Food prices to post biggest rise since 1990: USDA WASHINGTON (Reuters) - U.S. consumers should brace for the biggest increase in food prices in nearly 20 years in 2008 and even more pain next year due to surging meat and produce prices, the Agriculture Department said on Wednesday. Food prices are forecast to rise by 5 percent to 6 percent this year, making it the largest annual increase since 1990. Just last month, USDA forecast food prices would climb between 4.5 and 5.5 percent in 2008. "It's a little bit of a surprise how strong some of the numbers were in July," USDA economist Ephraim Leibtag, who prepared the forecast, said in an interview. "We've been waiting for some moderation, but especially with some of the meat prices and how much has come through relatively recently (at the retail level) leads me