Abstract: Apparatus and process for cooling unfrozen foodstuff to a desired low temperature below its freezing point, in which a supply of inert gas is used to provide a controlled atmosphere in the freezing chamber; and this controls vapor pressure, dry bulb temperature, wet bulb temperature, and the chemical composition of the atmosphere. A mechanical or refrigerant fluid system supplies the refrigerant effect for lowering the foodstuff's sensible range above freezing, latent heat of fusion, and sensible range below freezing, to the desired temperature sub-freezing sensible heat range.