The Community Nutrition Institute, a public interest group that specializes in food and nutrition issues, has asked the Department of Agriculture for a total ban on the use of sodium nitrite in processed meals.

The president of the American Meat institute, Richard Lyng, has called the proposed ban, "ridiculous. There is absolutely no evidence that nitrite as used in cured meats is harmful," Lyng said.

CNI's petition, filed last week, follows USDA's much more limited proposal to ban the use of nitrites under certain circumstances.

Earlier this fall the agency proposed a ban on nitrites that combine with other substances during processing or preparation to form the cancer-causing nitrosamines. Since the formation of nitrosamines before ingestion occurs mainly in the process of frying bacon, USDA's proposal would apply almost exclusively to that product. USDA has granted a 60-day extension on the deadline for the submission of data concerning the levels of nitrosamines in bacon. Nitrites are used to color, flavor and preserve processed meats.

According to the CNI petition, "the different chemical forms of nitrosamines . . . have been demonstrated to cause cancer in different animal species." Because of this, the public interest organization, which was joined by a coalition of consumer groups in its action, says USDA should "publish a proposed regulation which would declare nitrite . . . a prisonous substance which leads to the formation of compounds which cause cancer and are a health hazard. Products containing nitrites would be considered adulterated."

In its petition, CNI says the "only valid use of . . . nitrites is to inhibit formation for toxin by Clostriduim botulinum spores in some meats.

"However, botulism is not a problem for most meat products. In those instances where botulism can be problematic, the use of nitrite is not mandatory inasmuch as microbiologically safe, economically fearible, and commercially viable alternative methods of processing, packaging and marketing have been developed and are being used at the present time."

The petition maintains that sterile canned products such as corned beef and beef stew do not contain the bacterial spores that cause botulism because of the heating process. Shelf stable meats, including ham salad, deviled ham and Spam are safe, it contends, because of their high salt content and/or lack of moisture. Most fermented sausages, both dry and semi-dry, are safe, it adds, because botulism toxins cannot form in the presence of air.

"Thus," says the petition, "the use of nitrate and nitrite in shelf-stable, sterile-canned products and in fermented sausages and other dry-cured products . . . is primarily for cosmetic purposes only."

Alternatives are suggested: freezing and refrigeration; precooking and a technique called "radappertization," which is the application of small doses of ionizing radiation that destroy botulinum spores.

According to Richard Lyng of the Meat Institute, the large meat processors have not tried these other techniques to insure the safety of processed meats for two reasons: They do not believe people will but them if they lack the characteristic of color and flavor that nitrites impart, and Lyng said, referring to potential hazards from botulism, "I think they are afraid that something might happen."