It is tapped with a hammer to check the sound that comes from inside the cheese. The sound tells the inspector if the cheese is compact inside, which is correct, or if it has air holes caused by an undesirable strain of bacteria. If cavities are found in the tested cheese, it is rejected. It is sold as unnamed grated cheese or under the name Retinato.
As a final step, a seal is stamped on each roll, guaranteeing the originality of the Parmigiano Reggiano.
