General Mills Inc. and other big food firms have been snapping up organic brands in recent years, putting them in an uncomfortable spot with organic consumers in California's food labeling battle.

The food giants have ponied up big bucks to defeat Proposition 37, which would force them to label products made from genetically engineered (GE) ingredients. But many organic consumers support Proposition 37.

Some are miffed that the owners of their favorite organic brands are working to kill it.

Organic consumers "are people who care about their food supply, and they want to know what's in it," said Mark Kastel , co-director of the Cornucopia Institute, a Wisconsin-based organic industry watchdog group. "They are the pinnacle of label readers."

By opposing Proposition 37, General Mills and other organic foodmakers "are eroding their brand equity by betraying the values of their customer."

General Mills declined to make an executive available for an interview. In an e-mail, the company said it has long believed that labeling regulations should be set at a national level, not state by state.

"Because state-based laws would require products to be labeled differently in each state -- increasing the cost for companies and consumers alike -- most companies take a similar view," General Mills said in the e-mail.

Organic food is grown under stringent rules aimed at reducing farming's environmental footprint, including the prohibition of pesticides, herbicides and GE crops. Organic is also a fast-growing business, generating more than $20 billion in annual U.S. retail sales.

Kraft, Kellogg, Coca-Cola, PepsiCo and other big food firms have branched off into organic brands. Many of them are funding the opposition to GE labeling in California.

General Mills' organic efforts are housed in its Small Planet Foods division, which had $249 million in sales in its most recent fiscal year, up 19 percent over a year ago.

Its main organic brands are Larabar, an energy bar line; Muir Glen, known for its tomato products; and Cascadian Farms, where products include cereal, granola bars and frozen vegetables.

The hubbub over Proposition 37 has boiled over onto the Facebook sites of Cascadian Farms, Muir Glen and other organic brands owned by big food companies.

"I just purchased a box of your cereal, and I'm so incredibly angry I could spit nails," a customer named Deb Russell wrote on the Cascadian Farms website recently. "How dare your company donate against Prop 37? That makes you the lowest of the low. Why do you want to kill people?"

Casacadian Farms replied to her that it doesn't use genetically engineered products and never will. "While our parent company believes that labeling should be enacted at a national level, we remain committed to organics."

Mike Hughlett • 612-673-7003