Clamshell packaging for airtight packaging of foodstuff

A clamshell packaging for airtight packaging of foodstuff, the packaging comprising:

• a tray folded out of a single sheet of material, the tray having at least two adjacent pool parts, each pool part having a bottom wall and upstanding walls arranged around the perimeter edge of the bottom wall;
• a circumferential, horizontal flange arranged to the tray to at least some upper edges of the upstanding walls;
• and
• a plastic barrier foil arranged in the at least two adjacent pool parts and extending onto and substantially covering the circumferential, horizontal flange,
• wherein the at least two adjacent pool parts are hingedly connected to each other along an upper edge of a respective upstanding wall, such that the at least two adjacent pool parts can be hinged on top of each other to form a closed box,
• wherein the circumferential, horizontal flange comprises a seal zone extending along the full length of the flange, wherein the seal zone is line symmetrical along a hinge line at the upper edge of the connected walls, and
• wherein the circumferential, horizontal flange is composed out of a number of abutting flange parts, each flange part being arranged to a respective upper edge of an upstanding wall, and wherein each transition of two abutting edges of the number of abutting flange parts are positioned asymmetrically along the hinge line, such that none of the transitions overlap with each other when the at least two adjacent pool parts are hinged on top of each other.