Steve Barnes does not consider myself purist when it comes to food. He is not, he says, like some of the others at the cooperatively run, alternative food store where he works.

While he may not be as fierce in his beliefs about food. Barnes still was the one worker at the University of Maryland's student controlled food coop who, three weeks ago, urged his coop colleagues to stop selling chocolate milk.

When Barnes proposed the idea at one of the store's weekly meetings it touched off a minor battle within the group. The chocolate milk in question contained sugar, modified food starch and some preservatives - three basic no-nos among any group of self-respecting health food advocates.

The fight was between the pro-organic forces, for whom almost all chemical additives are nothing less than sinful, and the less dogmatic, give-the-customers-what-they-want-forces, who dislike preservatives but claim the milk not only is a strong selling item but tastes good as well.

While the chocolate milk episode is not by itself particularly significant, it is indicative of the rigorously moral and political dimensions that the university coop workers bring to such disputes.

For the past three years, the students who run the worker-controlled, "anti-profit" campus food cooperative have made up the core group of leftist activitists at the university. They have inherited the somewhat ambiguous legacy left by the antiwar radicals of the 1960s and molded it into their own brand of grocery store socialism.

Their motto, prominently displayed on a bold red-lettered sign hanging in the store's front door is "Smash Capitalism."

The store's existence has not, as yet, had a significant impact on the nation's economy, but it has affected the other university operated food outlets on campus. School administrators, who fought the store's opening, now readily admit that the coop has won over a sizable number of customers who might otherwise patronize the university's cafeterias.

The main attraction apparently is the shop's relatively low prices and individually tailored sandwiches that can include freshly shredded carrots, onions, mushrooms, sprouts, green peppers and a variety of cheeses.

"I think it's a mixed blessing," said chancellor Robert I. Gluckstern. "They do provide a service to the people on campus. The emphasis on health foods is a good idea. However, it does compete with the (university) food service. But I think that's good. I've had several reports that food service has improved as a direct result of competition with the coop," he added.

When students first came up with the idea about four years ago, school administrators did not have such a benign attitude. The university's Board of Regents actively opposed the idea, voicing fears that a coop operating from state-owned and subsidized buildings would create unfair competition for local merchants.

As a result, it took months of tedious negotiations - punctuated by a few well-trained demonstration - before school administration allowed the coop to move into a room in the student union.

Not that the coop's organizers minded. That are proud that they got their start battling school administrators. They consciously cultivately a radical image.

In an age of the blow-dry hair style, most coop members wear their hair long and unkempt. At work, they usually don red bandanas. Almost every inch of wall space in the small shop is covered with posters, so that a coop patron waiting for a sandwich is bombarded with causes: "Eat Whole Grains." "Save The Whales." "Stop the Land Grab, Support Indian Treaties." "Love Animals, Don't Eat Them." "Condemn The South African Regime." And so on.

Overlooking this whole operation is a life-size color poster of Lenin. For the coop organizers, food and politics are inextricably intertwined.

"The food coop's function is to provide an economic alternative to the other (university-run) food services, to support student causes and to make students aware of global issues," says Joe Yuhas, a worker at the store since it opened. "More than anything else, the coop as a political force has been a place, a physical identify place" for campus activits to meet and organize," Yuhas said.

Although the meetings and rallies are not usually overcrowded, coop leaders have in recent years successfully organized many movements around a few key issues, fighting anything from tuition increases to the university's investments in firms doing business in South Africa. Most recently, coop members have staged demonstrations on behalf of Bertell Ollman, a Marxist whose proposed appointment at chairman of the government and politics department at the College Park campus was recently rejected by incoming university president John Stoll.

To demonstrate their support for Ollman, a band of coop workers who support the use of confrontation politics, showed up with picket signs at a recent regents meetings and engaged in a shouting match with the board's chairman, B. Herbert Brown.

While the mixture of food and political achivism has apparently been a successful combination for the university food coop, some students who work there say that politics permeates business decisions to such an extent not the questions of what food to carry becomes the subjects of arcane philosophical disputes.

For instance, ever since the store opened, coop members have been engaged in a debate over whether to serve meat. Ham, because it contains preservatives, was eliminated from the store menu some time ago and now turkey is the only meat sold. Still the dispute rages.

Goldstein, who favors the elimination of meat from the store, says there would not be a world hunger problem if people stopped eatings meat. To fatten livestock for slaughter, he contends, requires hugh amounts of grain - grain that could be put to more efficient use feeding people directly.

Goldstein's fellow coop members agreed with his philosophy as it applied to the raising of pigs and the selling of ham. They balked when a prohibition of turkey was recommended. Turkeys, many coop members decided, are not grain guzlers - at least not enough to warrant the exclusion of turkey meat from the store.

In any case, Yuhas believes, that the store has a responsibility to its meat-eating customers. "We have to realize that people in the community want turkey and we exist to serve them," he said.

Yuhas and his adherents also came out on top in the great chocolate milk donnybrook. The coop voted to stop selling the product, but, one week later, after workers were swamped with patrons' complaints, chocolate milk - sugar and preservatives included - was back on the store shelves.

"It's bad that we spend so much time, hours at a meeting, deciding whether to drop chocolate milk," Yuhas said. "Those things are important but it's become exhaustive. We get carried away."

"It's not the discussion that makes the time wasted, but people state their points five times just to hear themselves. That's the thing I hate most," says Goldstein.

Gluckstern apparently would prefer coop members to spend more time selling food and less time confronting the regents.

"I suppose I wished they would be a little less involved (politically)," he said. "Their tendency to get into confrontation politics is a bit unfortunate, but I think it's wrong for me to say this kind of behavior is appropriate and this kind isn't. I consider it (the coop) an asset to the campus despite the fact that it occasionally causes problems."