To solve the problem of the difficulty in cooling a packed food usually to 10°C (50°F) or below because of the embrittlement of a food-containing bag at a low temperature to cause the breakage by stirring, etc., in the conventional packed food cooling system using a cooling conveyor.

In a packed food cooling process using a cooling conveyor 30, a flexible synthetic pack is cooled to 10°C (50°F) or below on the cooling conveyor 30 by ejecting a cooling medium having a freezing point of 0°C (32°F) or below against the bag from plural orifices 44 adjacent to the pack. Brine water or ethylene glycol cooled to 0°C (32°F) or below is used as the cooling medium and the bag 34 is formed of a laminated side wall having at least one layer consisting of a material to cause the breakage and the generation of pinholes and cracks in the case of applying physical stirring, massaging or manual operation during the cooling process and embrittling at 10°C (50°F) or below. The cooling medium is cooled to 0°C (32±F) or below, concretely between 0°C (32°F) and -47°C (-10°F) and ejected through orifices against a bag moving on a conveyor.