BILLINGS, Mont. — An orthodox rabbi from Bozeman has opened Montana's first kosher certification agency as part of his drive to bolster Judaism in the Big Sky State, where fewer Jews live than almost anywhere else in the country.

Rabbi Chaim Bruk said his first client, a Gallatin County grain plant, could be certified as kosher sometime next month. Among observant Jews, kosher law defines what foods are fit for consumption and how they must be prepared.

Bruk moved to Montana from New York in 2007 to conduct outreach for the orthodox Chabad Lubavitch movement of Judaism.

"If I was in New York as a rabbi I wouldn't have to deal with kosher because there's enough agencies in New York that do that," he said. "But there's no reason why somebody running a business in Victor, Mont., or somebody running a plant in Helena should not have the opportunity to expand to the kosher market."

There are about 5 million Jews in the U.S. Estimates for the number in Montana vary widely.

The American Jewish Year Book put the figure at 850 several years ago. Bruk estimates as many as 5,000 out of Montana's 989,000 residents could be Jewish. There are nine congregations in Montana, generally in the state's larger towns and cities.

Most of those are reform congregations. While their members may not share Bruk's orthodox views, the rabbi said he hopes his work promoting kosher will promote "good old authentic Judaism" to a broader audience than just his immediate followers.

Rabbi Barbara Block of Congregation Beth Aaron, a reform congregation in Billings, said staying kosher is gaining renewed favor among some reform Jews, who see it not just in a traditional context but also an ethical one. Block said many seek out a specific kosher label that emerged in recent years to signify environmentally friendly food production, known as eco-kashrut.

"It's taking a broader view of how our food is produced — were the animals treated humanely, were the workers treated humanely," Block said. "We all take the tradition very seriously and have different views about how it is best expressed."

Under an arrangement with out-of-state certification agencies, Bruk says he has helped certify several businesses as kosher including bakeries, grain producers and a vegan cheese maker.

Montana Gluten Free Processors sought certification last year after landing a contract deal with an Israeli company that wanted gluten-free oat flour for Passover, said Rob Miller the Belgrade company's grain miller. About half of the company's total 2010 production of 4,000 bushels will go to Israel and the rest to Montana buyers, Miller said.

To be certified, companies must be inspected by a rabbi or kosher supervision agency to ensure processed foods are free of non-kosher ingredients.

Before Bruk certified Miller's oat crop on behalf of a Denver rabbi, Bruk inspected the combine and rode along during the cutting of the oats. He later labeled the bags the grain was put in and would show up ever morning to start the grain processing machinery, Miller said.

Other rules of kosher include separating meat and dairy products, a ban on pork and some fish and prescribed procedures for killing animals including cutting their throats with a special knife.

Sue Fishkoff, the California-based author of the recently released "Kosher Nation," said companies with kosher food offerings tap into a wider market than might be expected.

Non-Jews with diet restrictions are often drawn to certified foods, including vegetarians who seek out the special kosher label that means there is no meat in a product, and lactose-intolerant eaters who want items without dairy ingredients.

"There are about 12 million regular kosher consumers and only one million are Jews who keep kosher," Fishkoff said. "People who are regular kosher consumers are buying kosher meat, for example, because they believe it's healthier or safer or better."

While kosher law has been around for centuries, Fishkoff said certification is a 20th century response to the industrialization of the American food supply.

The first certification on a national level was awarded in 1923 for Heinz Vegetarian Beans. It has since expanded dramatically, with an estimated 40 percent of food sales now kosher.

The vast majority of items are deemed kosher by one of four major certification agencies, Star-K, Orthodox Union (OU), OK Kosher and Kof-K.

But Fishkoff said there are up to 1,000 individual agencies, most of them lone rabbis who limit their work to neighborhood businesses that serve their own congregations.

Bruk has broader ambitions — certifying food producers as kosher across as much of Montana's 147,000 square miles as he can cover.

"Right now funding is tough but I really believe in what we're doing. I believe in the next few months. We'll see profit from work."