A valve assembly is provided for venting pressurized gases generated from within an enclosed package during a heating of the package. The valve assembly has a membrane element, a tubular body and a retaining member. The tubular body has an open end, a closed end and a recess defined therebetween. The closed end has an aperture for venting the pressurized gases therethrough. The recess is operative to receive and support the membrane element adjacent the closed end. The retaining member is operative for snap-fit engagement with the tubular body for retaining the membrane element within the recess.