Packaging machine for forming packages filled with a pourable product from a web of packaging material; the packaging machine comprises: - a conveying device configured to advance the web of packaging material along a web advancement path; - a molding apparatus arranged at a molding station for molding molded portions onto the web of packaging material; - a sterilization apparatus for sterilizing the web of packaging material and being arranged at a sterilization station downstream of the molding station along the web advancement path; - an isolation chamber having an inner environment; - a tube forming and sealing device configured to form a tube from the, in use, advancing web of packaging material within the inner environment at a tube formation station arranged downstream of the and to longitudinally seal the tube within the inner environment; - a filling device for filling the tube with the pourable product; - a package forming apparatus configured to form, to transversally seal and to transversally cut the, in use, advancing tube for forming the packages; and - a preserving device configured to preserve the cleanliness and/or sterility of at least the molded portions; wherein the preserving device comprises at least one blowing unit configured to generate a flow of sterile fluid against at least a portion of the web of packaging material while the web of packaging material advances, in use, between the molding station and the sterilization station. the packaging machine comprises: - a conveying device configured to advance the web of packaging material along a web advancement path; - a molding apparatus arranged at a molding station for molding molded portions onto the web of packaging material; - a sterilization apparatus for sterilizing the web of packaging material and being arranged at a sterilization station downstream of the molding station along the web advancement path; - an isolation chamber having an inner environment; - a tube forming and sealing device configured to form a tube from the, in use, advancing web of packaging material within the inner environment at a tube formation station arranged downstream of the and to longitudinally seal the tube within the inner environment; - a filling device for filling the tube with the pourable product; - a package forming apparatus configured to form, to transversally seal and to transversally cut the, in use, advancing tube for forming the packages; and - a preserving device configured to preserve the cleanliness and/or sterility of at least the molded portions; - a conveying device configured to advance the web of packaging material along a web advancement path; - a molding apparatus arranged at a molding station for molding molded portions onto the web of packaging material; - a sterilization apparatus for sterilizing the web of packaging material and being arranged at a sterilization station downstream of the molding station along the web advancement path; - an isolation chamber having an inner environment; - a tube forming and sealing device configured to form a tube from the, in use, advancing web of packaging material within the inner environment at a tube formation station arranged downstream of the and to longitudinally seal the tube within the inner environment; - a filling device for filling the tube with the pourable product; - a package forming apparatus configured to form, to transversally seal and to transversally cut the, in use, advancing tube for forming the packages; and - a preserving device configured to preserve the cleanliness and/or sterility of at least the molded portions; wherein the preserving device comprises at least one blowing unit configured to generate a flow of sterile fluid against at least a portion of the web of packaging material while the web of packaging material advances, in use, between the molding station and the sterilization station.