A sealing jaw (1) for producing sealed packages of a food product from a tube (3) of packaging material, and having a supporting body (11), and a first work surface (27) which interacts, in use, with a second work surface (29) on a further jaw (2) to grip the material to be sealed and perform a sealing operation; one (1) of the jaws (1, 2) defines an anvil (9), and the other (2) of the jaws (1, 2) defines heating means (8); the jaw (1) has connecting means (30) for connecting the first surface (27) to the supporting body (11); the connecting means (30) define a curved third and a curved fourth surface (31, 32) made of rigid material and cooperating mutually to allow the first surface (27) to oscillate with respect to the supporting body (11) when gripping the packaging material prior to the sealing operation.