A couple celebrates a special anniversary with an intimate dinner, soft candlelight and a bottle of fine wine. Would the romance be diminished if they looked at the label and discovered they were also sipping corn syrup? Or carboxymethyl celulose?

Would a beer drinker like to know if he was imbibing a foaming agent called propylene glycol alginate? Or would he prefer to down it in ignorant bliss?

After years of pondering such sticky questions, the Treasury Department last year adopted a controversial regulation requiring labels on alcoholic beverages to list the drink's ingredients or provide an address where consumers could write for such information.

At the time, the department's Bureau of Alcohol, Tobacco and Firearms (BATF) said that the requirement, which would have taken effect in 1983, would let consumers "make more informed choices about alcohol beverages," and would offer "benefits and savings which exceed the cost of ingredient labeling."

But by this May, the department had changed its view. Looking at the regulation in light of President Reagan's executive order on regulatory reform, the department proposed to rescind it because it did not appear to be "truly necessary and cost effective," said Robert Maxwell, deputy assistant director for regulatory enforcement.

Last week, BATF extended the deadline for comments on its proposal to rescind the regulation to Aug. 5. But consumers advocates and alcoholic beverage producers agree that the delay is just postponing the inevitable and the regulation probably will be killed.

"It's a classic case of how industry fights off a sensible regulation that could help consumers a little bit," said Michael Jacobson, director of the Center for Science in the Public Interest, the most vocal consumer group on the issue.

The industry, meanwhile, calls the regulation a case of "government overkill" in a matter that doesn't interest the public.

"It's a matter of honor," said Doug Metz, executive vice president and general counsel for the Wine and Spirits Wholesalers of America, a trade association of wholesalers and distributors of domestic and imported wines. "When you take as much pride in producing wine -- and it is an art form -- [required labeling] is really a slap in the face."

It's also a matter of money, particularly for companies in Reagan's home state. Last February, 16 California congressmen from wine-making areas wrote Treasury Secetary Donald T. Regan urging that the regulation be revoked because the total cost of implementing the proposal "would results in an added cost to consumers for all American and foreign wines over $90 million each year." Last month a similar letter was sent to Deputy Treasury Secretary John Walker, signed by California's two senators and 40 of its congressmen.

And in a speech prepared for the San Joaquin Farm Bureau Federation in Stockton, Calif., last month, Agriculture Secretary John R. Block said that "the cost of this regulation to the consumer ($137 million per year) and the cost of the government to administer it ($200,000 per year) makes this action totally unrealistic."

But Jacobson contends the cost would be negligible, especially since the regulation would not take effect for two years, when the wine companies, at least, would have to modify their labels to show that the grapes are from approved wine-growing districts.

Ingredient labeling for alcoholic beverages has been proposed in various forms for the past seven years, with the Food and Drug Administration insisting at one point that it should be in charge of the regulations, until a federal court ruled in favor of the Treasury Department.

Some beer labels already provide at least a partial list of ingredients, such as "choicest barley" and "hops," but the lists may omit other approved additives, according to a Treasury Department official.

The industry argues that listing ingredients could confuse the consumer. "If you read a list of rice, wheat, grains, you're going to think 'My heavens, I'm having cornflakes for breakfast'," said Metz.

Arthur Silverman, counsel for the wine institute agreed, saying that if wine is made from grapes that are particularly low in sodium, wine-makers may add some sodium to make up the deficiency. A person on a low-sodium diet may read the label and decide not to buy the wine, even though the additive merely brings the wine up to the normal sodium level, he said.

But grain and grapes aren't the only things that go into some alcoholic beverages. Benzaldehyde (an artifical flavoring for beef), sulfur dioxide (a preservative used in some wines), and gum arabic (a thickening agent in distilled spirits) are sometimes used.

The additives have been approved by the Food and Drug Administration, but Jacobson contends that they could be dangerous because they have not been tested with alcohol. He added that, in any case, additives should be listed so that people who suffer allergic reactions to them can avoid the beverages.

FDA officials maintain that the additives have been tested sufficiently. Gerad McCowin, director of the division of food and color additives, said it would be extremely difficult and expensive to test all the additives that way.

The officials also say the likelihood of allergic reaction to additives in alcohol is very small. But Jacobson, in response, cites a 1963 incident in which 16 beer drinkers were poisoned by cobalt sulfate, a beer additive that has been banned since then.

Both industry and consumer groups say they're fighting for a matter of principle.

"People have a right to know what they're drinking," said Jacobson.

But Silverman, of the wine institute, said, "Wine is unique from other foods, and we want it to be treated as such . . . If you're talking about cake mix, that's another story."