Apparatus for aerating a pasty product and for mixing with another product

17-19. (canceled)

A method for aerating a pasty product comprising passing a stream of pasty product to be aerated through an apparatus, the apparatus comprising a housing extending in a longitudinal direction, the housing comprising an inlet for the pasty product to be aerated and an outlet for the aerated product, within the housing, at least a first set of a rotor and a stator and a second set of a rotor and a stator, wherein each set of a rotor and a stator has complementary toothed rims oppositely orientated in the longitudinal direction, the apparatus comprising a drive shaft, the rotors of each set of a rotor and a stator being coupled to said drive shaft, the apparatus further comprising a gas injector for injecting, upstream of the first set of a rotor and a stator, a gas into the pasty product to be aerated, and the apparatus comprises an intermediate mixing chamber provided in the housing between the first and the second sets of a rotor and a stator, and a secondary product introduction member which protrudes into the intermediate mixing chamber so as to issue into said intermediate mixing chamber, injecting via the upstream gas injector a gas into the pasty product stream at a position upstream relative to the first set of a rotor and a stator, and injecting a secondary product via the secondary product introduction means into the intermediate mixing chamber.