New federal regulations will require sufficient heating of precooked roast beef to kill potential food poisoning bacteria, the Department of Agriculture announced last week.

Such meat, sold to the public in delicatessens and delicatessen counters of supermarkets, fast food outlets and restaurants, has been responsible for a number of outbreaks of food poisoning this summer.

Assistant Agriculture Secretary Carol Foreman said all meat processors "who prepare precooked roast beef" must heat it to an internal temperature of 145 degrees to destroy any salmonella bacteria. Before her annoucement there were no regulations governing the temperature for cooking roast beef.

USDA officials said it could take up to two months to replace all precooked rare roast beef now on the market. Foreman advised consumers to reheat any suspect rare roast beef to the 145-degree mark to prevent possible illness.

Community Nutrition institute, a public interest group that monitors federal food and nutrition programs, is not satisfied with USDA's response to the salmonella outbbreak. It petitioned the agency to "alert the public to the potential hazard of food poisoning from undercooking meat that has been shipped in vacuum-packed plastic containers and/or which has been mechanically tenderized."

CNI has also asked USDA to "develop practices and establish requirements which will minimize public exposure to microbial contamination of meat which is shipped in plastic packages under vacuum, and, until these practices and requirements are implemented, prohibit or restrict the use of vacuum packaging of meat . . ."

In its petition CNI said the vacuum packaging is often responsible for the growth of the bacteria. "Under the righ conditions - temperature and enough time" the fluids which are drawn out of the meat into the plastic bag "become a growth culture for bacteria which is normally present on the surface of the meat."