A U.S. Food and Drug Administration (FDA) investigation showed that some popular Parmesan cheese products sold at grocery stores do not actually contain 100 percent grated Parmesan. The agency found out that manufacturer and supplier Castle Cheese Inc. was cutting and substituting the cheese with wood pulp, Bloomberg reports.

The FDA visited the Pennsylvania-based company in 2012 and also learned that some brands supplied by Castle Cheese Inc. have been mislabeled. The cheese products had cellulose in its contents, an additive and anti-clumping agent culled from wood pulp, and it was not indicated in the packaging. While cellulose is generally safe to use in food, the recommended amount should only be 4 percent, according to a cheese technologist via Buzzfeed.

Of the brands, the agency identified Walmart's Great Value 100% Grated Parmesan Cheese as containing 7.8 percent cellulose and Jewel-Osco's Essential Everyday 100% Grated Parmesan Cheese as continuing 8.8 percent cellulose. Kraft's Parmesan contained 3.8 percent cellulose, according to Business Insider.

An independent laboratory also tested the contents of the store-bought brands and discovered that only 40 percent is actual cheese.

"Consumers are innocent, and they're not getting what they bargained for. And that's just wrong," Neil Schuman of Arthur Schuman Inc., a hard Italian cheese company, told Bloomberg. Schuman had long suspected that store-bought Parmesan cheese is not authentic.

In 2013, the FDA sent Castle Cheese Inc. a warning letter citing its violations. By 2014, the company filed for bankruptcy and ceased production, while company president Michelle Myrter is due to face the court this month.