Apparently the "100 per cent parmesan" claim on grated cheese in U.S. stores is not true -- the popular pasta topper also includes processed wood.

That is what Marc Moschetta has claimed in a lawsuit filed Tuesday against U.S. retail titan Wal-Mart Stores, and Samantha Lewin alleged in her San Francisco suit against food giant Kraft last week.

Both suits say that the labels on the two companies' finely grated parmesan, claiming the contents are "100 per cent grated parmesan," are untrue and deceptive.

"Independent testing shows that at least seven per cent to 10 per cent of the product is not parmesan cheese," Moschetta said in his suit, filed in a U.S. federal court in New York.

"In fact, at least seven per cent to 10 per cent of the product is cellulose, an anti-clumping agent derived from wood chips."

Moschetta, alleging that consumers are deceived by the 100 per cent claim, said he would not have bought the cheese "at a premium price, and/or would have paid significantly less for the product, had he known that the '100 per cent' representation is false."

The lawsuit depicts an eight-ounce (227 gram) jar of Walmart "100 per cent grated parmesan," which the retail chain sells for US$2.98.

Lewin made a similar claim against Kraft, saying testing showed 3.8 per cent cellulose in its $3.99 jar of "100 per cent parmesan."

Both lawsuits seek class-action status to represent damages to all consumers allegedly deceived by the makers' claims. According to the San Francisco filing, the minimum aggregate claim in a class-action suit would be $5 million.