A method of pasteurizing and vacuum packing food (2, 3), comprising the following steps: - providing a tray having a first separating barrier dividing the tray into a first compartment and a second compartment, the first compartment having a first flexible bottom, the second compartment having a second flexible bottom and the first barrier having a first channel connecting the first compartment with the second compartment; - placing the food (2, 3) in the first compartment and in the second compartment; - covering the tray with a flexible cover layer to form a package; - providing a one-way valve for one directional communication from the interior of the package to the exterior thereof; - pasteurizing the contents inside the package by means of microwaves; - closing the valve upon pasteurization of the package and allowing the package to cool, whereby a vacuum is created in the package in such a manner that the package with the vacuum-packaged food (2, 3) therein presents a first compartment central portion and a second compartment central portion, wherein, at the first compartment, a distance (d 1) between the flexible cover layer and the first flexible bottom is shorter than a distance (p 1) between the flexible cover layer and the first flexible bottom at the peripheral edges of the first compartment, and wherein, at the second compartment, a distance (d 2) between the flexible cover layer and the second flexible bottom is shorter than a distance (p 2) between the flexible cover layer and the second flexible bottom at the peripheral edges of the second compartment, and thus causing the first flexible bottom to be concave relative the first compartment and the second flexible bottom to be concave relative the second compartment. - providing a tray having a first separating barrier dividing the tray into a first compartment and a second compartment, the first compartment having a first flexible bottom, the second compartment having a second flexible bottom and the first barrier having a first channel connecting the first compartment with the second compartment; - placing the food (2, 3) in the first compartment and in the second compartment; - covering the tray with a flexible cover layer to form a package; - providing a one-way valve for one directional communication from the interior of the package to the exterior thereof; - pasteurizing the contents inside the package by means of microwaves; - closing the valve upon pasteurization of the package and allowing the package to cool, whereby a vacuum is created in the package in such a manner that the package with the vacuum-packaged food (2, 3) therein presents a first compartment central portion and a second compartment central portion, wherein, at the first compartment, a distance (d 1) between the flexible cover layer and the first flexible bottom is shorter than a distance (p 1) between the flexible cover layer and the first flexible bottom at the peripheral edges of the first compartment, and wherein, at the second compartment, a distance (d 2) between the flexible cover layer and the second flexible bottom is shorter than a distance (p 2) between the flexible cover layer and the second flexible bottom at the peripheral edges of the second compartment, and thus causing the first flexible bottom to be concave relative the first compartment and the second flexible bottom to be concave relative the second compartment.