IN 1977, with much fanfare, Beech-Nut Nutrition Corp. removed the salt and sugar from most of its prepared baby food. The consumer response was so overwhelmingly positive that Gerber and Heinz, the other two baby food manfacturers, quickly followed suit. Today, parents can purchase a variety of baby foods containing no additives other than water.

Even so, many parents have shunned commercially prepared baby food in favor of another brand: their own. Baby food manufacturers say they can't tell whether this trend, combined with later introduction of baby foods, has had any impact on industry growth. There were 1.4 million live births in this country in 1977, and since then the numbers have risen steadily to approximately 1.7 million last year. However despite the increase, total industry sales volume has declined slightly, from 86.6 million cases of baby food jars sold in 1977 to 85 million in 1982, according to figures provided by Beech-Nut.

Aside from the obvious convenience factor, do commercially prepared baby foods have any advantage over those made at home? Dr. George Purvis, vice president for nutrition sciences at Gerber Products Co., says no: not if the homemade foods are carefully prepared. But he emphasizes "carefully prepared." If the cooking water is drained off or if the food is overcooked, said Purvis, the homemade food will have substantially lower nutritional content than the commercial foods.

A 1975 Consumers Union survey compared the nutritional value of home versus commercially prepared baby food; the home variety consistently came out ahead. But Purvis said the study compared "sheep and goats" because the homemade foods were more calorie-dense and therefore had more nutrients. Dr. Thomas Anderson, of the University of Iowa's department of pediatrics, said it's important for parents, when feeding their children homemade foods, not to base the volume of the serving on the standard serving contained in a commercial baby food jar, since this can lead to excess calories.

Baby food manufacturers always have prided themselves on the high quality of their products. "Their quality control is in fact quite good," said Dr. Samuel J. Fomon, professor of pediatrics at the University of Iowa, Iowa City.

Gerber's Purvis said each production lot is monitored for residues of environmental contaminants and pesticides, and agronomic practices are carefully controlled to avoid insecticide and fertilizer misuse. But Purvis is reluctant to claim that Gerber's baby foods are freer of toxins than homemade foods. That, he said, would be implying that the food supply is contaminated--an assumption he discouraged.

One of the main advantages of preparing baby food at home is cost. Besides being less diluted with water than commercially prepared baby food, homemade foods can be divided in portions suitable to the infant's appetite at each stage of development. But to produce high-quality baby foods, the following precautions must be taken:

* Before preparation, wash your hands, cooking utensils, cutting board and counter in hot soapy water and rinse well. Keep raw meat and poultry away from the preparation area.

* Use the freshest foods possible. Canned fruits and vegetables should not be used because of the added salt and/or sugar. The lead content from soldered seams in canned foods also can be a problem for an infant. Also avoid frozen foods with added salt.

* Peel fruits and vegetables. While this means a loss of some nutrients, there also will be less dirt, fewer microorganisms and pesticide residues and less tough fiber for the baby to digest. Remove fat, gristle and skin from meats.

* Steam vegetables and fruits until just tender enough that the baby will accept them, then mash or pure'e lightly in a blender. If the produce was cooked in a small amount of water, use the cooking liquid for pure'eing. Meats can be prepared any way but frying.

* Don't add sugar, salt, butter, fat or spices to an infant's food. If the baby is to eat table food, prepare it before seasoning.

* The prepared food can be safely refrigerated for up to three days or frozen for a month in ice cube trays.

There's been some concern in the last few years about feeding vegetables high in nitrates, especially spinach and beets, to infants. The nitrates, if converted to nitrites by bacteria while the vegetable is being stored, can be absorbed into the blood stream of the young infant and reduce the amount of oxygen circulating in the blood. In rare instances, methemoglobinemia, a condition marked by blue skin and difficulty in breathing, can result. The condition is more common in Europe where carrot juice is sometimes given to infants with diarrhea. Carrots themselves don't have a high nitrate content, but the nitrates can be very high when the carrots are concentrated in juice form.

Registered dietitians Jo-Ann Heslin, Annette B. Natow and Barbara C. Raven, in their book "No-Nonsense Nutrition For Your Baby's First Year" (see sidebar, page xxx), recommend that beets, spinach and carrot juice be withheld from infants until they are at least 6 to 8 months old, and that when they are served, they be limited to no more than one serving every other day. Frozen vegetables are preferred if beets and spinach pure'es are prepared at home, since the freezing inhibits the bacterial action that can convert the nitrate to nitrite.

Parents who use commercially prepared baby food should read labels carefully. Modified food starch still is used in some of the foods, to achieve a certain texture and to prevent separation of the solids and liquids, but consumer groups have complained that the starches have not been adequately tested specifically to determine safety for infants. Some manufacturers now are relying more on unmodified starches, such as cornstarch.

Likewise, the manufacturers still add sugar to some of the tart fruits such as plums and apricots, and to the "dessert" items--items most nutritionists believe unnecessary in an infant's diet.

The Society for Nutrition Education, a professional group of nutritionists, in a parents' guide called "First Foods," advises purchasing plain, rather than mixed vegetables, meats and cereals "for the best value nutritionally and economically."

In addition, SNE tells parents to wash food jars and lids thoroughly before opening and to avoid feeding directly from the jar if the remainder of the food is to be used for another meal. This is because the digestive enzymes from the baby's saliva can contaminate the remainder of the food.

Purvis said Gerber still has concerns about its decision to remove all the salt from baby foods. "As a margin of safety, we would like to add carefully controlled amounts," he said. A 1979 survey conducted by Purvis of 154 infants found 16 percent younger than 8 months of age received less sodium than the safe and adequate daily intake set by the National Research Council of the National Academy of Sciences.

Purvis also is concerned that parents are adding salt to the unsalted baby foods after tasting them. But the company has neither professional nor consumer support to add salt to foods, Purvis said.

As for the order in which solid foods are introduced, it probably is not that important if parents wait until their children are 5 or 6 months old before starting solids. Cereal usually is the first food introduced, followed by fruits and vegetables and then meats. Some nutritionists recommend introducing vegetables before fruits, so infants won't reject the vegetables because they lack sweetness.

Pediatricians recommend introducing each new food separately, and then waiting at least five days before another new food is added to the baby's diet, to make sure there is no allergic reaction. Here are some recipes to try. FRUIT AND VEGETABLE PUREES (6 to 7 months of age)

Mash with fork or food mill one of the following: Very ripe banana; cooked sweet potato; steamed or baked winter squash, carrot, apple, pear, peach.

Add apple juice, white grape juice, pineapple juice or other liquid such as milk or chicken broth until desired consistency. STEWED DRIED FRUITS (6 to 15 months of age)

Place dried apricots, peaches, prunes or raisins in a saucepan that is large enough for fruit to swell. Cover fruit with water and quickly bring to simmer. Cover and cook until soft, approximately 10 minutes for raisins and 45 minutes for larger fruits. Pure'e cooked fruit and cooking liquid in food mill or blender. Pour into ice cube tray and freeze. These fruit pure'es can be eaten alone or added for variety and sweetness to cereal, mashed cottage cheese, bland vegetables, plain yogurt, meat or tart fruits. POULTRY OR VEAL STEW (9 to 11 months) (16 1/2-cup servings) 2-pound turkey leg, skinned; chicken breast quarters, skinned; or veal shoulder 1 quart water 3 carrots, sliced 2 stalks celery, sliced 1 teaspoon dried parsley 1/2 cup rice, uncooked 2 cups frozen early peas or 1 1/2 cups frozen peas and 1/2 cup shredded lettuce

In covered pan, simmer meat in water for 40 minutes or until fork-tender. Add carrots, celery, parsley and rice; simmer 10 minutes. Add peas and cook for 20 minutes. Remove meat from pan and discard bones and tendons. Grind meat, using enough cooking liquid to ease operation of blender or food mill. Pure'e vegetables and rice with more cooking liquid. Combine meat and vegetable pure'es. Pour into ice cube trays and freeze.

Note: Pure'ed meats tend to have a grainy texture--a problem even commercial manufacturers have to deal with--but by the time babies are 9 or 10 months old, they usually can handle soft meats such as boiled poultry or flaked fish that is mashed with a fork. POACHED FISH (9 to 11 months) (2 servings) 1/4 pound fresh fish fillet (frozen fish often has been packed in salted water) 1/2 cup water or vegetable stock 1/2 teaspoon lemon juice 1/2 teaspoon dried parsley or 1/4 bay leaf

Simmer fish, stock, lemon juice and parsley in covered saucepan, or until fish flakes easily. Mash with fork and adjust consistency with poaching liquid. CREAM OF BROCCOLI (9 to 15 months) (2 servings) 1/4 cup fresh broccoli florets (or cauliflower) 2 tablespoons cooked rice (or 3 tablespoons mashed potato) 3/4 cup hot formula or milk Steam vegetable. Combine with rice and milk and blend until just smooth. Pour 2/3 cup of pure'e into ice cube tray and freeze immediately. Serve remainder. PEA AND EGG YOLK CUSTARD (9 to 15 months) (2 servings) 1/4 cup pureed peas 1 egg yolk 1/4 cup milk

Blend together ingredients, pour in custard cups and place in shallow pan of water. Bake at 350 degrees for 30 minutes. Next Wednesday: Foods for older children.