothesis that the value of hominy feed could be increased by using conventional yeast to ferment the starch (~56%) in hominy feed, thus creating a new source of fuel ethanol and increasing the levels of protein and fat in the remaining "fermented hominy feed." The experiments confirmed that essentially all of the starch in hominy feed was efficiently fermented to ethanol and the levels of protein and fat increased approximately two-fold in the remaining "fermented hominy feed." Conservative cost estimates indicate that the fermentation of each metric ton of hominy feed (at a current value of about $84) would create about 300 liters of ethanol and 0.75 metric tons of fermented hominy feed, valued at about $180 and 90$, respectively. By fermenting hominy feed to ethanol, ethanol plants could increase ethanol yields and coproduct value, bringing more revenue to the facility, and lowering the net cost of ethanol. Plant owners and ethanol users could both benefit from this process.
Technical Abstract: Hominy feed is a low value ($83.7/metric ton) coproduct of the corn dry milling process that accounts for nearly 35% of the starting corn quantity. The average composition of hominy feed on a dry basis is 56.9% starch, 25.2% neutral detergent fiber, 11.1% protein, and 5.3% fat. Starch in hominy feed can be fermented to ethanol thus increasing its percentages of protein and fat. The increase in protein and fat percentages may increase the market competitiveness and price of hominy feed. Hydrolysis and fermentation was performed on nine hominy feed samples collected from three corn dry milling plants in the US. The original hominy feed samples and post fermentation solids were analyzed for starch, protein, fat and fiber content. Compared to the original hominy feed, the percentage increase in protein, fat and fiber in post fermentation solids of nine samples ranged from 10.4 to 21.3, 6.78 to 10.6 and 12.6 to 28.7% (dry basis), respectively. Ethanol yields varied from 271.7 to 380.2 L/metric ton for the nine hominy feed samples. These results indicate that the value of hominy feed as an animal feedstock can potentially be increased with fermentation and will produce more profit per metric ton than currently being derived by its sale as a low protein feed ingredient.