Laboratory tests have found many brands of grated Parmesan and Romano cheeses contain higher than expected amounts of wood cellulose.

An independent laboratory was hired by Bloomberg News to test popular brands of store-bought grated cheese to learn how much wood pulp each cheese contained. Wood pulp, which primarily consists of cellulose, is a relatively safe, common additive that helps prevent clumping. The lab found, however, that a number of the cheeses exceeded the typical industry standard, which according to Dean Sommer, a cheese technologist at the Center for Dairy Research in Madison, Wisconsin, is between 2 and 4 percent.

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Here's how cheeses measure up in Bloomberg's findings: Essential Everyday 100% Grated Parmesan Cheese, from Jewel-Osco, was 8.8 percent cellulose, while Wal-Mart Stores Inc.’s Great Value 100% Grated Parmesan Cheese registered 7.8 percent. Whole Foods 365 brand didn’t list cellulose as an ingredient on the label, but still tested at 0.3 percent. Kraft had 3.8 percent.

Bloomberg hired the independent lab after learning that in 2012, Castle Cheese Inc. was doctoring 100 percent of its cheese with substitutes like wood pulp and other fillers and then distributing it to the nation's largest grocery chains. Castle's president Michelle Myrter is expected to plead guilty to charges and faces up to a year in prison.

Bloomberg talked with Neil Schuman, head of Arthur Schuman Inc., the nation’s largest seller of hard Italian cheeses, who has stood against what he calls the “grated cheese fraud.”

“We’re often not even competing against cheese,” he said. “Time and again we find grated ‘Parmesan’ and ‘Romano’ available on the market that only partially consists of real cheese. The rest most often includes cellulose, imitation cheeses, potato starch and analog cheese.”

In a 2015 essay for Dairy Foods, Schuman said it’s a widespread problem. Schuman says:

In a recent random sampling of dry grated cheeses for sale at retailers in Wisconsin, we found ‘Parmesan’ canisters that had more than 25 percent cellulose in them, and others that were two-thirds carbohydrates. And according to recent tests, this problem is even more pronounced in the foodservice and ingredient channels. As the category leader, we feel a responsibility to address this condition. It’s fraud and it’s illegal. And it’s undermining the market for real cheese.

Other in-store foods containing cellulose may include pancakes, syrup, waffles, chicken nuggets, ice cream, and other desserts. Nautritionists say there is no real danger in wood cellulose –  a fiber found in fruits and vegetables, and that it’s the most abundant organic compound found on earth.