Macinata a pietra 

Stone-ground Petra flours are produced with stone millstones inserted in an industrial process, where the grinding begins with the crushing of the grain between the rotating stones and continues between cylinders cast iron (to date there is no technology that makes it possible to organize a grinding industrial stone only) , with subsequent grinding steps and shortening, which separate and then reassemble the different parts of the grain of wheat to bring back the finished product in two of the types of law (type 1 and integral type).

Petra 1, 3, 5, and 9 flours are declared "stone ground" to differentiate them from the cylinder-milled ones and to highlight that the first step in the stone grinding wheels conditions the final result of a seamless milling process, which, in the absence of the second phase and the preliminary industrial optical selection of healthy grains would deprive them stone-ground flours of the required bread-making and food safety characteristics by law and by modern bakery artisans.