Food prices have not been forced up by ethanol, say University of Nebraska economists, because grain prices are a function of the world market, and farmgate food prices are only 20% of the food dollar. See www.agecon.unl.edu/Cornhuskereconomics/2008/2-13-08.pdf.
Since the value of corn used in domestic food production is only 16% of all farm production, then 16% of the 20% received by farmers is only 3.2%, hardly enough to inflate food prices. Their rationale is at: www.agecon.unl.edu/Cornhuskereconomics/2008/2-13-08.pdf