Supermarket chains Kroger Co. and Stop & Shop said Thursday they will join the growing list of store chains that will no longer sell beef that includes an additive with the unappetizing moniker "pink slime."

Federal regulators say the ammonia-treated filler, known in the industry as "lean, finely textured beef," meets food safety standards. But critics say the product could be unsafe and is an unappetizing example of industrialized food production.

The Kroger Co., the largest traditional grocer, with 2,435 supermarkets in 31 states, said it will stop buying the beef, reversing itself after saying Wednesday it would sell beef both with and without the additive.

Stop & Shop said that while the U.S. Department of Agriculture has said the product is safe for consumption, it will stop selling the beef because of customer concerns. Stop & Shop is a unit of Dutch supermarkets owner Royal Ahold NV and operates 400 stores in the Northeast United States.

The chains joined Safeway, Supervalu and Food Lion, among others, who have said they won't sell beef with the filler.

"Our customers have expressed their concerns that the use of lean finely textured beef -- while fully approved by the USDA for safety and quality -- is something they do not want in their ground beef," Kroger said.

The low-cost ingredient is made from fatty bits of meat left over from other cuts.

The term "pink slime" has been used pejoratively for at least several years, but it wasn't until early March that social media exploded with worry and an online petition seeking its ouster from schools lit up, quickly garnering hundreds of thousands of supporters.

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