The US government said Thursday it will leave it to schools to decide whether to use a controversial ground-beef filler in the meals they serve to students. In a statement, the Department of Agriculture (USDA) acknowledged public concern over lean finely textured beef, popularly known as "pink slime," in its National School Lunch Program. Made from beef trimmings otherwise used in pet food and cooking oil, and treated with a puff of ammonia to deter e.coli bacteria, lean finely textured beef is typically added to ground meat, like hamburger, as a low-cost filler. USDA recently bought seven million pounds (3.6 million kilograms) of the rosy-colored product for school meals -- prompting more than 220,000 consumers to sign an online petition demanding a halt to its use in school food. "Due to customer demand, the department will be adjusting procurement specifications for the next school year so schools can have additional options in procuring ground beef products," the department said. "USDA will provide schools with a choice to order product either with or without lean finely textured beef. It went on to invite consumers "to consult science-based information" attesting to the safety and quality of pink slime, which critics say is present in 70 percent of ground beef sold in US supermarkets. The National School Lunch Program feeds more than 31 million school children, many of them from low-income families. In an email to AFP, Bettina Siegel, who started the petition on www.change.org, said: "I am incredibly gratified that USDA heard our concerns about so-called pink slime in school meals and changed its school food purchasing policy to allow choice." "Right now I'm asking more questions to just make sure this is a meaningful solution for (school) districts, or if there's more work to be done," added Siegel, who blogs about school meals at www.thelunchtray.com.