This weekend the Portuguese of New Bedford, Mass., are celebrating the annual Feast of the Blessed Sacrament. The festival dates back to 1914 when four Portuguese immigrants from Maderia promised a celebration if their small boat braved the stormy voyage across the Atlantic to New Bedford. THelena Costa hopes to return to New Bedford for the festivities. Until last year, when her husband, Tony, became acting chief of the Voice of America's Portuguese to Europe program, the Costas lived in New Bedford. There Helena wrote a "Portuguese Cooking" column in the Portuguese Times.

A third generation American, Helena still cooks and practices the food customs of her ancestors from the Azores and Maderia. Some time ago she began interviewing Portuguese women in this country and in Portugal, collecting more than 150 recipes for a book she is doing. Since moving here, Helena has been teaching Portuguese cooking to neighbors in her Van Ness apartment house.

Portuguese saliors, explorers and fishermen have been living in New Bedford for decades, with many families dating their arrival back to the heyday of whale and cod fishing in the middle of the 19th century. Since both the Portuguese Azores and Cape Verde Islands were provisional stops for whaling ships and clippers, natives of these islands migrated to New Bedford. Still others are from Madeira and the mainland.

Iberian food, Helena explained, always has been considered del pueblo, food of the people. Despite regional differences of spices and vegetables, Portuguese dishes always include a strong blend of fresh ingredients. Besides a large array of fish they use olive oil, garlic, fresh tomatoes, wine, onions, parsley, potatoes, eggs and almonds.

Often fish stews are cooked in heavy earthenware pots which preserve the melding of tastes. caldereida, a Portuguese fish stew, is a provincial dish eaten at lunch on Sunday. The variety of fish may vary according to the season, but the basic ingredients remain the same.

The choice of fish is important. At the market Helena insisted on picking each hard-shelled clam from the cooler herself. Heads and tails of fish are essential to her fish stews. Most fish markets will give them to you, but call ahead to reserve them.

At Easter Helena makes massa sovada, the famous Portuguese sweet bread. The name literally means "punched or beaten dough." When the dough is ready to rise she says in Portuguese, "May you rise with the grace of God." Then she makes the sign of the cross and covers the dough.

Helena learned this custom from her grandmother, who believed that in this way only the bread will rise. To Helena there is still a certain mystery in the rising process.

An old Azorean tradition is to use the loaf as a healing device. If, for example, a person has a disease affecting an arm or a leg, the loaf will be formed into the shape of the afflicted limb.

Although traditionally served at Easter, the sweet bread can be eaten at any special occasion throughout the year -- at weddings, christenings or friendly gatherings. Serve it with the following Portuguese fish dishes.

CALDEIRADA

(Portuguese Fish Stew)

(6 to 8 servings) 2 large onions, chopped coarsely 4 cloves garlic, crushed 1/2 cup olive oil 4 cups peeled and seeded fresh tomatoes, diced (or canned, stewed tomatoes) 1 green pepper, chopped coarsely 2 cups water or fish stock made from 1 pound fish heads* 2 tablespoons tomato paste 3 tablespoons chopped parsely 1 bay leaf 1/2 teaspoon thyme 1/2 teaspoon saffron 1/4 teaspoon cumin 1 teaspoon salt 1/8 teaspoon pepper 4 potatoes, peeled and quartered 3 pounds assorted fish and shellfish, cut in 2-inch pieces (haddock, cod, halibut, rockfish, shrimp, scallops, clams or mussels) 1 tablespoon hot red pepper

*Made by simmering fish head (covered) in water with 1 bay leaf and 1 teaspoon salt for 1/2 hour then straining.

Saute the onions and garlic in oil in a heavy pot or Dutch oven until golden. Add the tomatoes, green pepper, water or fish stock and tomato paste. Bring to a boil. Add the parsley, herbs and salt and pepper. Simmer covered about 20 minutes. Add the potatoes and simmer 20 minutes longer.

In the meantime scrub the clams and then soak in cold water with 1 tablespoon hot red pepper.

Add the thick fish and simmer covered 10 minutes. Next add delicate fish such as the sole and shellfish and cook 10 minutes until the clam shells are open. Remove the bay leaf and serve with hot crusty bread.

MAIONESA DE LANGOSTINOS (Langostino Salad Platter) (6 servings) 8 medium boiling potatoes, peeled 1 pound green beans, French style 1 pound cooked langostinos Shredded lettuce 2 cups homemade mayonnaise (see below) Black olives for garnish 2 hard-cooked eggs

Cook, cool and cube the potatoes. Cook the green beans until tender.

In a large salad bowl combine the potatoes, green beans and langostinos. Mound on a large serving platter on a bed of shredded lettuce. Cover with mayonnaise and garnish with black olives and sliced eggs.

HOMEMADE MAYONNAISE (Makes 1 1/2 cups) 1 egg 1/4 teaspoon dry mustard 1 teaspoon salt 2 tablespoons lemon juice 1 1/2 cups olive oil

In a blender or food processor beat the eggs until thick. Add the mustard, salt and lemon juice, blending well. Very gradually add the olive oil, mixing constantly.

PORTUGUESE SWEET BREAD (Makes 4 loaves) 2 cups milk 2 cups sugar 1 teaspoon salt 1/4 cup (1 1/2 sticks) unsalted butter 2 packages dry yeast 1/2 cup very warm water 6 eggs 10 cups all-purpose flour

In a heavy saucepan, combine the milk, sugar, salt and butter. Heat until warm, stirring occasionally to melt the butter.

Dissolve the yeast in 1/2 cup very warm water in a large mixing bowl. Add lukewarm milk mixture, 5 of the eggs and about 3 cups of the flour. Beat until smooth, scraping the sides of the bowl constantly.

By hand, stir in the remaining flour and knead thoroughly about 10 minutes. Keep folding dough when it blisters, looks satiny and starts to leave the knuckles. Let dough rest uncovered about 30 minutes and knead again 10 minutes. Repeat this process once again. Cover bowl with plastic wrap and clean towel and let rise until double in bulk, about 5 hours.

Punch dough down; knead a few times and let rest 5 minutes.Divide dough into 4 equal portions. Place in well-greased loaf pans. Cover and let rise until top of dough is slightly above sides of pans.

Beat the 1 remaining egg and brush the tops of bread with it. Bake bread in a 325-degree oven for about 15 minutes. Reduce heat to 300 and continue baking until golden brown, about 30 to 35 minutes longer. Cool slightly in pans on wire racks; remove from pans. Cool completely and keep fresh in plastic bags. CAPTION: Picture, A third generation American, Helena Costa still cooks and practices the food customers of her Portuguese ancestors; by John McDonnell -- The Washingtoon Post.