Flickr CC/Laurence Simon

A new report shows your favorite Parmesan cheese may contain some ingredients that you might find disconcerting.

Bloomberg News tested store-bought grated cheeses for cellulose, revealing that all of the cheeses tested contained the anti-clumping additive made of wood pulp.

The canister Bloomberg tested of Walmart's Great Value 100% Grated Parmesan Cheese registered 7.8% cellulose, while Jewel-Osco's Essential Everyday 100% Grated Parmesan Cheese clocked in at 8.8%.

Kraft had 3.8%.

"Our repeated testing of this item proves it meets federal regulations for its standard of identity," Walmart spokesperson John Forrest Ales told Business Insider. "Even though using anti-caking aids is common across the industry and approved by the FDA, and testing a single sample is statistically unreliable, our compliance team is looking into these findings with the supplier."

Cheese makers and retailers told Bloomberg they were investigating the test results further.

Cellulose is a safe additive, Bloomberg notes, listed as an ingredient in these "100%" cheeses. However, an acceptable level is 2% to 4%, according to cheese technologist Dean Sommer.

Whole Foods does not list cellulose as an ingredient, but the Whole Foods 365 Parmesan tested at 0.3% cellulose.

The company told Bloomberg it is investigating the matter, but believes the test may have been a false positive.

Cheese makers often mix in higher levels of the wood pulp when making cheese because it is more inexpensive than pure Parmesan.

The FDA is investigating another cheese marker: Castle Cheese Inc.

The company’s president is scheduled this month to plead guilty to pumping products full of cellulose and using cheaper cheddar instead of real Romano.