BANGOR (AP) – Food retailers in Maine are having a tough time keeping their shelves stocked with enough organic milk to keep up with demand.

Maine leads the country in the percentage of its dairy farms that are organic. But even with multiple suppliers, some retailers say they can’t get enough.

“We can’t even get a true reading of the demand because it flies off the shelves,” said Judy Chong of Shaw’s Supermarket chain. “There is just not enough supply.”

Consumers in 2005 are spending twice as much on organic food as they did in the 1990s, according to Mintel, a market research company. Mintel found that overall sales of organic dairy products increased 78 percent between 2001 and 2004, and that 44 percent of all organic foods are now being purchased at mainstream retail outlets.

In New England, sales of organic milk grew 60 percent last year, compared to 20 percent nationwide, helped by mainstream supermarkets that now carry full lines of organic dairy products.

At Shaw’s, Chong said the stores are seeing sales rise for other organic products. “The demand for organic is rippling right on down the line,” she said.

At Hannaford, spokeswoman Caren Epstein said the company is reconfiguring its dairy cases to make room for more organic dairy products.

Caragh McLaughlin of The Organic Cow of Vermont, a 15-year-old organic milk supplier, said people are turning to organic dairy products because of food safety and personal health concerns.

Maine has the largest proportion of dairy farms in the country producing organic milk – 63 farms, or 15 percent of all dairy farms in the state, up from just 11 farms in 1997. The Organic Cow buys milk from organic dairy farms across the Northeast.

“There is not enough organic milk supply in the country, in New England and Maine especially,” McLaughlin said.