Methods are disclosed of assembling a food package using an absorbent pad having an active agent that generates an atmosphere-modifying gas into the headspace after the food package is sealed, to compensate for losses of atmosphere-modifying gases injected in the food package prior to sealing. The methods of assembly reduce the headspace requirements and overall dimensions of the food package. The methods further prevent or reduce collapse of the food package or having the lid film contact the food product.
