A cap liner comprising: a disc-shaped venting cap liner body having a bottom surface facing an annular bottle lip surrounding an open top end of a bottle neck, and a top surface facing an inner top wall of a closure cap, the body being configured to provide a gas-permeable but liquid-impervious seal that is resistant to rupture when a downwardly directed application torque is applied in a thickness direction of the liner body to compression seal the liner body between the annular bottle lip and the inner top wall of the cap to form a sealed bottle, the cap liner body including top and bottom layers (34, 28) wherein: (a) the bottom layer comprises a mineral-filler based polyolefin material having a lower surface configured to compression seal to the annular bottle lip and an upper surface bonded to a non-grooved lower surface of the top layer, wherein the MFP material layer is substantially liquid-impervious while allowing release of gas evolving from a liquid product in the sealed bottle; and (b) the top layer comprises a polyolefin foam material having a grooved upper surface with channels facing the inner top wall of the cap, and a plurality of through-holes extending in a thickness direction of the PO foam material between the grooved upper and non-grooved lower surfaces (36, 38) of the top layer to allow gas, evolving from a product in the sealed bottle, to permeate out the open top end of the bottle neck, through the MFP material and the through-holes of the PO foam material, and along the channels in the grooved upper surface of the top layer (340, allowing the gas to then flow out of a peripheral area disposed between an outer surface of the bottle neck and a peripheral cap flange extending downwardly from the inner top wall of the cap. a disc-shaped venting cap liner body having a bottom surface facing an annular bottle lip surrounding an open top end of a bottle neck, and a top surface facing an inner top wall of a closure cap, the body being configured to provide a gas-permeable but liquid-impervious seal that is resistant to rupture when a downwardly directed application torque is applied in a thickness direction of the liner body to compression seal the liner body between the annular bottle lip and the inner top wall of the cap to form a sealed bottle, the cap liner body including top and bottom layers (34, 28) wherein: (a) the bottom layer comprises a mineral-filler based polyolefin material having a lower surface configured to compression seal to the annular bottle lip and an upper surface bonded to a non-grooved lower surface of the top layer, wherein the MFP material layer is substantially liquid-impervious while allowing release of gas evolving from a liquid product in the sealed bottle; and (b) the top layer comprises a polyolefin foam material having a grooved upper surface with channels facing the inner top wall of the cap, and a plurality of through-holes extending in a thickness direction of the PO foam material between the grooved upper and non-grooved lower surfaces (36, 38) of the top layer to allow gas, evolving from a product in the sealed bottle, to permeate out the open top end of the bottle neck, through the MFP material and the through-holes of the PO foam material, and along the channels in the grooved upper surface of the top layer (340, allowing the gas to then flow out of a peripheral area disposed between an outer surface of the bottle neck and a peripheral cap flange extending downwardly from the inner top wall of the cap. (a) the bottom layer comprises a mineral-filler based polyolefin material having a lower surface configured to compression seal to the annular bottle lip and an upper surface bonded to a non-grooved lower surface of the top layer, wherein the MFP material layer is substantially liquid-impervious while allowing release of gas evolving from a liquid product in the sealed bottle; and (b) the top layer comprises a polyolefin foam material having a grooved upper surface with channels facing the inner top wall of the cap, and a plurality of through-holes extending in a thickness direction of the PO foam material between the grooved upper and non-grooved lower surfaces (36, 38) of the top layer to allow gas, evolving from a product in the sealed bottle, to permeate out the open top end of the bottle neck, through the MFP material and the through-holes of the PO foam material, and along the channels in the grooved upper surface of the top layer (340, allowing the gas to then flow out of a peripheral area disposed between an outer surface of the bottle neck and a peripheral cap flange extending downwardly from the inner top wall of the cap.