By Lisa Shumaker

CHICAGO (Reuters) - Worries that the U.S. government will repeal or soften mandates on blending ethanol with gasoline sent shares of Archer Daniels Midland Co (ADM.N: Quote, Profile, Research) down 4.7 percent on Tuesday, even as ADM posted a 42 percent jump in quarterly profit.

The chief executive of ADM, a leading alternative fuel producer, defended the use of corn to make ethanol as food prices rise around the world, leading to riots and many countries limiting exports. There are growing calls for the United States to cut a tax credit of 51 cents a gallon for ethanol blenders and eliminate a tariff on ethanol imports. [nN25178749]

"I actually find it sad, and even a little ironic, that this attack on biofuels is directed to the one alternative we have today," Chairman and CEO Patricia Woertz said on a conference call with analysts.

"Biofuels are a real solution to a real problem. To retreat from biofuels is wrong. It's foolish. It's dangerous. It's an empty gesture. It won't fill anyone's stomach. It won't fill anyone's gas tank," she added.

About 25 percent of U.S. corn is turned into ethanol, according to U.S. Agriculture Department estimates, and corn futures have risen 70 percent in the past year and hit record highs on increased demand to use the grain both as food and fuel. [nN28175022]

Earnings jumped to $517 million, or 80 cents per share, for the third quarter ended March 31, from $362.9 million, or 56 cents per share, a year earlier. Analysts, on average, expected 70 cents, according to Reuters Estimates.

The futures trading desk in its agricultural services division helped boost earnings, even as record corn prices hurt profits from selling sweeteners, starches and ethanol.

"The trading desk benefited from a lot of the volatility in the market, and the risk management was in their favor," said Morningstar analyst Ann Gilpin. "The fear is that ADM is a large ethanol producer, and they're making less money on their ethanol sector."