Nati Harnik / AP file

A sample of lean finely textured beef, also known as 'pink slime,' is displayed at the Beef Products Inc. plant in South Sioux City, Neb., where the product is made. USDA officials say several meat producers have asked to indicate use of the product on package labels.

As consumers clamor for more transparency about the beef product dubbed “pink slime,” federal agriculture officials have agreed to allow several meat producers to list the stuff on package labels.

That means grocery shoppers soon could know whether some packages of ground beef contain the ammonia-treated meat that has been at the heart of a controversy that has shuttered plants, scuttled jobs and sparked uproar over the contents of the nation’s hamburgers.

Dirk Fillpot, a spokesman for the U.S. Department of Agriculture’s food safety branch, said Tuesday he could not identify the firms that sought labeling changes, or even say how many were involved. He only confirmed that the agency has received voluntary requests from beef firms to change their labels to indicate it contains lean finely textured beef, or LFTB.

“We’ve determined that such requests will be approved,” Fillpot said.

At least one big beef maker, Cargill Inc., said that firm officials had requested the labeling changes, in part to address the groundswell of consumer concerns.   

“Voluntary labeling is one of the options we are looking at, although no final decision has been made to do this,” said Mike Martin, a Cargill spokesman. “We will also be working with our customers to gather their input to collectively reach mutually acceptable options.”

One advocate who helped launched the controversy said it’s about time consumers' wishes were considered.

“If the product had been labeled from the start, I doubt we’d see anything like the consumer backlash that the media has stirred up in the past few weeks,” said Bettina Elias Siegel, author of the blog “The Lunch Tray,” which helped force agriculture officials to allow schools to opt out of using the beef byproduct in school lunches.

At the heart of the controversy has been the use of an estimated 700 million to 800 million pounds of LFTB, which is added to about 10 billion pounds of ground beef consumed in the U.S. each year, according to the American Meat Institute.

It consists of lean beef carcass trimmings, which have been separated from fat and treated with ammonium hydroxide to kill harmful bacteria such as E. coli O157 and salmonella, before being ground, compressed into blocks and quick-frozen. Cargill treats LFTB differently, using citric acid to change the acidity of the beef to make it inhospitable to pathogens.

Beef Products Inc., the South Dakota firm whose founder, Eldon Roth, created and patented the ammonia process, provided msnbc.com with records that they said showed that raising the pH of the beef from about 5.7, its natural level, to a pH of 8.5 reduces E. coli to undetectable levels.

But the product was dubbed “pink slime” in a 2002 email by a USDA microbiologist who found it distasteful. Concern was raised again recently when celebrity chef Jamie Oliver campaigned against the product being served in school lunches.

Combined with Siegel's quest to get the product out of schools, the current controversy led big U.S. supermarkets, including Safeway Inc., Kroger Co. and Supervalu Inc. to pledge to stop using the products.

It forced BPI to halt production at some of its plants last week, and this week forced another processor, AFA Foods, into bankruptcy.

That’s despite protests from governors of beef-producing states who say the LFTB has been maligned, and top food safety experts, who say that BPI’s product is safe.

“I think their process was validated pretty well,” said Gary Acuff, a microbiologist and director of the Center for Food Safety for Texas A&M college of Agriculture and Life Sciences.

Some experts, such as Michael Osterholm, director of the Center for Infectious Disease Research and Policy and a professor at the University of Minnesota, say LFTB may actually make ground beef a little better.

“If 750,000,000 pounds of relatively safe protein is going into hamburger, it’s got to beat having the same amount of raw product going in,” Osterholm said in an email to msnbc.com.

Much of the contention in scientific circles has centered on whether the ammonia-treated product should actually be considered meat, or whether it should be considered and identified as an additive, said Randall K. Phebus, a professor of food safety and defense at the Food Science Institute at Kansas State University.

Others have urged that labeling products with LFTB should be mandatory. It's not clear whether voluntary measures would provide consumers with adequate information, because some companies might choose to label their products while others would not, some experts suggested. The USDA agreement was first reported on the meat industry online site Meatingplace.com.

Fillpot, of the USDA, said he couldn’t discuss whether the agency was considering making it a requirement. Beef producers who received USDA approval could start changing the labels immediately, agency officials said.

Industry and government leaders have an obligation to help families make informed choices, said Arthur Caplan, a professor of medical ethics at the University of Pennsylvania and a contributor to msnbc.com.

"If consumers want to know information about the food they or their children eat, then manufacturers and grocers ought to find ways to get that information to them," he said, noting it could come through labels, websites, toll-free numbers, pamphlets or even signs at stores. "I believe there is a fundamental right to know all you wish to know about what you eat."

The solution to current crisis will require extraordinary levels of transparency, noted both Bill Marler, a Seattle food safety lawyer, and Doug Powell, a professor of food safety at Kansas State University. Both have urged BPI and others to be as public as possible with their processes, even posting data online that describe how food is processed, produced and handled and the results of safety tests.

On Tuesday, BPI officials appeared to agree with at least part of that, saying that the voluntary labeling change could help rehabilitate the industry’s beleaguered image.

“[It] will be an important first step in restoring consumer confidence in their ground beef,” BPI spokesman Craig Letch wrote in an email to msnbc.com.

Taste tests consistently show that consumers prefer hamburger that contains BPI’s treated product, Letch added.

“We feel this development will allow more customers to provide options to consumers and pave the way for BPI’s lean beef to reestablish its place in the market.”

Related stories:

'Pink slime' panic grows online: Are we overreacting?

McDonald's drops use of gooey 'pink slime' in hamburger meat

Updated March 9: An online petition urging the government to stop the use of "pink slime" -- the scrape and waste meat products that are treated with ammonium-hydroxide -- in school food has collected almost 20,000 signatures over the last several days.

After reports that school districts around the country were serving kids hamburgers containing up to 15 percent of the processed product known in the meat industry as "Lean Finely Textured Beef', parents and consumers poured online to express their disgust. As of Friday afternoon "pink slime" became the most searched phrase on Google Trends and Twitter users were expressing their disgust on #pinkslime.

@mz_gael tweeted, "i don't know when i'll be able to eat hamburger again."

Danielle @danzerotti, a self-described "happily married mother of 4, tweeted "Another reason my 4 kids should be glad that I take the time to prepare their lunches at home every day. As much as I complain."  

"Pink slime" is bits of meat and muscle salvaged from slaughterhouse floors that are treated with a pink chemical to kill any dangerous pathogens. According to an earlier report by msnbc.com, the unappetizing pink goo is widely used in the food industry as an anti-microbial agent in meats and as a leavener in bread and cake products. It's regulated by the U.S. Agriculture Department, which classifies it as "generally recognized as safe." Nevertheless,  McDonald's, have said they are pulling the infamous "pink slime" from their hamburgers.

Although the chemical has been used in ground beef products sold commercially since the 1990s, the sudden concern erupted this week over the USDA's plans to ship 7 million pounds of the processed meat product to schools all over the country. School cafeterias nationwide receive part of the ground beef they serve from the USDA.

The USDA's continued purchase of pink slime for school lunches was first reported Monday by TheDaily.com, which spoke to two former microbiologists at the Food Safety Inspection Service.

"We don't know which districts are receiving what meat, and this meat isn't labeled to show pink slime. They don't have to under federal law," said Bettina Siegal, of TheLunchTray.com earlier this week. Siegal started the petition seeking to ban the ammonia-based waste from school menus. "We should step back and say, 'Why would we feed this to our kid?" said Siegal.

When asked whether the USDA would consider banning "pink slime" from school meat shipments, spokesman Michael Jarvis responded via email: “All USDA ground beef purchases for the National School Lunch Program must meet the highest standards for food safety.  This includes stringent pathogen testing and compliance with all applicable food safety regulations. USDA has strengthened ground beef food safety standards in recent years and only allows products into commerce - and especially into schools -- that we have confidence are safe.”

New York nutritionist and msnbc.com contributor Elisa Zied (@elisazied ) said,"people have a right to know what exactly is in their food, so they can make a judgment whether to eat it or not," but shouldn't panic the meat was unsafe just because of the "yuk" factor. "Like with all food, this idea of pink slime in ground beef does speak to the fact that we need to mix up the foods we consume from all the basic food groups to minimize potentially harmful ingredients and maximize nutrient intake," said Zied.

The processed meat reportedly accounts for 70 percent of all ground beef consumed in the U.S.

KPRC contributed to this report