A method of treatment of foodstuffs (A) containing liquids (L 1 ) and air, such as vegetables and mushrooms, comprising a step of a) washing the foodstuffs (A) with a washing liquid (L 2 ), a step of b) draining the foodstuffs (A) and a step of c) removing air from the foodstuffs (A) by applying vacuum. Steps are further provided of d) impregnating the foodstuffs (A) in a closed chamber (5) by applying thereto an atmosphere saturated with an impregnation liquid (L 3 ) and of e) packaging the foodstuffs (A) with a preserving liquid (L 4 ) in a packaging workstation (22). The method further comprises a step of f) steam cooking the foodstuffs (A) in a vessel (11) for at least partially extracting the liquids (L 1 ) contained therein and obtaining a broth (B), a step of g) collecting and storing the broth (B) in a first reservoir (12) connected to the vessel (11) and a step of h) recirculating the broth (B) stored in the first reservoir (12) to the closed chamber (5) of the impregnation step. The impregnation step d) and the packaging step e) are carried out using the broth (B) obtained during the step of cooking f) of batches (Pi) of previous foodstuffs (A) as an impregnation liquid (L 3 ) and as a preserving liquid (L 4 ) respectively.
