Every major chain supermarket in the greater Washington area will be closed this Sunday so store employes can vote on a new union contract to replace one that expires at midnight Saturday.

Food chain officials yesterday described the decision to shut their stores as routine and said it does not mean there is a danger of a strike by members of Local 400 of the United Food & Commerical Workers Union.

"We're hopeful of a peaceful settlement," said Barry Scheer, spokesman for Giant Food, who said Giant's stores closed for a contract vote three years ago.

"It doesn't mean a thing" about the status of contract talks, added Ernie Moore, Safeway's spokesman.

Officials of Local 400, the biggest labor organization in the Washington area, could not be reached for comment.

The union represents checkers, stock clerks, butchers and most other supermarket employes and negotiates jointly with a committee representing Giant, Safeway and the other chain supermarkets in the area.

Supermarket officials have been saying for several weeks that they expected to settle with Local 400 without a strike.

Earlier this summer the chains were struck by bakery employes, which cut off the most supplies of bread and pastries for several days.

Bread prices jumped by a few cents a loaf after that strike was settled, and other food prices also could be pushed up if Local 400 wins big raises, industry sources admit.

Negotiations are taking place as supermarket competition in the Washington area is at an usually high level. The recession and rising food prices have made consumers more price-conscious, and the major chains are struggling against competition from new kinds of low-price food stores.

Giant and Safeway are preparing to open their own cut-rate operations with smaller selections and fewer employes in an attempt to keep from losing business to the new competitors such as the Plus stores owned by A & P and Grand Union's Basics discount operations.

Safeway plans to open a pair of Food Box stores in the District of Columbia next month that will carry only about 1,000 items, a fraction of what a fullsize Safeway stocks.

Giant's first experimental unit will open next Wednesday in Clinton. The chain is keeping the name secret and says the store will be "totally unique" in the food industry.

The sign near the building just off Branch Avenue now says "Giant Test Store." Inside, the usual display shelves have been replaced by new fixtures that hold groceries in their shipping cartons. The store will carry about 2,500 items rather than the 10,000 of a conventional supermarket.

Giant officials have said the store will have the same pharmacy, produce, meat, delicatessen and seafood departments as conventional Giant supermarkets and will offer the same customer services, including bagging and check-cashing. a

Safeway's experimental stores will have no such services -- although they will take food stamps -- and will make customers bag their own orders and either bring their own bags or pay 3 cents apiece for them.

Safeway's Food Box stores are the second such experiment for that chain, the biggest in the business. A few months ago Safeway opened what it called a Food Barn store in Baltimore County.

Safeway's Food Box will carry fewer items than the Food Barn -- about 1,000 compared with 2,500. While the Barn carries most national brands, the Boxes will be stocked almost exclusively with Safeway's private-label items.

Originally Safeway planned to stock some fresh meats in the Food Box stores, but that idea was dropped because union contracts require stores to be staffed with butchers if they sell meat.