Abstract: A flexible bag for storage of food products of a configurationally sustaining nature, having somewhat the configuration of a flat segmental portion of a circular disk such as a slice of pizza, provides a peripherally defined triangular body having an interconnected rectilinear neck to define a bag containment chamber. One or both sides of the triangular body provide expandible pleat structures to accommodate food products of differing thickness in the containment chamber. At least one surface of the triangular body or neck provides at least one vent structure having an orifice with an associated closure structure to open to vent heated gas from the containment chamber and close upon cooling of the flexible bag and contents substantially to ambient atmosphere temperature.